Infectious Disease and Microbiology – Haemophilus influenzae

Overview

Haemophilus influenzae is a small Gram-negative coccobacillus that can cause both invasive and mucosal disease. Clinically, it is useful to distinguish encapsulated strains, especially serotype b (Hib), from nonencapsulated or nontypeable strains.

Before widespread Hib vaccination, H. influenzae type b was a major cause of meningitis, epiglottitis, bacteremia, cellulitis, and septic arthritis in children. Vaccination has dramatically reduced these invasive childhood infections.

Microbiologic Characteristics

H. influenzae is:

• A small Gram-negative coccobacillus

• Facultatively anaerobic

• Fastidious in culture

• Capable of existing as encapsulated or nonencapsulated strains

A classic laboratory feature is its requirement for:

Factor X = hemin

and

Factor V = NAD

for growth.

Culture Characteristics

H. influenzae grows well on:

Chocolate agar

because heating of blood releases the required X and V factors.

It may also demonstrate the satellitism phenomenon when growing near organisms such as Staphylococcus aureus, which supply growth factors.

Incubation Period

For invasive disease such as meningitis, the incubation period is not precisely established, but the source supports approximately:

2–4 days

Epidemiology

H. influenzae occurs worldwide.

The epidemiology changed markedly after introduction of conjugate vaccines against Hib.

Routine Hib immunization has produced a dramatic reduction in invasive serotype b disease in vaccinated populations.

Encapsulated H. influenzae Type b

Importance of the Capsule

The polysaccharide capsule, particularly the serotype b capsule, is a major virulence factor.

Hib can invade the bloodstream and disseminate to normally sterile sites, causing severe disease especially in young children.

Invasive Hib Disease in Children

Classically, Hib causes:

• Meningitis

• Epiglottitis

• Cellulitis

• Septic arthritis

• Bacteremia

These infections are often associated with bloodstream invasion.

Hib Meningitis

Before widespread vaccination, Hib was one of the major causes of bacterial meningitis in young children.

Clinical manifestations may include:

• Fever

• Irritability

• Lethargy

• Vomiting

• Neck stiffness

• Altered mental status

• Seizures in severe disease

This presentation is now much less common in appropriately vaccinated populations.

Epiglottitis

Hib is classically associated with acute epiglottitis, particularly in unvaccinated children.

Typical findings include:

• Abrupt fever

• Severe sore throat

• Dysphagia

• Drooling

• Muffled voice

• Inspiratory stridor

• Respiratory distress

A child may sit in a tripod position to maximize airway patency.

Epiglottitis – Airway Emergency

The major danger of epiglottitis is:

Rapid upper-airway obstruction

Therefore, airway management takes priority over attempts to directly examine the throat in a patient with severe suspected epiglottitis.

Nontypeable H. influenzae

Overview

Nonencapsulated strains, commonly called nontypeable H. influenzae (NTHi), more often cause localized mucosal respiratory infections.

These infections are particularly common in older children and adults.

Otitis Media

Nontypeable H. influenzae is an important cause of:

Acute otitis media

especially in children.

Sinusitis

Nontypeable strains also commonly contribute to:

Acute bacterial sinusitis

often alongside organisms such as Streptococcus pneumoniae and Moraxella catarrhalis.

Chronic Bronchitis and COPD Exacerbation

In adults, particularly those with chronic airway disease, nontypeable H. influenzae may cause:

• Acute exacerbations of chronic bronchitis

• COPD exacerbations

• Lower respiratory tract infection

Pneumonia

H. influenzae may cause pneumonia, particularly in:

• Older adults

• Patients with chronic lung disease

• Immunocompromised individuals

Nontypeable strains are particularly important in adult respiratory infections.

Bacteremia

Although invasive bloodstream infection is classically associated with encapsulated strains, bacteremia can occasionally occur with nonencapsulated strains as well.

Severe Infection in Asplenic Patients

Patients with absent or impaired splenic function are at increased risk for severe infections from encapsulated organisms.

Thus, H. influenzae can produce:

Rapidly progressive sepsis

in patients with:

• Anatomic asplenia

• Functional asplenia

The clinical course can be fulminant.

Epididymitis and Orchitis

The source also lists:

• Epididymitis

• Orchitis

as uncommon manifestations of H. influenzae infection.

Diagnosis

The source describes antigen detection methods including:

• Coagglutination

• Counterimmunoelectrophoresis

• Latex agglutination

These techniques can detect bacterial antigen in secretions or sterile body fluids.

Modern Diagnostic Approach

Depending on the clinical syndrome, diagnosis may also include:

• Culture

• Blood cultures

• CSF culture

• Respiratory specimen culture

• PCR or other molecular testing

For invasive disease, culture and molecular methods are generally more informative than older antigen-detection techniques alone.

Treatment

The source lists:

Amoxicillin–clavulanate

or

Second- or third-generation cephalosporins

as treatment options.

Selection depends on the site and severity of infection.

Invasive Disease

For serious invasive infections such as meningitis, a third-generation cephalosporin, such as ceftriaxone or cefotaxime, is typically an important therapeutic choice.

β-lactamase production and other resistance mechanisms can make plain ampicillin or amoxicillin unreliable without susceptibility information.

Additional Treatment

The source lists:

• Trimethoprim–sulfamethoxazole

• Fluoroquinolones

• Azithromycin

• Aztreonam

• Imipenem

• Meropenem

Choice should be guided by the infection site, severity, patient factors, and susceptibility results.

β-Lactamase Production

Some H. influenzae strains produce β-lactamase, resulting in resistance to ampicillin and amoxicillin.

Therefore:

Amoxicillin alone may fail

whereas:

Amoxicillin–clavulanate

can overcome many β-lactamase-producing strains.

Prevention

Hib Conjugate Vaccine

The most important preventive measure is:

Hib conjugate vaccination

The vaccine contains capsular polysaccharide linked to a protein carrier, allowing an effective immune response in young children.

It is highly effective and has dramatically reduced invasive Hib disease.

Age for Vaccination

The source notes effective vaccination in children older than:

2 months

which corresponds to the age at which routine infant Hib immunization programs begin in many countries.

Postexposure Prophylaxis

Close contacts of a patient with invasive Hib disease may require antimicrobial prophylaxis under appropriate public-health circumstances.

The classic drug is:

Rifampin

The source also mentions ciprofloxacin as a protective measure.

Who May Need Prophylaxis?

Postexposure prophylaxis is particularly considered for selected:

• Household contacts

• Childcare contacts

• Individuals in environments containing incompletely vaccinated or vulnerable young children

Public-health recommendations should guide who receives prophylaxis.

High-Yield Clinical Pattern – Hib

Unvaccinated young child

• ●

Fever

• ●

Meningitis, epiglottitis, cellulitis, or septic arthritis

• ●

Bacteremia

→ Think Haemophilus influenzae type b

High-Yield Clinical Pattern – Nontypeable H. influenzae

Adult with chronic lung disease

• ●

COPD/chronic bronchitis exacerbation

or

Child with otitis media or sinusitis

→ Think nontypeable H. influenzae

Classic Laboratory Pattern

Small Gram-negative coccobacillus

• ●

Requires factor X and factor V

• ●

Grows on chocolate agar

→ Think Haemophilus influenzae

Hib vs. Nontypeable H. influenzae

Hib:

Encapsulated → invasive disease → meningitis, epiglottitis, bacteremia, septic arthritis

Nontypeable strains:

No capsule → mucosal respiratory disease → otitis, sinusitis, bronchitis/COPD exacerbation, pneumonia

Exam Essentials

Organism: Haemophilus influenzae

Type: Gram-negative coccobacillus

Growth requirements: Factors X and V

Culture medium: Chocolate agar

Major virulence factor of Hib: Polysaccharide capsule

Important serotype: Type b

Incubation for invasive disease: Approximately 2–4 days

Hib infections: Meningitis, epiglottitis, bacteremia, cellulitis, septic arthritis

Nontypeable infections: Otitis media, sinusitis, bronchitis/COPD exacerbation, pneumonia

High-risk group for fulminant sepsis: Asplenic patients

Diagnosis: Culture, molecular testing; antigen detection historically used

Treatment: Amoxicillin–clavulanate for appropriate mucosal disease; third-generation cephalosporins for serious invasive disease

Resistance mechanism: β-lactamase production

Prevention: Hib conjugate vaccine

Postexposure prophylaxis: Rifampin for selected close contacts

Key clinical pearl: Haemophilus influenzae type b is an encapsulated invasive pathogen classically associated with meningitis and epiglottitis in unvaccinated children, whereas nontypeable strains primarily cause otitis media, sinusitis, COPD exacerbations, and pneumonia. The organism requires factors X and V and classically grows on chocolate agar.

Infectious Disease and Microbiology – Haemophilus ducreyi

Overview

Haemophilus ducreyi is an aerobic Gram-negative coccobacillus that causes chancroid, a sexually transmitted infection characterized by painful genital ulcers with tender inguinal lymphadenopathy.

The disease is more common in tropical and subtropical regions, although outbreaks have also occurred in the United States.

Microbiologic Characteristics

Haemophilus ducreyi is:

• A Gram-negative coccobacillus

• Aerobic

• Fastidious and relatively difficult to culture

• The causative organism of chancroid

Its fastidious growth requirements explain why culture requires special media.

Incubation Period

The incubation period is usually:

3–5 days

but may occasionally extend to:

Up to 2 weeks

Symptoms typically begin with a papule that progresses to a painful ulcer.

Epidemiology

Chancroid is more common in:

• Tropical regions

• Subtropical regions

• Areas with limited access to sexually transmitted infection control services

Historically, outbreaks have occurred in the United States, including among inner-city populations and migrant agricultural workers.

The source notes that men are more commonly affected.

Transmission

H. ducreyi is transmitted primarily through:

Sexual contact

Infection occurs when the organism gains access through small breaks in genital or perigenital skin and mucosa.

Chancroid

The classic infection is:

Chancroid

This is a genital ulcerative disease characterized by:

• Painful genital ulceration

• Tender regional lymphadenopathy

• Possible suppurative inguinal lymph nodes

The ulcer is typically more painful and inflammatory than the chancre of primary syphilis.

Genital Ulcer

A typical chancroid ulcer is:

• Painful

• Soft rather than indurated

• Irregular in shape

• Surrounded by inflammation

• Often associated with purulent or necrotic material

This appearance contrasts with the typically painless ulcer of primary syphilis.

Inguinal Adenopathy

Tender inguinal lymphadenopathy is a characteristic feature.

Affected lymph nodes may:

• Become enlarged

• Be painful

• Become fluctuant

• Suppurate

A fluctuant suppurative lymph node is often called a:

Bubo

Chancroid vs. Syphilis

Chancroid –

H. ducreyi

Painful ulcer

• ●

Tender inguinal lymphadenopathy

• ●

Soft, irregular ulcer

Primary Syphilis –

Treponema pallidum

Usually painless chancre

• ●

Typically nontender lymphadenopathy

This distinction is highly useful clinically and for examinations.

Chancroid vs. Genital Herpes

Both chancroid and genital herpes can cause painful genital ulcers.

However:

Chancroid

→ Often a deeper, irregular ulcer with purulent base and tender adenopathy

Genital herpes

→ Often begins with clusters of painful vesicles that ulcerate

Laboratory testing is important when the diagnosis is uncertain.

Diagnosis

The source lists:

Culture using special media

Because H. ducreyi is fastidious, culture can be technically difficult and may have limited sensitivity.

Diagnosis therefore often depends on clinical findings combined with exclusion or testing for other causes of genital ulcer disease.

Differential Diagnosis of Genital Ulcers

Important causes include:

• Haemophilus ducreyi → chancroid

• Treponema pallidum → syphilis

• Herpes simplex virus → genital herpes

• Chlamydia trachomatis L1–L3 → lymphogranuloma venereum

• Klebsiella granulomatis → granuloma inguinale

Treatment

The source lists:

Ceftriaxone 250 mg IM as a single dose

or

Azithromycin 1 g as a single dose

or

Ciprofloxacin 500 mg orally every 12 hours for 3 days

These are classic treatment regimens for chancroid.

Additional Treatment

Additional treatments listed in the source include:

• Erythromycin

• Trimethoprim–sulfamethoxazole

• Ofloxacin

Choice of therapy should take into account current recommendations, local susceptibility patterns, pregnancy status, and drug interactions.

Management of Fluctuant Inguinal Nodes

If inguinal adenopathy becomes:

Fluctuant

and especially if it is large,

the source recommends:

Needle aspiration

Drainage can relieve discomfort and reduce the risk of spontaneous rupture.

Prevention

General prevention includes:

Safe-sex practices

This includes:

• Consistent barrier protection

• Reduction of high-risk sexual exposure

• Evaluation and treatment of sexual partners when appropriate

• Testing for other sexually transmitted infections

Important STI Association

Patients with chancroid should also be evaluated for other sexually transmitted infections because genital ulcers can increase the risk of acquisition and transmission of infections such as HIV.

High-Yield Clinical Pattern

Recent sexual exposure

• ●

Incubation of about 3–5 days

• ●

Painful genital ulcer

• ●

Tender inguinal lymphadenopathy or bubo

→ Think Haemophilus ducreyi causing chancroid

Exam Essentials

Organism: Haemophilus ducreyi

Type: Gram-negative coccobacillus

Major disease: Chancroid

Transmission: Sexual contact

Incubation: Usually 3–5 days

Geography: More common in tropical and subtropical regions

Genital ulcer: Painful, soft, irregular

Lymph nodes: Tender inguinal adenopathy, sometimes fluctuant

Suppurative node: Bubo

Diagnosis in source: Culture on special media

Treatment in source: Ceftriaxone, azithromycin, or ciprofloxacin

Large fluctuant node: Needle aspiration

Prevention: Safe-sex practices

Classic distinction: Chancroid is painful; primary syphilis is usually painless

Key clinical pearl: Haemophilus ducreyi causes chancroid, classically presenting as a painful soft genital ulcer with tender inguinal lymphadenopathy or buboes. The painful ulcer is the major clue distinguishing chancroid from the typically painless chancre of primary syphilis.

Infectious Disease and Microbiology – Gnathostoma spinigerum

Overview

Gnathostoma spinigerum is a parasitic nematode (roundworm) that normally infects dogs and cats. Humans are accidental hosts and develop gnathostomiasis after ingesting infective larvae, classically in raw or undercooked fish or other intermediate/paratenic hosts.

A characteristic manifestation is intermittent migratory, pruritic subcutaneous swelling accompanied by peripheral eosinophilia. Larval migration into the central nervous system or eye can produce severe neurologic or ocular disease.

Microbiologic Characteristics

Gnathostoma spinigerum is:

• A nematode helminth

• Primarily a parasite of dogs and cats

• Acquired by humans through ingestion of infective larvae

• Characterized in humans by tissue migration of larvae

Humans are generally accidental hosts in whom the parasite does not complete its normal life cycle.

Epidemiology

Gnathostomiasis is particularly associated with:

• Thailand

• Japan

• China

• Other parts of Southeast Asia

The source notes that many reported cases have historically come from Thailand.

Transmission

Human infection is most commonly acquired through ingestion of raw or inadequately cooked food containing infective larvae.

Important exposures include:

• Raw or undercooked freshwater fish

• Poultry and other potential paratenic hosts

Thus, dietary history can provide an important diagnostic clue.

Life Cycle in Humans

After infective larvae are swallowed:

Ingestion of larvae

→

Penetration of the gastrointestinal tract

→

Migration through tissues

→

Inflammatory and eosinophilic response

Because humans are accidental hosts, larvae may continue migrating rather than developing normally into mature adult worms.

Gnathostomiasis

The disease caused by Gnathostoma is called:

Gnathostomiasis

The characteristic clinical feature is migratory tissue disease caused by movement of larvae through different parts of the body.

Cutaneous Gnathostomiasis

The classic presentation consists of:

Transient, migratory, pruritic erythematous swelling

The lesions may:

• Appear suddenly

• Be intensely pruritic

• Become erythematous and edematous

• Disappear and recur elsewhere

• Reflect migration of the larva through subcutaneous tissues

This recurrent migratory pattern is highly suggestive in an appropriate epidemiologic setting.

Eosinophilia

Peripheral eosinophilia is an important laboratory finding.

The combination of:

Migratory subcutaneous swelling

• ●

Eosinophilia

• ●

History of raw or undercooked fish consumption in an endemic region

should strongly suggest gnathostomiasis.

Neurologic Gnathostomiasis

Larvae may migrate into the central nervous system, producing potentially serious neurologic disease.

Manifestations can include:

• Focal cerebral lesions

• Meningitic or meningoencephalitic manifestations

• Radicular symptoms

• Other focal neurologic abnormalities

Neurologic involvement is one of the most serious complications.

Cerebrospinal Fluid Findings

An important clue in CNS gnathostomiasis is:

Eosinophilic pleocytosis of the CSF

Therefore:

Neurologic symptoms + CSF eosinophilia + compatible dietary/travel exposure

→ Consider a tissue-invasive helminth such as Gnathostoma spinigerum.

Eosinophilic Meningitis

Because larvae can invade the nervous system, gnathostomiasis is an important parasitic cause of eosinophilic meningitis or meningoencephalitis.

The differential diagnosis of eosinophilic meningitis also includes other helminthic infections, particularly Angiostrongylus cantonensis.

Ocular Gnathostomiasis

Larvae may occasionally migrate into the eye.

Ocular infection can cause:

• Ocular inflammation

• Visual disturbances

• Pain

• Visible or migrating intraocular parasite

When technically possible, removal of the parasite may be both diagnostic and therapeutic.

Diagnosis

The source describes definitive diagnosis by:

Extraction and identification of the parasite

Demonstration of the actual larva provides direct confirmation of infection.

Clinical Diagnosis

Because recovery of the parasite is not always possible, suspicion may arise from the combination of:

Compatible exposure

• ●

Migratory cutaneous lesions

• ●

Peripheral eosinophilia

or

Neurologic disease with CSF eosinophilia

The epidemiologic history is therefore particularly important.

Treatment

The source notes that the effectiveness of antihelminthic therapy was historically uncertain but that treatment was commonly administered.

It lists:

Albendazole 400 mg orally every 12 hours for 14 days

as a treatment regimen.

Additional Treatment

The source reports successful treatment of ocular disease using:

Mebendazole

However, when an accessible worm is present—particularly in ocular or superficial disease—physical extraction of the parasite may play an important role.

Prevention

Prevention primarily involves avoiding ingestion of viable larvae.

Important measures include:

• Thoroughly cooking freshwater fish

• Avoiding raw or inadequately cooked potential intermediate/paratenic hosts

• Following safe food-preparation practices in endemic regions

High-Yield Clinical Pattern

Travel/residence in Southeast Asia

• ●

Raw or undercooked freshwater fish exposure

• ●

Recurrent migratory pruritic subcutaneous swelling

• ●

Peripheral eosinophilia

→ Think Gnathostoma spinigerum

Neurologic High-Yield Pattern

Compatible food exposure

• ●

Neurologic symptoms

• ●

Focal CNS abnormalities

• ●

Eosinophilic pleocytosis in CSF

→ Consider neurognathostomiasis

Exam Essentials

Organism: Gnathostoma spinigerum

Type: Nematode helminth

Natural definitive hosts: Dogs and cats

Human role: Accidental host

Major geographic association: Southeast Asia, particularly Thailand

Transmission: Ingestion of infective larvae in raw/undercooked food, classically freshwater fish

Pathogenesis: Larval tissue migration

Classic manifestation: Migratory pruritic erythematous subcutaneous swelling

Major laboratory clue: Eosinophilia

CNS complication: Neurognathostomiasis

CSF finding: Eosinophilic pleocytosis

Ocular disease: Possible through larval migration

Definitive diagnosis: Extraction and identification of parasite

Treatment in source: Albendazole 400 mg q12h for 14 days

Additional historical therapy: Mebendazole for ocular disease

Prevention: Avoid raw or undercooked potential intermediate/paratenic hosts

Key clinical pearl: Gnathostoma spinigerum should be strongly suspected when a patient with raw freshwater fish exposure in Southeast Asia develops recurrent migratory pruritic subcutaneous swellings with eosinophilia. CNS migration can cause eosinophilic meningitis or focal neurologic disease.

Infectious Disease and Microbiology – Geotrichum candidum

Overview

Geotrichum candidum is a filamentous fungus with septate hyphae that can produce arthroconidia in infected tissue. Human infection, sometimes referred to as geotrichosis, is rare but occurs worldwide.

The most important severe manifestation is disseminated infection in profoundly immunocompromised patients, particularly those with neutropenia.

Microbiologic Characteristics

Geotrichum candidum is characterized by:

• Filamentous fungal growth

• Septate hyphae

• Hyaline rather than pigmented hyphae

• Formation of arthroconidia (arthrospores)

In tissue, the characteristic appearance is:

Septate hyaline hyphae + arthroconidia

Arthroconidia

Arthroconidia are produced by fragmentation of fungal hyphae into individual rectangular or barrel-shaped cells.

Recognition of arthroconidia can provide an important clue to the identity of an arthroconidial fungus.

However, this morphology is not unique to Geotrichum, so culture and definitive organism identification remain important.

Epidemiology

Human infection is:

Rare

but has been reported worldwide.

Geotrichum organisms can be encountered in the environment, and colonization of human mucosal surfaces may occur without invasive disease.

Therefore, isolation of the organism does not automatically prove invasive infection.

Risk Factors

The most important risk factor for severe invasive disease is:

Profound neutropenia

Other states of significant immunosuppression may also increase the risk of invasive fungal disease.

Disseminated Geotrichosis

The major invasive manifestation described in the source is:

Disseminated disease in neutropenic patients

Once invasive infection develops, organisms may spread hematogenously and involve multiple organs.

This is a serious opportunistic fungal infection.

Clinical Pattern

The typical high-risk setting is:

Severely immunocompromised patient

• ●

Prolonged neutropenia

• ●

Persistent systemic illness despite antibacterial therapy

• ●

Evidence of invasive fungal infection

→ Consider an opportunistic mold or yeast-like fungus, including Geotrichum candidum

Diagnosis

Diagnosis is based on:

Identification of the fungus in tissue biopsy

and

Fungal culture

Demonstration of fungal invasion within tissue is particularly valuable because Geotrichum may occasionally represent colonization rather than invasive disease.

Histopathology

Tissue examination may demonstrate:

Hyaline septate hyphae

with

Arthroconidia

This appearance should prompt consideration of an arthroconidial fungus.

Culture

Culture allows the organism to be isolated and identified.

Because several fungi can produce arthroconidia, accurate laboratory identification is important for distinguishing Geotrichum from other morphologically similar fungi.

Important Differential Diagnosis

Arthroconidia may also be encountered with other fungi, making differentiation important.

For example:

Geotrichum

→ Hyaline septate hyphae with arthroconidia

Coccidioides

→ Produces arthroconidia environmentally, but spherules containing endospores are the characteristic tissue form

Thus:

Arthroconidia seen in tissue

→ favors an organism such as Geotrichum rather than Coccidioides.

Treatment

The source emphasizes that there are limited clinical data regarding optimal antifungal therapy for G. candidum infection.

It describes:

Intravenous amphotericin B

as having been used with moderate success.

Treatment Considerations

Because invasive geotrichosis is uncommon, management should take into account:

• Severity and extent of infection

• Antifungal susceptibility when available

• Underlying immune status

• Degree and duration of neutropenia

• Potential need for source control

Treatment of invasive disease should be individualized.

Importance of Immune Recovery

As with many opportunistic mold infections, improvement in host immune function can be extremely important.

In neutropenic patients:

Antifungal therapy

• ●

Recovery from neutropenia

→ improves the likelihood of controlling invasive fungal infection.

Persistent profound neutropenia can make disseminated disease particularly difficult to treat.

High-Yield Clinical Pattern

Profoundly neutropenic patient

• ●

Disseminated fungal infection

• ●

Tissue biopsy showing septate hyaline hyphae with arthroconidia

→ Think Geotrichum candidum

Exam Essentials

Organism: Geotrichum candidum

Disease: Geotrichosis

Type: Filamentous fungus / mold-like fungus

Hyphae: Septate and hyaline

Characteristic structure: Arthroconidia

Distribution: Worldwide

Frequency: Rare

Major risk factor: Neutropenia

Major severe manifestation: Disseminated infection

Diagnosis: Tissue biopsy + fungal culture

Tissue morphology: Septate hyaline hyphae with arthroconidia

Treatment in source: IV amphotericin B

Evidence base: Limited

Important management factor: Recovery of immune function/neutrophils

Key clinical pearl: Geotrichum candidum is a rare opportunistic fungus characterized by septate hyaline hyphae and arthroconidia in tissue. The classic severe presentation is disseminated infection in a profoundly neutropenic patient.

Medicine – Benign Essential Tremor

Essential tremor is a common movement disorder characterised primarily by an action tremor, meaning the tremor appears during voluntary movement or while maintaining a posture against gravity. It is usually bilateral and most often affects the hands and forearms, but the head and voice may also be involved.

The older term “benign essential tremor” is still encountered, but essential tremor is preferred because the condition can sometimes cause significant functional disability.

1. Tremor with Movement

The tremor of essential tremor is typically an action or postural tremor.

It is most noticeable when the patient:

Holds the arms outstretched.

Writes.

Uses cutlery.

Drinks from a cup.

Performs other fine hand movements.

A classic resting tremor is not the dominant feature.

2. Difference from Parkinson Tremor

Essential tremor is easiest to distinguish from Parkinson disease by the timing of the tremor.

Essential tremor → tremor mainly with posture or movement.

Parkinson disease → tremor classically occurs at rest.

Parkinson tremor is also often initially asymmetric and accompanied by bradykinesia and rigidity, whereas essential tremor usually lacks these Parkinsonian features.

3. Distribution

The hands and arms are most commonly affected.

The tremor may also involve:

Head.

Voice.

Less commonly, other body regions may be involved.

Head tremor may appear as repeated “yes-yes” or “no-no” movements.

4. Bilateral Tremor

Essential tremor is typically bilateral, although one side may initially be more noticeable than the other.

This differs from Parkinson disease, which often begins clearly asymmetrically.

5. Inheritance

Essential tremor often has a strong familial component.

Many families show an autosomal dominant pattern of inheritance, although the genetics are heterogeneous and not every patient has an affected relative.

Therefore, a positive family history supports the diagnosis but is not required.

6. Effect of Stress

The tremor commonly becomes worse with:

Anxiety.

Emotional stress.

Fatigue.

Sleep deprivation.

Stimulants such as excess caffeine.

Patients may therefore notice substantial day-to-day variation in severity.

7. Effect of Alcohol

A characteristic historical feature is temporary improvement after a small amount of alcohol.

This can be a useful diagnostic clue.

However, alcohol should not be recommended as a treatment because of tolerance, dependence, rebound worsening, and other health risks.

8. Neurological Examination

In otherwise typical essential tremor, the remainder of the neurological examination is generally normal.

There should not be prominent:

Bradykinesia.

Rigidity.

Cerebellar signs.

Focal neurological deficits.

The presence of these findings suggests another diagnosis.

9. Diagnosis

Essential tremor is primarily a clinical diagnosis.

The history and examination should establish a persistent bilateral upper-limb action tremor and exclude more likely alternative causes.

Investigations are usually directed toward excluding secondary causes when the presentation is atypical.

10. Secondary Causes to Exclude

Other causes of tremor include:

Hyperthyroidism.

Drug-induced tremor.

Excess caffeine or stimulants.

Alcohol withdrawal.

Parkinson disease.

Cerebellar disorders.

Dystonic tremor.

Therefore, the diagnosis should not be made solely because the tremor improves with alcohol.

11. Propranolol

Propranolol, a non-selective beta-blocker, is a major first-line treatment when the tremor causes functional impairment.

It can reduce tremor amplitude and improve tasks such as writing, eating, and drinking.

The old statement that only about 30% respond is too restrictive; response rates vary, and many patients obtain at least partial benefit.

12. Primidone

Another important first-line treatment is primidone.

Primidone is an anticonvulsant that can significantly reduce essential tremor and is often used when propranolol is ineffective, contraindicated, or not tolerated.

Therefore, the main medications to remember are:

Propranolol.

Primidone.

13. When Propranolol May Be Unsuitable

Because propranolol blocks beta receptors, it may be unsuitable in some patients, particularly those with:

Asthma.

Marked bradycardia.

Certain conduction abnormalities.

Treatment therefore needs to be individualised.

14. Other Treatment Options

If first-line treatment is inadequate, specialist management may include other medications or procedural treatments.

For severe disabling medication-resistant tremor, options may include:

Deep brain stimulation.

Focused ultrasound thalamotomy in selected patients.

These are generally reserved for significant refractory disease.

15. Essential Tremor – Note Form

Type of tremor: action/postural tremor.

Rest tremor: not the classic dominant feature.

Distribution: mainly hands and arms; head and voice may also be affected.

Inheritance: often autosomal dominant.

Stress: worsens tremor.

Alcohol: may temporarily improve tremor but is not a recommended treatment.

Neurological examination: otherwise usually normal.

First-line treatment: propranolol or primidone when symptoms are functionally troublesome.

Key Clinical Pattern

Remember essential tremor as:

Bilateral action tremor + hands/head involvement + worse with stress + may improve transiently with alcohol.

The easiest distinction is:

Essential tremor → action/postural tremor.

Parkinson disease → resting tremor + bradykinesia + rigidity.

And the key treatment pair is:

Propranolol or primidone.

1. Tremor with Movement The tremor of essential tremor is typically an action or postural tremor. It is most noticeable when the patient: Holds the arms outstretched. Writes. Uses cutlery. Drinks from a cup. Performs other fine hand movements. A classic resting tremor is not the dominant feature. 

2. Difference from Parkinson Tremor Essential tremor is easiest to distinguish from Parkinson disease by the timing of the tremor. Essential tremor → tremor mainly with posture or movement. Parkinson disease → tremor classically occurs at rest. Parkinson tremor is also often initially asymmetric and accompanied by bradykinesia and rigidity, whereas essential tremor usually lacks these Parkinsonian features. 

3. Distribution The hands and arms are most commonly affected. The tremor may also involve: Head. Voice. Less commonly, other body regions may be involved. Head tremor may appear as repeated “yes-yes” or “no-no” movements. 

4. Bilateral Tremor Essential tremor is typically bilateral, although one side may initially be more noticeable than the other. This differs from Parkinson disease, which often begins clearly asymmetrically. 

5. Inheritance Essential tremor often has a strong familial component. Many families show an autosomal dominant pattern of inheritance, although the genetics are heterogeneous and not every patient has an affected relative. Therefore, a positive family history supports the diagnosis but is not required. 

6. Effect of Stress The tremor commonly becomes worse with: Anxiety. Emotional stress. Fatigue. Sleep deprivation. Stimulants such as excess caffeine. Patients may therefore notice substantial day-to-day variation in severity. 

7. Effect of Alcohol A characteristic historical feature is temporary improvement after a small amount of alcohol. This can be a useful diagnostic clue. However, alcohol should not be recommended as a treatment because of tolerance, dependence, rebound worsening, and other health risks. 

8. Neurological Examination In otherwise typical essential tremor, the remainder of the neurological examination is generally normal. There should not be prominent: Bradykinesia. Rigidity. Cerebellar signs. Focal neurological deficits. The presence of these findings suggests another diagnosis. 

9. Diagnosis Essential tremor is primarily a clinical diagnosis. The history and examination should establish a persistent bilateral upper-limb action tremor and exclude more likely alternative causes. Investigations are usually directed toward excluding secondary causes when the presentation is atypical. 

10. Secondary Causes to Exclude Other causes of tremor include: Hyperthyroidism. Drug-induced tremor. Excess caffeine or stimulants. Alcohol withdrawal. Parkinson disease. Cerebellar disorders. Dystonic tremor. Therefore, the diagnosis should not be made solely because the tremor improves with alcohol. 

11. Propranolol Propranolol, a non-selective beta-blocker, is a major first-line treatment when the tremor causes functional impairment. It can reduce tremor amplitude and improve tasks such as writing, eating, and drinking. The old statement that only about 30% respond is too restrictive; response rates vary, and many patients obtain at least partial benefit. 

12. Primidone Another important first-line treatment is primidone. Primidone is an anticonvulsant that can significantly reduce essential tremor and is often used when propranolol is ineffective, contraindicated, or not tolerated. Therefore, the main medications to remember are: Propranolol. Primidone. 

13. When Propranolol May Be Unsuitable Because propranolol blocks beta receptors, it may be unsuitable in some patients, particularly those with: Asthma. Marked bradycardia. Certain conduction abnormalities. Treatment therefore needs to be individualised. 

14. Other Treatment Options If first-line treatment is inadequate, specialist management may include other medications or procedural treatments. For severe disabling medication-resistant tremor, options may include: Deep brain stimulation. Focused ultrasound thalamotomy in selected patients. These are generally reserved for significant refractory disease. 

15. Essential Tremor – Note Form Type of tremor: action/postural tremor. 

Rest tremor: not the classic dominant feature. 

Distribution: mainly hands and arms; head and voice may also be affected. 

Inheritance: often autosomal dominant. 

Stress: worsens tremor. 

Alcohol: may temporarily improve tremor but is not a recommended treatment. 

Neurological examination: otherwise usually normal. 

First-line treatment: propranolol or primidone when symptoms are functionally troublesome. 

Key Clinical Pattern Remember essential tremor as: Bilateral action tremor + hands/head involvement + worse with stress + may improve transiently with alcohol. The easiest distinction is: Essential tremor → action/postural tremor. Parkinson disease → resting tremor + bradykinesia + rigidity. And the key treatment pair is: Propranolol or primidone.

Medicine – Huntington Disease

Huntington disease (HD) is a progressive autosomal dominant neurodegenerative disorder characterised by a combination of chorea, psychiatric disturbance, and progressive cognitive decline. Symptoms most commonly begin in adult life, often between about 30 and 50 years of age, although onset can occur earlier or later.

Because the disorder is autosomal dominant, an affected person usually has an affected parent, although the family history may occasionally appear negative because of early parental death, unrecognised disease, or a new mutation.

1. Inheritance

Huntington disease is inherited in an autosomal dominant pattern.

This means that an affected individual has a 50% chance of transmitting the pathogenic variant to each child, regardless of the child’s sex.

Both males and females can therefore be affected and can transmit the disease.

2. Genetic Defect

Huntington disease is caused by expansion of a CAG trinucleotide repeat in the HTT gene on chromosome 4.

The CAG sequence codes for glutamine, so the mutation produces an abnormally long polyglutamine tract in the huntingtin protein.

The abnormal protein ultimately causes progressive neuronal dysfunction and death.

3. Anticipation

Huntington disease demonstrates anticipation.

This means that the disease can present at an earlier age in successive generations when the CAG repeat expands further.

Anticipation is particularly associated with paternal transmission, because repeat expansion is more likely during spermatogenesis.

Therefore:

More CAG repeats → generally earlier disease onset.

4. Neuropathology

The most characteristic pathological changes involve degeneration of neurons within the striatum, especially the:

Caudate nucleus.

Putamen.

Loss of striatal neurons disrupts the normal basal-ganglia control of movement and contributes to chorea and other motor abnormalities.

5. Caudate Atrophy

As the disease progresses, marked caudate nucleus atrophy may develop.

On brain imaging this can produce enlargement of the frontal horns of the lateral ventricles.

This is a classic structural feature of advanced Huntington disease.

6. Age of Onset

Symptoms classically begin between approximately 30 and 50 years of age.

However, there is considerable variation.

Some patients develop disease later in life, while those with very large CAG expansions can present much earlier.

7. Juvenile Huntington Disease

Disease beginning before about 20 years of age is called juvenile Huntington disease.

Unlike classic adult Huntington disease, juvenile cases may show more:

Rigidity.

Bradykinesia.

Dystonia.

Seizures.

Chorea may actually be less prominent.

This juvenile phenotype is sometimes called the Westphal variant.

8. Chorea

Chorea is the characteristic movement disorder of classic Huntington disease.

It consists of involuntary, irregular, unpredictable, flowing movements that seem to move randomly from one part of the body to another.

The movements are not rhythmic.

They may affect the:

Face.

Arms.

Legs.

Trunk.

9. Appearance of Chorea

Early chorea may initially look like normal restlessness or fidgeting.

Patients may incorporate involuntary movements into apparently purposeful actions, sometimes making them difficult to recognise initially.

As disease progresses, the movements become more obvious and may interfere with walking, speech, eating, and daily activities.

10. Other Motor Features

Huntington disease is not limited to chorea.

Patients may also develop:

Dystonia.

Abnormal eye movements.

Dysarthria.

Dysphagia.

Impaired gait and balance.

In advanced disease, chorea may become less prominent while rigidity and bradykinesia increase.

11. Cognitive Decline

Progressive cognitive impairment is a central component of Huntington disease.

Early abnormalities commonly involve executive function, including difficulty with:

Planning.

Organisation.

Problem solving.

Attention.

Mental flexibility.

As the disease progresses, cognitive impairment may eventually develop into dementia.

12. Dementia

Dementia usually develops gradually as neurodegeneration progresses.

Unlike Alzheimer’s disease, early problems may be dominated by executive dysfunction and slowed thinking rather than severe early loss of episodic memory.

Eventually, multiple cognitive domains become affected.

13. Psychiatric Features

Psychiatric symptoms are extremely important and may precede the obvious movement disorder.

These can include:

Depression.

Irritability.

Anxiety.

Apathy.

Impulsivity.

Obsessive or compulsive behaviour.

Psychosis in some patients.

Therefore, Huntington disease should be considered a motor, cognitive, and psychiatric disorder.

14. Family History

A positive family history strongly supports the diagnosis because Huntington disease is autosomal dominant.

A typical history may reveal a parent or grandparent who developed unusual movements, personality changes, psychiatric illness, or progressive dementia during adulthood.

However, an apparently negative family history does not completely exclude the disease.

15. Genetic Testing

The diagnosis can be confirmed by molecular genetic testing demonstrating an expanded CAG repeat in the HTT gene.

Testing an individual who already has compatible symptoms is called diagnostic genetic testing.

16. Predictive Genetic Testing

Because Huntington disease usually develops in adulthood, an asymptomatic adult with an affected parent may request predictive testing.

This is a major decision because a positive result predicts a high likelihood of future disease before symptoms appear.

Predictive testing therefore requires careful genetic counselling, informed consent, and psychological support.

17. Treatment Principles

There is currently no treatment that reliably reverses the underlying neurodegeneration.

Management therefore focuses on:

Controlling abnormal movements.

Treating psychiatric symptoms.

Maintaining nutrition and swallowing safety.

Physiotherapy and mobility support.

Speech and language therapy.

Genetic counselling.

Psychological and social support.

18. Treatment of Chorea

The older note lists chlorpromazine to relieve chorea.

Dopamine-blocking antipsychotic drugs can indeed reduce choreiform movements, particularly when the patient also has behavioural disturbance or psychosis.

However, chlorpromazine is not generally regarded as the principal modern treatment specifically for Huntington chorea.

19. Tetrabenazine

Tetrabenazine is an important treatment for troublesome Huntington-related chorea.

It inhibits vesicular monoamine transporter type 2 (VMAT2), reducing storage and release of monoamines such as dopamine.

The resulting reduction in dopaminergic activity helps suppress choreiform movements.

20. Deutetrabenazine

Deutetrabenazine is a related VMAT2 inhibitor that may also be used to treat Huntington chorea.

Drug selection depends on availability, individual symptoms, adverse-effect risk, and specialist assessment.

21. Antipsychotic Drugs

Antipsychotic drugs may be especially useful when chorea occurs together with:

Psychosis.

Severe agitation.

Aggressive behaviour.

Some atypical antipsychotics are often preferred over older drugs such as chlorpromazine because treatment can be tailored according to adverse effects and psychiatric symptoms.

22. Depression and Suicide Risk

Depression is common in Huntington disease and requires active treatment.

Patients can also have an increased risk of suicidal thoughts and behaviour, particularly around diagnosis and during periods of declining function.

Psychiatric assessment and ongoing support are therefore essential components of care.

23. Dysphagia and Nutrition

Progressive motor dysfunction may cause dysphagia.

At the same time, continuous involuntary movements can increase energy expenditure.

Patients may consequently develop significant weight loss and nutritional problems.

Swallowing assessment and nutritional support become increasingly important as disease advances.

24. Huntington Disease – Note Form

Inheritance: autosomal dominant.

Gene: HTT gene on chromosome 4.

Mutation: CAG trinucleotide repeat expansion.

Anticipation: increasing CAG repeat length can cause earlier onset in later generations, particularly with paternal transmission.

Typical onset: approximately 30–50 years, although highly variable.

Main movement disorder: chorea.

Chorea: irregular, involuntary, non-rhythmic flowing movements.

Cognition: progressive executive dysfunction followed by dementia.

Psychiatric features: depression, irritability, apathy, behavioural disturbance and sometimes psychosis.

Family history: usually positive because of autosomal dominant inheritance.

Pathology: degeneration of the caudate and putamen.

Imaging: caudate atrophy may lead to enlargement of the frontal horns of the lateral ventricles.

Diagnosis: genetic demonstration of expanded CAG repeats in HTT.

Treatment of chorea: VMAT2 inhibitors such as tetrabenazine or deutetrabenazine are important modern options.

Antipsychotics: may reduce chorea and are particularly useful when psychiatric or behavioural symptoms coexist.

Chlorpromazine: can suppress chorea but is an older treatment and is not usually the main modern first-choice drug specifically for chorea.

Key Clinical Pattern

Remember Huntington disease as:

Autosomal dominant + adult onset + chorea + psychiatric disturbance + progressive dementia.

The genetic mechanism is:

Chromosome 4 HTT gene → CAG repeat expansion → abnormal huntingtin protein → striatal neurodegeneration.

The classic pathological structure is:

Caudate nucleus atrophy.

And the major treatment update is:

Troublesome chorea → think VMAT2 inhibition, especially tetrabenazine or deutetrabenazine, rather than chlorpromazine alone.

Medicine – Parkinsonism

Parkinsonism is a clinical syndrome characterised mainly by bradykinesia together with rigidity and/or resting tremor, usually caused by impaired dopaminergic function within the nigrostriatal pathway of the basal ganglia.

The commonest cause is idiopathic Parkinson disease, but several drugs, toxins, neurodegenerative disorders, and structural neurological conditions can produce a similar syndrome.

1. Dopamine Deficiency

In Parkinson disease, there is progressive degeneration of dopaminergic neurons in the substantia nigra pars compacta.

These neurons normally project to the striatum, particularly the caudate nucleus and putamen.

Loss of these neurons causes:

Reduced dopamine in the nigrostriatal pathway → impaired basal ganglia motor control → bradykinesia, rigidity and tremor.

So the important site is not simply “dopamine deficiency in the substantia nigra,” but rather loss of substantia nigra neurons causing reduced dopamine delivery to the striatum.

2. Lewy Bodies

A classic pathological feature of idiopathic Parkinson disease is the presence of Lewy bodies within affected neurons.

Lewy bodies are intracellular inclusions composed largely of abnormal aggregates of alpha-synuclein.

They are particularly associated with degeneration in the substantia nigra but can also be found in other regions of the nervous system.

3. Core Motor Features

The classic motor syndrome consists of:

Bradykinesia.

Rigidity.

Resting tremor.

Postural instability may occur later in the disease.

Modern diagnostic approaches generally require bradykinesia as a central feature of parkinsonism.

4. Resting Tremor

The typical Parkinson tremor occurs mainly at rest.

It often begins asymmetrically in one hand and may resemble the repetitive movement of rolling a small object between the thumb and fingers.

This is the classic pill-rolling tremor.

5. Characteristics of Parkinson Tremor

Typical features include:

Resting tremor.

Usually asymmetric at onset.

Frequency commonly around 4–6 Hz.

Reduced during voluntary movement.

Disappears during sleep.

The older figure of 3–5 Hz is close, but 4–6 Hz is a commonly used modern description.

Stress or emotional tension may make the tremor more obvious.

6. Bradykinesia

Bradykinesia means slowness of movement and is one of the most important features of Parkinsonism.

Patients may have difficulty initiating movement and may progressively reduce the speed and amplitude of repetitive movements.

Examples include:

Slow walking.

Difficulty turning in bed.

Reduced spontaneous movement.

Slow dressing and eating.

Difficulty starting to walk.

7. Hypokinesia and Akinesia

Bradykinesia is often accompanied by:

Hypokinesia – reduced amplitude of movement.

Akinesia – difficulty initiating movement or episodes of temporary inability to move.

These features contribute to freezing and gait difficulty in more advanced disease.

8. Rigidity

Rigidity is increased resistance to passive movement of a limb.

Unlike spasticity, Parkinsonian rigidity is not strongly dependent on the speed of movement.

Two classic patterns are described.

9. Lead-Pipe Rigidity

Lead-pipe rigidity produces smooth, sustained resistance throughout the range of passive movement.

The examiner feels continuous stiffness when moving the patient’s limb.

10. Cogwheel Rigidity

Cogwheel rigidity produces a ratchet-like or jerky resistance during passive movement.

It is thought to result from rigidity combined with an underlying tremor.

This is particularly characteristic of Parkinsonism.

11. Expressionless Face

Patients may develop reduced spontaneous facial movement, producing a relatively expressionless or mask-like face.

This is called hypomimia.

Blinking may also become less frequent.

12. Speech Changes

Speech may become:

Quiet.

Monotonous.

Rapid or indistinct.

Reduced voice volume is called hypophonia.

Patients may also have difficulty articulating clearly as the disease progresses.

13. Festinant and Shuffling Gait

Parkinsonian gait is typically short-stepped and shuffling.

Patients may walk with:

Reduced arm swing.

Stooped posture.

Short steps.

Difficulty initiating gait.

Difficulty turning.

14. Festination

Festination refers to progressively faster, shorter steps as the patient appears to chase the body’s centre of gravity.

The patient may lean forward and seem unable to stop easily.

Therefore, festination is related to but not exactly identical to a simple shuffling gait.

15. Freezing of Gait

Patients may experience freezing, particularly when:

Starting to walk.

Turning.

Passing through narrow doorways.

Approaching obstacles.

The feet may appear temporarily “stuck to the floor.”

16. Reduced Arm Swing

Loss of normal arm swing during walking is an early and useful clue.

It may be more marked on one side, reflecting the typical asymmetrical onset of Parkinson disease.

17. Micrographia

Micrographia means progressively small handwriting.

As the patient continues writing, the letters may become smaller and more cramped.

It reflects bradykinesia and reduced amplitude of repetitive movement.

18. Dysphagia

Difficulty swallowing may develop because of impaired coordination and bradykinesia of the bulbar muscles.

Dysphagia can lead to:

Choking.

Weight loss.

Aspiration.

Aspiration pneumonia.

It becomes particularly important in more advanced disease.

19. Postural Instability

Postural reflexes may become impaired later in Parkinson disease.

This can cause:

Poor balance.

Falls.

Difficulty recovering after being pushed.

Early severe postural instability should raise suspicion for an atypical Parkinsonian disorder rather than uncomplicated idiopathic Parkinson disease.

20. Autonomic Dysfunction

Autonomic symptoms are common.

These can include:

Postural hypotension.

Constipation.

Urinary dysfunction.

Sexual dysfunction.

Excessive sweating.

Orthostatic hypotension may result from the disease itself or be worsened by dopaminergic medication.

21. Depression

Depression is common in Parkinson disease and may occur before or after motor symptoms begin.

The old figure of about 30% is a reasonable historical approximation, but prevalence varies depending on definitions and patient population.

Depression should be regarded as an important non-motor manifestation, not merely a psychological reaction to disability.

22. Other Non-Motor Features

Parkinson disease is a multisystem disorder.

Other important non-motor symptoms include:

Anosmia or hyposmia.

REM sleep behaviour disorder.

Constipation.

Fatigue.

Anxiety.

Cognitive impairment.

Hallucinations.

Sleep disturbance.

Some of these can precede the motor syndrome by years.

23. Idiopathic Parkinson Disease

Idiopathic Parkinson disease is the commonest cause of Parkinsonism.

It typically begins asymmetrically and progresses gradually.

A good clinical response to levodopa supports the diagnosis.

24. Drug-Induced Parkinsonism

A common secondary cause is drug-induced Parkinsonism, particularly from medications that block dopamine receptors.

Important examples include some:

Antipsychotic drugs.

Antiemetic dopamine antagonists.

Examples include metoclopramide and prochlorperazine.

Drug-induced Parkinsonism is often more symmetrical than idiopathic Parkinson disease.

25. Dementia Pugilistica

The older term dementia pugilistica refers to neurological damage associated with repeated head trauma, historically described in boxers.

The broader modern concept is chronic traumatic encephalopathy (CTE).

Repeated head injury can produce cognitive, behavioural, and motor abnormalities, including Parkinsonian features in some patients.

26. Post-Encephalitic Parkinsonism

Parkinsonism can occur after encephalitic illness.

Historically, this was particularly associated with encephalitis lethargica, although this is now rare.

Damage to basal ganglia structures can lead to persistent Parkinsonian symptoms.

27. Normal-Pressure Hydrocephalus

Normal-pressure hydrocephalus (NPH) can produce a gait disorder that may resemble Parkinsonism.

The classic triad is:

Gait disturbance.

Cognitive impairment.

Urinary incontinence.

The gait is often broad-based, short-stepped, and described as “magnetic.”

Prominent resting tremor is less typical than in idiopathic Parkinson disease.

28. Toxin-Induced Parkinsonism

Several toxins can damage dopaminergic pathways and produce Parkinsonism.

Important examples include:

MPTP.

Carbon monoxide.

Manganese.

Some other toxic exposures may also contribute depending on dose and duration.

29. MPTP

MPTP is a neurotoxin that selectively damages dopaminergic neurons in the substantia nigra.

It produces a syndrome that can closely resemble idiopathic Parkinson disease.

Its discovery played an important role in understanding Parkinson disease pathophysiology.

30. Carbon Monoxide

Severe carbon monoxide poisoning can damage the basal ganglia, particularly the globus pallidus.

Delayed neurological complications may include:

Parkinsonism.

Cognitive impairment.

Movement disorders.

31. Manganese

Chronic manganese exposure can cause a Parkinsonian syndrome.

However, the pattern may differ somewhat from idiopathic Parkinson disease, with more prominent gait and postural abnormalities and less classic resting tremor.

32. Narcotics

The original note lists “narcotics” as a cause.

This is too broad.

Most opioids do not directly cause classical chronic Parkinsonism.

The historically important association is with MPTP contamination in illicit drug exposure, which can produce profound Parkinsonism.

Therefore, it is better to remember MPTP specifically rather than “narcotics” in general.

33. Wilson Disease

Wilson disease is an important cause of Parkinsonian symptoms in younger patients.

It results from abnormal copper metabolism due to mutations in ATP7B.

Neurological features may include:

Tremor.

Rigidity.

Dystonia.

Dysarthria.

Parkinsonism.

The presence of Kayser–Fleischer rings and liver disease can provide important clues.

34. Other Atypical Parkinsonian Disorders

Not every patient with Parkinsonism has idiopathic Parkinson disease.

Important atypical neurodegenerative causes include:

Multiple system atrophy.

Progressive supranuclear palsy.

Corticobasal syndrome.

Dementia with Lewy bodies.

These conditions often respond less well to levodopa and may have additional early neurological features.

35. Multiple System Atrophy

Multiple system atrophy (MSA) combines Parkinsonism with prominent autonomic dysfunction and sometimes cerebellar or pyramidal signs.

Early severe postural hypotension, urinary dysfunction, and poor levodopa response may suggest MSA.

36. Progressive Supranuclear Palsy

Progressive supranuclear palsy (PSP) can cause:

Parkinsonism.

Early falls.

Axial rigidity.

Vertical gaze palsy.

The levodopa response is usually limited.

37. Dementia with Lewy Bodies

Dementia with Lewy bodies may cause Parkinsonism together with:

Early cognitive impairment.

Fluctuating cognition.

Visual hallucinations.

REM sleep behaviour disorder.

When dementia occurs before or within about a year of Parkinsonism, dementia with Lewy bodies is generally considered rather than Parkinson disease dementia.

38. Diagnosis

Parkinson disease is primarily a clinical diagnosis.

There is no single routine blood test that confirms it.

Diagnosis is based on the pattern of bradykinesia, rigidity, tremor, asymmetry, progression, response to levodopa, and absence of features strongly suggesting another disorder.

39. Imaging

Routine brain imaging is not always required to diagnose typical Parkinson disease.

MRI may be useful when the presentation is atypical or when another structural cause needs to be excluded.

Specialised dopamine-transporter imaging can sometimes help distinguish degenerative Parkinsonism from disorders such as essential tremor, but it does not by itself distinguish all Parkinsonian syndromes.

40. Drug Treatment

Drug treatment aims to improve motor symptoms by increasing dopaminergic activity or reducing relative cholinergic activity within the basal ganglia.

The major drug groups include:

Levodopa combined with carbidopa or benserazide.

Dopamine agonists.

MAO-B inhibitors.

COMT inhibitors.

Anticholinergic drugs in selected patients.

41. Levodopa

Levodopa remains the most effective symptomatic treatment for Parkinson motor symptoms.

It is usually combined with carbidopa or benserazide, which reduce peripheral conversion of levodopa into dopamine.

Levodopa is particularly effective for:

Bradykinesia.

Rigidity.

It also frequently improves tremor.

42. Dopamine Agonists

Dopamine agonists include:

Pramipexole.

Ropinirole.

Rotigotine.

Apomorphine in selected advanced disease.

They directly stimulate dopamine receptors and may be used alone or in combination with levodopa.

43. MAO-B Inhibitors

Examples include:

Selegiline.

Rasagiline.

Safinamide.

They inhibit dopamine breakdown and can provide symptomatic benefit or reduce “off” time when used with levodopa.

44. COMT Inhibitors

Examples include:

Entacapone.

Opicapone.

They prolong the effect of levodopa and are particularly useful for end-of-dose wearing-off.

45. Anticholinergic Drugs

Examples include:

Procyclidine.

Benztropine.

They mainly reduce tremor and are sometimes particularly useful in drug-induced Parkinsonism.

Because they can cause confusion, urinary retention, constipation, and blurred vision, they are generally used cautiously, especially in older patients.

46. Non-Drug Management

Management should not rely only on medication.

Important supportive measures include:

Physiotherapy.

Occupational therapy.

Speech and language therapy.

Swallowing assessment.

Exercise programmes.

Falls prevention.

Management of depression, sleep problems, constipation, and autonomic symptoms.

47. Advanced Treatment

Selected patients with advanced Parkinson disease and motor fluctuations despite optimal medication may be considered for treatments such as:

Deep brain stimulation.

Continuous apomorphine infusion.

Continuous levodopa-based infusion therapies.

These require specialist assessment.

48. Parkinsonism – Note Form

Pathology in Parkinson disease: degeneration of dopaminergic neurons in substantia nigra pars compacta.

Result: reduced dopamine in the striatum.

Pathological hallmark: Lewy bodies containing alpha-synuclein.

Core feature: bradykinesia.

Resting tremor: pill-rolling, usually asymmetric, around 4–6 Hz, reduced with movement and absent during sleep.

Rigidity: lead-pipe or cogwheel.

Face: hypomimia or mask-like expression.

Gait: short, shuffling steps with reduced arm swing; festination and freezing may occur.

Writing: micrographia.

Swallowing: dysphagia may occur.

Autonomic symptoms: postural hypotension, constipation and urinary dysfunction.

Psychiatric feature: depression is common.

Idiopathic cause: Parkinson disease.

Drug-induced: dopamine receptor antagonists, especially antipsychotics and some antiemetics.

Trauma: chronic repetitive head injury may cause Parkinsonian features.

NPH: gait disturbance + cognitive decline + urinary incontinence.

Toxins: MPTP, carbon monoxide and manganese.

Young patient: consider Wilson disease.

Treatment: levodopa, dopamine agonists, MAO-B inhibitors, COMT inhibitors and selected anticholinergics.

Key Clinical Pattern

Remember Parkinsonism as:

Bradykinesia + resting tremor + rigidity.

The classic patient has:

Asymmetric pill-rolling resting tremor.

Cogwheel rigidity.

Slow movements.

Reduced facial expression.

Micrographia.

Shuffling gait with reduced arm swing.

The underlying mechanism in idiopathic Parkinson disease is:

Substantia nigra degeneration → ↓ striatal dopamine → impaired basal ganglia motor control.

And the major secondary causes to remember are:

Dopamine-blocking drugs + NPH + toxins + Wilson disease + atypical neurodegenerative disorders.

Medicine – Drugs Used in Parkinsonism

Drug treatment of Parkinson disease aims mainly to restore the imbalance between dopaminergic and cholinergic activity within the basal ganglia. The major motor manifestations—bradykinesia, rigidity, resting tremor, and later postural instability—result largely from degeneration of dopaminergic neurons in the substantia nigra pars compacta, causing reduced dopamine within the striatum.

The drugs in your table can be organised into five important groups: levodopa, dopamine agonists, MAO-B inhibitors, COMT inhibitors, and anticholinergic drugs. Some details in the older table need updating because modern Parkinson treatment has changed considerably.

1. Levodopa

Levodopa (L-DOPA) is the metabolic precursor of dopamine and remains the most effective symptomatic treatment for the motor features of Parkinson disease, particularly bradykinesia and rigidity.

Dopamine itself cannot effectively cross the blood–brain barrier. Levodopa, however, can cross into the CNS and is then converted into dopamine by DOPA decarboxylase.

Therefore:

Levodopa crosses blood–brain barrier → converted to dopamine in brain → replenishes striatal dopamine → improves Parkinsonian motor symptoms.

2. Levodopa with Carbidopa or Benserazide

Levodopa is almost always given with a peripheral DOPA-decarboxylase inhibitor, such as:

Carbidopa.

Benserazide.

These drugs inhibit the peripheral conversion of levodopa into dopamine but do not significantly cross the blood–brain barrier.

Consequently, more levodopa reaches the CNS and peripheral dopaminergic adverse effects are reduced.

3. Why Levodopa Is Not Given Alone

If levodopa were given alone, a substantial amount would be converted into dopamine in peripheral tissues before reaching the brain.

Peripheral dopamine can cause adverse effects such as:

Nausea and vomiting.

Postural hypotension.

Cardiovascular effects.

Adding carbidopa or benserazide therefore both increases CNS availability of levodopa and reduces peripheral adverse effects.

4. Effects of Levodopa

Levodopa is particularly effective at improving:

Bradykinesia.

Rigidity.

It also improves tremor in many patients.

Its effect on later problems such as postural instability, freezing, speech disturbance, and some non-motor manifestations may be less predictable.

5. Motor Fluctuations with Levodopa

After prolonged treatment, patients may develop motor fluctuations.

One important pattern is wearing-off, in which the effect of each levodopa dose becomes progressively shorter.

The patient improves after taking a dose but develops recurrent Parkinsonian symptoms before the next dose is due.

This is sometimes called end-of-dose deterioration.

6. On–Off Phenomenon

Patients receiving long-term levodopa may also experience an on–off phenomenon.

During an “on” period, mobility is relatively good and the medication is working effectively.

During an “off” period, Parkinsonian symptoms suddenly become much more prominent, with severe bradykinesia or inability to move.

These fluctuations can become unpredictable in advanced disease.

7. Levodopa-Induced Dyskinesia

Long-term levodopa therapy can produce dyskinesias, meaning involuntary abnormal movements.

These are often choreiform or writhing movements and commonly occur when levodopa concentrations are relatively high.

Thus:

Long-term levodopa → motor fluctuations + dyskinesias.

8. Neuropsychiatric Effects of Levodopa

Dopaminergic treatment may cause neuropsychiatric complications, particularly in older or cognitively vulnerable patients.

These can include:

Hallucinations.

Confusion.

Vivid dreams.

Psychotic symptoms.

Hallucinations are therefore an important adverse effect to remember.

9. Dopamine Agonists

Dopamine agonists directly stimulate dopamine receptors and therefore do not require conversion into dopamine.

The older table lists:

Bromocriptine.

Pergolide.

These are older ergot-derived dopamine agonists and are now much less commonly used for Parkinson disease because of their adverse-effect profiles.

10. Modern Dopamine Agonists

More commonly encountered modern dopamine agonists include:

Pramipexole.

Ropinirole.

Rotigotine.

Apomorphine is another dopamine agonist used in selected patients, particularly for troublesome “off” episodes or advanced disease.

11. Mechanism of Dopamine Agonists

Dopamine agonists directly stimulate dopamine receptors in the basal ganglia.

Many have substantial activity at the D₂-family of dopamine receptors.

They can improve:

Bradykinesia.

Rigidity.

Tremor.

They may be used alone in selected patients or together with levodopa.

12. Advantages of Dopamine Agonists

Dopamine agonists have longer pharmacological effects than levodopa and can sometimes reduce “off” time when added to levodopa.

However, they are generally less effective than levodopa for overall motor symptom control and often produce more troublesome neuropsychiatric and behavioural adverse effects.

13. Adverse Effects of Dopamine Agonists

Important adverse effects include:

Nausea.

Postural hypotension.

Hallucinations.

Confusion.

Somnolence and sudden sleep attacks.

Peripheral oedema.

14. Impulse-Control Disorders

An especially important adverse effect of dopamine agonists is the development of impulse-control disorders.

These may include:

Pathological gambling.

Compulsive shopping.

Binge eating.

Hypersexuality.

Patients and families should therefore be warned about potentially major behavioural changes.

15. Fibrotic Reactions with Older Dopamine Agonists

The table correctly lists fibrotic reactions, but these are particularly associated with the older ergot-derived dopamine agonists, such as bromocriptine and pergolide.

They may cause:

Pleuropulmonary fibrosis.

Retroperitoneal fibrosis.

Cardiac valvular fibrosis.

This is an important reason why pergolide is no longer routinely used in many countries and non-ergot dopamine agonists are generally preferred.

16. Selegiline

Selegiline is a selective monoamine oxidase-B (MAO-B) inhibitor.

MAO-B is involved in dopamine metabolism within the brain.

By inhibiting MAO-B:

Dopamine breakdown ↓ → dopamine availability in the brain ↑ → Parkinsonian symptoms improve.

17. Other MAO-B Inhibitors

Other drugs in this class include:

Rasagiline.

Safinamide.

These agents may be used alone in selected early disease or as adjuncts to levodopa to reduce motor fluctuations.

18. Does Selegiline Slow Disease Progression?

The original table states that selegiline “may slow progression of disease.”

This should be updated.

MAO-B inhibitors provide symptomatic benefit, but convincing evidence that selegiline meaningfully prevents or reverses the underlying neurodegenerative progression of Parkinson disease is lacking.

Therefore, it is better remembered as a symptomatic and adjunctive treatment, rather than a proven neuroprotective treatment.

19. Adverse Effects of Selegiline

Potential adverse effects include:

Postural hypotension.

Hallucinations.

Confusion.

Nausea.

Dyskinesia when combined with levodopa.

Because selegiline has metabolites with stimulant properties, it may also contribute to insomnia, particularly if taken late in the day.

20. Entacapone

Entacapone is a catechol-O-methyltransferase (COMT) inhibitor.

It is used together with levodopa rather than as effective Parkinson therapy on its own.

COMT normally contributes to the peripheral metabolism of levodopa.

21. Mechanism of Entacapone

Entacapone inhibits peripheral COMT and therefore reduces the breakdown of levodopa.

This results in:

Reduced peripheral levodopa metabolism → prolonged levodopa availability → more sustained dopaminergic effect.

It is particularly useful for patients who experience end-of-dose wearing-off.

22. Entacapone and Wearing-Off

A patient may initially respond well to levodopa but find that symptoms return before the next dose.

Adding entacapone can extend the duration of each levodopa dose.

Therefore:

Levodopa wearing-off → consider a COMT inhibitor such as entacapone.

23. Adverse Effects of Entacapone

Important adverse effects include:

Diarrhoea.

Nausea.

Postural hypotension.

Increased levodopa-related dyskinesia.

Entacapone can also cause harmless orange-brown or reddish-brown discoloration of urine.

The old table describes this simply as “brown urine.”

24. Other COMT Inhibitors

Other COMT inhibitors include:

Opicapone.

Tolcapone.

Tolcapone acts both centrally and peripherally but is used much less because of the risk of serious hepatotoxicity and the need for appropriate liver monitoring.

25. Anticholinergic Drugs

Anticholinergic drugs used in Parkinsonism are predominantly central antimuscarinic agents.

Examples from the table include:

Benztropine.

Procyclidine.

Another traditional example is trihexyphenidyl (benzhexol).

26. Mechanism of Anticholinergic Drugs

Loss of dopamine in Parkinson disease creates a relative excess of cholinergic activity within the basal ganglia.

Antimuscarinic drugs reduce this cholinergic influence.

They are particularly useful for reducing:

Tremor.

Rigidity to some extent.

They have relatively little effect on bradykinesia.

27. Drug-Induced Parkinsonism

Anticholinergic drugs can be particularly useful for drug-induced Parkinsonism, such as Parkinsonian symptoms caused by dopamine-blocking antipsychotic drugs.

However, the underlying medication should also be reviewed whenever possible.

They are not usually preferred as routine first-line treatment for typical Parkinson disease, particularly in older patients.

28. Adverse Effects of Anticholinergic Drugs

Because these drugs block muscarinic acetylcholine receptors, they produce characteristic anticholinergic adverse effects:

Dry mouth.

Constipation.

Urinary retention.

Blurred vision.

Tachycardia.

29. Psychiatric and Cognitive Effects

Central anticholinergic effects can cause:

Confusion.

Memory impairment.

Hallucinations.

Agitation.

Because these effects are particularly problematic in older patients, anticholinergic drugs are generally avoided or used very cautiously in elderly people or patients with cognitive impairment.

30. Drugs Used in Parkinsonism – Note Form

Levodopa + carbidopa/benserazide: levodopa enters the brain and is converted to dopamine; the peripheral decarboxylase inhibitor prevents excessive peripheral conversion.

Main benefit of levodopa: strongest symptomatic improvement, particularly for bradykinesia and rigidity.

Major long-term levodopa problems: wearing-off, on–off fluctuations and dyskinesia.

Other levodopa adverse effects: nausea, postural hypotension, hallucinations and confusion.

Dopamine agonists: directly stimulate dopamine receptors.

Modern dopamine agonists: pramipexole, ropinirole and rotigotine; apomorphine is important in selected advanced disease.

Major dopamine-agonist adverse effects: hallucinations, hypotension, sleep attacks and impulse-control disorders.

Bromocriptine/pergolide: older ergot dopamine agonists associated with fibrotic complications; pergolide is largely obsolete in modern Parkinson treatment.

Selegiline: MAO-B inhibitor → decreases dopamine breakdown.

MAO-B inhibitors: provide symptomatic benefit but should not be regarded as proven treatments that stop Parkinson disease progression.

Entacapone: COMT inhibitor → reduces peripheral levodopa metabolism and prolongs levodopa action.

Best use of entacapone: end-of-dose wearing-off.

Entacapone adverse effects: diarrhoea, dyskinesia and harmless urine discoloration.

Anticholinergics: benztropine and procyclidine.

Anticholinergic benefit: mainly improve tremor; relatively little effect on bradykinesia.

Anticholinergic adverse effects: dry mouth, urinary retention, constipation, blurred vision, tachycardia, confusion and psychiatric disturbance.

Key Clinical Pattern

The easiest way to remember Parkinson drugs is according to where they increase dopaminergic activity:

Levodopa → supplies the precursor for dopamine.

Dopamine agonists → directly stimulate dopamine receptors.

MAO-B inhibitors → reduce dopamine breakdown in the brain.

COMT inhibitors → prolong the effect of levodopa.

Anticholinergics → reduce relative cholinergic activity, particularly helping tremor.

For examinations, remember the characteristic drug–adverse effect associations:

Levodopa → dyskinesia + on–off fluctuations + hallucinations.

Dopamine agonists → impulse-control disorders + hallucinations + sleep attacks.

Selegiline → postural hypotension + hallucinations ± insomnia.

Entacapone → diarrhoea + urine discoloration + increased dyskinesia.

Anticholinergics → dry mouth + constipation + urinary retention + confusion.

Medicine – Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is a severe, progressive X-linked recessive muscular dystrophy caused by pathogenic variants in the DMD gene, resulting in an almost complete absence of functional dystrophin protein.

Because dystrophin is essential for maintaining the structural stability of muscle fibres during contraction, its absence leads to repeated muscle-fibre injury, degeneration, and replacement by fat and connective tissue.

1. Inheritance

DMD is inherited in an X-linked recessive pattern.

It therefore predominantly affects boys, while females are usually carriers.

Some female carriers can develop mild muscle weakness or cardiomyopathy because of skewed X-chromosome inactivation.

2. Dystrophin Deficiency

The DMD gene encodes dystrophin, a structural protein that links the muscle-cell cytoskeleton to the surrounding extracellular matrix.

In Duchenne muscular dystrophy, functional dystrophin is essentially absent.

This makes the muscle membrane fragile during contraction and results in progressive muscle-cell damage.

3. Comparison with Becker Muscular Dystrophy

Duchenne and Becker muscular dystrophy are caused by mutations in the same gene.

The key difference is:

Duchenne muscular dystrophy → dystrophin absent or nearly absent.

Becker muscular dystrophy → dystrophin reduced or structurally abnormal but partly functional.

As a result, Duchenne disease presents earlier and is more severe.

4. Age of Presentation

Symptoms usually become apparent in early childhood, often between about 2 and 5 years of age.

Parents may notice delayed motor milestones, frequent falls, difficulty running, or difficulty climbing stairs.

5. Girdle Muscle Weakness

The weakness is predominantly proximal, especially affecting the pelvic-girdle muscles.

Children may have difficulty:

Running.

Jumping.

Climbing stairs.

Getting up from the floor.

Keeping up with other children.

As weakness progresses, the shoulder-girdle muscles also become affected.

6. Waddling Gait

Weakness of the hip abductor and pelvic-girdle muscles causes a characteristic waddling gait.

The child shifts the trunk from side to side while walking to compensate for weak hip muscles.

Lumbar lordosis may also become more pronounced.

7. Gowers Sign

A classic clinical finding is Gowers sign.

When rising from the floor, the child uses the hands to push on the knees and then “climbs” up the thighs.

This occurs because the hip and thigh muscles are too weak to raise the body efficiently without assistance from the upper limbs.

Therefore:

Gowers sign = proximal pelvic-girdle weakness.

8. Calf Pseudohypertrophy

The calf muscles may appear unusually large.

This is called calf pseudohypertrophy.

The enlargement is not caused by increased functional muscle tissue. Instead, damaged muscle fibres are progressively replaced by fat and connective tissue.

Thus:

Large calves + weak child → think Duchenne muscular dystrophy.

9. Raised Creatine Kinase

Serum creatine kinase (CK) is typically markedly elevated, often many times above the normal range.

CK leaks from damaged muscle fibres into the blood.

The CK may be very high even before severe weakness becomes obvious.

10. Other Laboratory Findings

Other muscle-derived enzymes may also be elevated, including:

AST.

ALT.

This is important because elevated transaminases in a child with muscle weakness may be mistakenly interpreted as primary liver disease.

A markedly elevated CK points toward skeletal-muscle injury.

11. Loss of Walking Ability

Without effective modern disease-modifying management, boys with classic DMD historically lost independent walking ability around the early teenage years, often near 12 years of age.

However, this older figure is no longer absolute.

Modern corticosteroid therapy, rehabilitation, cardiac care, respiratory support, and newer targeted treatments can prolong ambulation and survival.

12. Contractures

As muscle weakness progresses, patients may develop joint contractures.

Common sites include:

Ankles.

Knees.

Hips.

Tightness of the Achilles tendons may contribute to toe walking.

Regular stretching and physiotherapy are important to delay contracture formation.

13. Scoliosis

Loss of trunk muscle strength can lead to scoliosis, particularly after loss of independent ambulation.

Severe scoliosis can further impair respiratory mechanics.

Postural management and orthopaedic assessment are therefore important.

14. Respiratory Muscle Weakness

Progressive weakness eventually affects the respiratory muscles.

This can cause:

Weak cough.

Poor secretion clearance.

Recurrent chest infections.

Nocturnal hypoventilation.

Progressive respiratory failure.

Respiratory complications were historically a major cause of death.

15. Cardiac Involvement

Dystrophin is also important in cardiac muscle.

Patients commonly develop dilated cardiomyopathy.

They may also develop:

Left ventricular dysfunction.

Cardiac fibrosis.

Arrhythmias.

Cardiac disease may progress even when skeletal-muscle symptoms dominate clinically.

16. Cardiac Monitoring

Regular cardiac surveillance is therefore essential.

This may include:

ECG.

Echocardiography.

Cardiac MRI.

Early treatment of cardiomyopathy can improve long-term outcomes.

17. Cognitive and Neurodevelopmental Features

Dystrophin is also expressed in the brain.

Some boys with DMD may have:

Learning difficulties.

Attention problems.

Autism-spectrum features.

Speech or language delay.

Intellectual ability varies widely, and severe cognitive impairment is not universal.

18. Diagnosis

Diagnosis is usually established by:

Clinical features.

Very high serum CK.

Genetic testing for pathogenic variants in the DMD gene.

Genetic confirmation is important because it establishes the diagnosis and may determine eligibility for mutation-specific therapies.

19. Muscle Biopsy

Muscle biopsy is now less commonly required when genetic testing confirms the diagnosis.

When performed, it may demonstrate severe dystrophic changes and absence of dystrophin on immunostaining.

20. Genetic Counselling

Because DMD is X-linked, genetic counselling is important.

Carrier testing may be offered to appropriate female relatives.

Carrier women may also require cardiac surveillance because they can develop cardiomyopathy even without significant skeletal-muscle weakness.

21. Corticosteroid Therapy

Corticosteroids such as prednisolone or deflazacort have long been used to slow the decline in muscle strength.

They can help:

Prolong walking ability.

Preserve upper-limb function.

Delay scoliosis.

Support respiratory function.

Treatment requires monitoring for long-term adverse effects.

22. Modern Disease-Modifying Therapy

Management has expanded beyond supportive care.

Selected patients may be eligible for mutation-specific treatments, including exon-skipping therapies or other targeted approaches, depending on the exact DMD gene variant and local regulatory approval.

Gene-based treatments are also an evolving area of DMD management.

23. Respiratory Management

Respiratory care includes:

Regular pulmonary-function assessment.

Airway-clearance techniques.

Assisted cough when needed.

Non-invasive ventilation for nocturnal hypoventilation or respiratory failure.

These interventions have substantially improved survival.

24. Cardiac Treatment

Cardiomyopathy may be treated with standard cardiac therapies.

These can include:

ACE inhibitors or ARBs.

Beta-blockers.

Mineralocorticoid-receptor antagonists in appropriate patients.

Early cardiac treatment is an important part of modern DMD care.

25. Prognosis

The older statement that patients generally die from respiratory or cardiac failure in their 20s or early 30s reflects historical experience.

With modern multidisciplinary care, many patients now survive well into adulthood, and survival continues to improve.

The major long-term threats remain:

Cardiomyopathy.

Respiratory failure.

But both can now be monitored and treated much more effectively than in the past.

26. Duchenne Muscular Dystrophy – Note Form

Inheritance: X-linked recessive.

Gene: DMD gene.

Protein abnormality: functional dystrophin essentially absent.

Onset: early childhood.

Weakness: progressive proximal pelvic- and shoulder-girdle weakness.

Gait: waddling gait.

Gowers sign: uses hands to climb up the legs when standing from the floor.

Calves: pseudohypertrophy due to fat and connective-tissue replacement.

CK: markedly raised.

Mobility: walking ability is progressively lost, historically around early adolescence, but modern treatment may prolong ambulation.

Respiratory complication: progressive respiratory muscle weakness and respiratory failure.

Cardiac complication: dilated cardiomyopathy and arrhythmias.

Diagnosis: high CK + DMD genetic testing.

Management: corticosteroids, physiotherapy, cardiac surveillance, respiratory support, genetic counselling, and selected mutation-specific therapies.

Key Clinical Pattern

Remember DMD as:

Young boy + proximal muscle weakness + waddling gait + Gowers sign + calf pseudohypertrophy + very high CK.

The core molecular defect is:

X-linked DMD mutation → absent dystrophin.

The easiest comparison with Becker muscular dystrophy is:

Duchenne → absent dystrophin → early onset + severe disease.

Becker → some dystrophin remains → later onset + milder disease.

Medicine – Becker Muscular Dystrophy

Becker muscular dystrophy (BMD) is an inherited X-linked recessive muscular dystrophy caused by abnormalities in the dystrophin protein. It is closely related to Duchenne muscular dystrophy (DMD), but the dystrophin abnormality is usually less severe, so the disease presents later and progresses more slowly.

1. Inheritance

Becker muscular dystrophy is inherited in an X-linked recessive pattern.

Therefore, it mainly affects males, while females are usually carriers, although some female carriers can develop muscle weakness or cardiac involvement.

The abnormal gene is the DMD gene on the X chromosome, which encodes dystrophin.

2. Dystrophin Abnormality

Dystrophin is a structural protein that helps connect the muscle-cell cytoskeleton to the surrounding extracellular matrix.

It stabilises the muscle membrane during contraction.

In Becker muscular dystrophy, dystrophin is usually reduced in quantity or abnormal in structure, but some functional protein remains.

This is the major reason BMD is milder than Duchenne muscular dystrophy.

3. Comparison with Duchenne Muscular Dystrophy

The key molecular distinction is:

Duchenne muscular dystrophy → dystrophin is essentially absent or severely deficient.

Becker muscular dystrophy → dystrophin is present but reduced or abnormal.

Because Becker patients retain some functional dystrophin, muscle-cell damage progresses more slowly.

4. Later Age of Onset

Becker muscular dystrophy generally manifests later than Duchenne muscular dystrophy.

Symptoms may begin in later childhood, adolescence, or occasionally adulthood.

This contrasts with Duchenne muscular dystrophy, which usually becomes clinically apparent in early childhood.

5. Milder Clinical Course

BMD generally causes a milder and more slowly progressive muscular dystrophy than DMD.

Patients often remain independently ambulant for much longer.

However, severity varies considerably, and some patients can still develop major skeletal-muscle, respiratory, or cardiac complications.

6. Muscle Weakness

The typical pattern is progressive proximal muscle weakness, especially involving the pelvic girdle and lower limbs.

Patients may develop difficulty:

Running.

Climbing stairs.

Getting up from the floor.

Rising from a chair.

Walking long distances.

Weakness generally progresses more slowly than in DMD.

7. Gowers Sign

Patients with significant proximal lower-limb weakness may demonstrate Gowers sign.

When rising from the floor, the patient uses the hands to “climb up” the thighs because the hip and thigh muscles are weak.

Gowers sign is not specific to Becker muscular dystrophy, but it is characteristic of proximal muscular weakness.

8. Calf Pseudohypertrophy

Calf pseudohypertrophy may occur.

The calves appear enlarged, but the enlargement is partly due to replacement of muscle tissue by fat and connective tissue, rather than true increase in functional muscle mass.

This finding is seen in both Becker and Duchenne muscular dystrophy.

9. Serum Creatine Kinase

Serum creatine kinase (CK) is usually markedly elevated because damaged skeletal muscle releases CK into the bloodstream.

An elevated CK may be detected even before severe clinical weakness develops.

However, CK levels alone cannot distinguish Becker from Duchenne muscular dystrophy.

10. Cardiac Involvement

Cardiac disease is an important complication of Becker muscular dystrophy.

Patients may develop dilated cardiomyopathy and cardiac rhythm abnormalities.

Importantly, the severity of cardiac disease does not always parallel the severity of skeletal-muscle weakness.

Therefore, even relatively mobile patients may require regular cardiac surveillance.

11. Female Carriers and the Heart

Female carriers of dystrophin mutations can occasionally develop cardiomyopathy, even when skeletal-muscle symptoms are minimal or absent.

This is why carrier identification and appropriate cardiac monitoring can be clinically important.

12. Respiratory Involvement

Respiratory muscle weakness can develop as the disease progresses.

This may lead to:

Reduced respiratory reserve.

Sleep-related hypoventilation.

Recurrent respiratory infections.

Respiratory failure in advanced disease.

Respiratory involvement generally occurs later than in classic Duchenne muscular dystrophy.

13. Diagnosis

Diagnosis is primarily based on genetic testing of the DMD gene.

This can identify deletions, duplications, or other pathogenic variants affecting dystrophin production.

Genetic testing has largely reduced the need for muscle biopsy in straightforward cases.

14. Muscle Biopsy

If genetic testing is inconclusive, muscle biopsy may sometimes be useful.

Immunohistochemical or protein analysis can demonstrate dystrophin that is reduced in amount or abnormal in size.

This contrasts with DMD, where dystrophin is usually nearly or completely absent.

15. Management

Management is multidisciplinary and focuses on preserving mobility, preventing complications, and monitoring cardiac and respiratory function.

Care may involve:

Neurology.

Physiotherapy.

Cardiology.

Respiratory medicine.

Rehabilitation.

Genetic counselling.

16. Physiotherapy

Physiotherapy helps maintain:

Joint mobility.

Muscle function.

Posture.

Walking ability.

Stretching and contracture prevention are important as weakness progresses.

Excessive high-intensity exercise that causes muscle injury should generally be avoided.

17. Cardiac Management

Patients require periodic assessment of cardiac function.

This may include:

ECG.

Echocardiography.

Cardiac MRI when indicated.

Cardiomyopathy may be treated with standard heart-failure therapies such as ACE inhibitors or related agents and beta-blockers when appropriate.

18. Genetic Counselling

Because BMD is X-linked, genetic counselling is important for affected families.

Carrier testing can help identify female relatives who may have reproductive implications or require cardiac surveillance.

Prenatal or reproductive genetic options may also be discussed when appropriate.

19. Becker versus Duchenne – Note Form

Inheritance in both: X-linked recessive.

Gene in both: DMD gene.

Protein in both: dystrophin.

Duchenne: dystrophin essentially absent.

Becker: dystrophin reduced or structurally abnormal but partly functional.

Duchenne onset: early childhood.

Becker onset: later childhood, adolescence, or adulthood.

Duchenne course: more severe and rapidly progressive.

Becker course: milder and more slowly progressive.

Both may show: proximal weakness, Gowers sign, calf pseudohypertrophy, elevated CK and cardiomyopathy.

Key Clinical Pattern

Remember Becker muscular dystrophy as:

X-linked dystrophin disorder + later onset + milder progression than Duchenne.

The easiest distinction is:

Duchenne → little or no functional dystrophin.

Becker → some functional dystrophin remains.

Therefore:

More dystrophin → later presentation and milder disease.