Infectious Disease and Microbiology






Kawasaki syndrome (Kawasaki disease, KD)




Kawasaki syndrome is an acute, self-limited systemic vasculitis that primarily affects young children, especially those under 5 years of age. It is also known as mucocutaneous lymph node syndrome. Although the disease often resolves on its own, it is clinically significant because it can lead to serious cardiovascular complications, particularly coronary artery aneurysms.


The disease occurs worldwide but is most common in Japan, with most cases seen in children younger than 5 years. It can occur throughout the year, with peaks during winter and spring. Risk factors include recent respiratory infections and environmental exposures such as dust and mites. Genetic susceptibility also plays a role, with involvement of pathways such as caspase-3 and TGF-beta.


Kawasaki syndrome involves inflammation of medium and small blood vessels. In the early stage, there is endothelial swelling and inflammation, which later progresses to widespread systemic inflammation affecting multiple organs, especially the heart. Although the exact cause remains unknown, the condition is believed to be triggered by an infectious agent, possibly through a superantigen-mediated immune response.


Clinically, the diagnosis is based on the presence of fever lasting at least five days along with characteristic features. These include a polymorphous rash, bilateral non-purulent conjunctivitis, oral changes such as cracked lips and strawberry tongue, swelling and redness of the hands and feet followed by peeling, and cervical lymphadenopathy. Incomplete forms of the disease may occur and should still be treated if suspected. Other symptoms may include irritability, joint pain, myocarditis, pericarditis, aseptic meningitis, and gastrointestinal symptoms.


Laboratory findings commonly show anemia, leukocytosis, and thrombocytosis, particularly in later stages. Inflammatory markers such as ESR and CRP are elevated, and hypoalbuminemia and elevated liver enzymes may also be present. Echocardiography is essential to evaluate for coronary artery involvement, while ECG may reveal arrhythmias or other cardiac changes.


Management should be initiated promptly to reduce the risk of complications. The mainstay of treatment is intravenous immunoglobulin (IVIG), given as a single high-dose infusion, with a repeat dose if fever persists. Aspirin is also used, initially at high doses for its anti-inflammatory effect and later at lower doses for its antiplatelet properties. In resistant cases, corticosteroids or agents such as infliximab may be used. Patients with coronary complications may require anticoagulation and specialist cardiac care.


The prognosis is generally good when treated early. Without treatment, a significant proportion of patients develop coronary artery aneurysms, but this risk is markedly reduced with timely therapy. Long-term follow-up with echocardiography is important, especially in those with cardiac involvement.


Complications are mainly cardiovascular and include coronary artery aneurysms, myocardial infarction, myocarditis, and pericarditis, with myocardial infarction being the most common cause of death. Non-cardiac complications may include hearing loss, arthritis, pneumonitis, and macrophage activation syndrome.

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Infectious Disease and Microbiology - Keratitis




Keratitis refers to inflammation of the cornea that may be caused by infectious or noninfectious processes. Infectious keratitis can result from bacteria, viruses, fungi, or parasites, and bacterial keratitis is often referred to as a corneal ulcer. A major global cause of keratitis-related blindness is trachoma due to Chlamydia trachomatis, which leads to chronic inflammation, eyelid deformities, and corneal scarring.


The condition occurs worldwide, with bacterial keratitis being more common among contact lens users. Risk factors include disruption of the corneal epithelial surface, poor contact lens hygiene, overnight lens use, and ocular trauma. In critically ill patients, factors such as inability to close the eyes, reduced blinking, and dry eye contribute to risk. Fungal keratitis is more common in warm climates and often follows trauma with plant material, while trachoma is associated with poor hygiene and limited access to water.


The pathophysiology involves a break in the corneal epithelium that allows microorganisms to enter and proliferate in the corneal stroma. Some organisms possess adhesins that facilitate attachment to corneal cells. Viral causes such as Herpes simplex virus type 1 can remain latent in the trigeminal ganglion and reactivate, leading to recurrent disease. Similarly, Varicella zoster virus may reactivate later in life, causing herpes zoster ophthalmicus when the trigeminal nerve is involved.


A wide range of organisms can cause keratitis. Bacterial causes include Pseudomonas, Staphylococcus, and Streptococcus species, with Pseudomonas being particularly aggressive in contact lens users. Viral causes include HSV and VZV, with HSV producing characteristic dendritic lesions. Fungal organisms such as Aspergillus and Fusarium cause more indolent infections, while parasites such as Acanthamoeba can produce severe pain and characteristic ring-shaped infiltrates.


Patients typically present with eye pain, redness, foreign body sensation, photophobia, tearing, discharge, and reduced vision. Severe pain that is disproportionate to clinical findings is suggestive of Acanthamoeba infection. Viral keratitis may lead to reduced corneal sensation. Herpes zoster ophthalmicus may be preceded by a flu-like illness and is associated with a dermatomal rash, especially involving the tip of the nose.


On examination, slit-lamp findings include epithelial defects, stromal infiltrates, and anterior chamber inflammation. Fluorescein staining highlights epithelial defects. Severe cases may show hypopyon. Bacterial ulcers may appear as rapidly spreading infiltrates, while fungal keratitis often shows feathery borders and satellite lesions. HSV infection classically produces branching dendritic ulcers, while late Acanthamoeba infection may show a ring infiltrate.


Diagnosis is primarily clinical but supported by laboratory studies. Corneal scrapings are obtained for staining and culture to identify the causative organism. Special stains and media are used depending on suspected pathogens. PCR and viral testing may be used for herpetic infections, while confocal microscopy can help identify Acanthamoeba cysts.


Management depends on the underlying cause but must be initiated promptly. Suspected bacterial keratitis requires immediate empiric broad-spectrum topical antibiotics, often administered hourly. Severe cases may require fortified antibiotic drops. Fungal keratitis is treated with topical antifungals such as natamycin or amphotericin B, often for prolonged periods. Acanthamoeba infections require specific agents such as polyhexamethylene biguanide and are difficult to eradicate. Viral keratitis due to HSV is treated with topical antivirals, while deeper stromal disease may require cautious use of topical steroids along with antiviral coverage. Herpes zoster ophthalmicus is treated with systemic antiviral therapy.


Prognosis depends on the severity, location, and timeliness of treatment. Early treatment generally leads to good outcomes, but delayed therapy can result in significant visual impairment. Complications include corneal scarring, thinning, perforation, and secondary infections such as endophthalmitis. Chronic or recurrent infections, particularly with HSV, may lead to permanent visual loss and require surgical intervention such as corneal transplantation.

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Infectious Disease and Microbiology - Legionnaires disease




Legionnaires’ disease is a form of pneumonia caused by gram-negative bacteria of the Legionellaceae family, most notably Legionella pneumophila. It was first identified in 1976 following an outbreak among attendees of an American Legion convention. A milder, non-pneumonic illness caused by the same organism is known as Pontiac fever. Together, these conditions are referred to as legionellosis.


The disease is relatively common among atypical pneumonias, accounting for a proportion of community-acquired pneumonia cases requiring hospitalization. It is associated with outbreaks linked to contaminated water systems such as cooling towers, air conditioning units, spas, and fountains. Cases occur more frequently in warmer months when such systems are widely used. Risk factors include older age, smoking, chronic lung disease, immunosuppression, and recent exposure to contaminated water sources or travel.


Legionella organisms are aerobic, intracellular bacteria that thrive in aquatic environments. They can proliferate in man-made water systems and are transmitted primarily through inhalation of aerosolized contaminated water. Once inhaled, the bacteria infect alveolar macrophages, where they replicate intracellularly. The immune response involves activation of T cells, which enhance macrophage-mediated killing.


Clinically, Legionnaires’ disease presents with high fever, malaise, myalgias, and headache, followed by respiratory symptoms such as cough, which may become productive, and chest pain. Gastrointestinal symptoms, including diarrhea and vomiting, are common and can help distinguish it from other pneumonias. Neurological symptoms such as confusion or encephalopathy may occur in severe cases. The incubation period is typically 2 to 10 days. In contrast, Pontiac fever presents as a self-limited febrile illness without pneumonia.


On physical examination, patients may have fever, tachypnea, and signs of lung consolidation such as rales. Relative bradycardia, hypotension, and altered mental status may also be present. Laboratory findings often include hyponatremia, elevated liver enzymes, and inflammatory markers. Diagnosis is supported by detection of Legionella antigen in urine, which is particularly useful early in the disease but mainly detects serogroup 1. Culture on specialized media and PCR testing may also be used.


Chest imaging typically shows patchy or lobar infiltrates, often involving the lower lobes, and pleural effusions may be present. Radiographic resolution can be slow and may lag behind clinical improvement.


Treatment involves prompt initiation of appropriate antibiotics. First-line therapy includes macrolides such as azithromycin or fluoroquinolones, with the latter preferred in severe cases. Intravenous therapy is used initially in hospitalized patients, followed by oral therapy once clinical improvement occurs. Treatment duration is generally 10–14 days, but longer courses may be required in immunocompromised individuals.


The prognosis depends on the patient’s overall health and comorbidities, with mortality rates ranging from 5% to 30%. Complications may include respiratory failure, multiorgan dysfunction, and extrapulmonary involvement such as myocarditis or renal failure. Early recognition and treatment are critical to improving outcomes.

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Infectious Disease and Microbiology - Larva migrans syndromes




Larva migrans syndromes represent a group of conditions caused by the migration of helminth larvae through human tissues, affecting the skin, internal organs, or eyes. These syndromes include cutaneous, visceral, and ocular forms, depending on where the larvae migrate. Humans are accidental hosts, and the parasites are unable to complete their life cycle, leading instead to tissue inflammation and damage.


The condition is seen worldwide but is more common in tropical and subtropical regions. Infections are particularly frequent in children, especially those under 6 years old. Cutaneous larva migrans is the most common tropical dermatosis, often acquired from contaminated beaches or soil. Visceral and ocular forms are most commonly caused by Toxocara canis and, less frequently, Toxocara cati, with a significant proportion of the population showing evidence of past infection.


Risk factors include contact with soil contaminated by dog or cat feces, poor hand hygiene, and geophagia. Children who play in contaminated environments are particularly at risk. Prevention focuses on avoiding direct contact with contaminated soil, wearing protective footwear, maintaining good hygiene, and regular deworming of pets.


The pathophysiology varies by form. In visceral larva migrans, eggs are ingested and hatch in the intestine, after which larvae migrate via the bloodstream to organs such as the liver, lungs, and central nervous system. These larvae may persist for years, causing chronic inflammation. In cutaneous larva migrans, larvae penetrate the skin but remain confined to the epidermis, migrating and forming characteristic tracks.


Cutaneous larva migrans, commonly caused by Ancylostoma braziliense, presents with intensely itchy, serpiginous, erythematous skin lesions that slowly advance over time. These lesions are most often found on the feet, legs, or areas exposed to contaminated ground. Visceral larva migrans may present with fever, fatigue, abdominal pain, cough, and hepatomegaly, while ocular larva migrans may cause visual disturbances, floaters, or even unilateral blindness due to retinal inflammation.


Physical examination findings vary with the syndrome. Cutaneous disease shows a creeping eruption on the skin, while visceral disease may show hepatomegaly, wheezing, or lymphadenopathy. Ocular disease may reveal retinal granulomas, uveitis, or optic nerve involvement on funduscopic examination.


Laboratory findings in visceral disease often include marked eosinophilia, leukocytosis, and elevated IgE levels. Serologic testing such as ELISA can support the diagnosis. Imaging studies may reveal hepatic or pulmonary lesions, while ocular disease is diagnosed primarily through ophthalmologic examination. Larvae are rarely identified directly in tissue samples.


Treatment depends on the clinical form. Cutaneous larva migrans is treated with antiparasitic agents such as albendazole or ivermectin, and symptoms usually resolve as the larvae die. Visceral larva migrans may not require treatment in mild cases, but severe disease is managed with albendazole or mebendazole. Ocular disease may also require antiparasitic therapy, often combined with corticosteroids to reduce inflammation, although treatment must be carefully managed to avoid worsening ocular damage.


Prognosis is generally good for cutaneous and most visceral cases, with spontaneous resolution common. However, ocular larva migrans carries a risk of permanent vision loss. Complications may include secondary bacterial infection in cutaneous disease, and in severe visceral cases, involvement of the brain, heart, or lungs.

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Infectious Disease and Microbiology - Leishmaniasis




Leishmaniasis is a parasitic disease caused by protozoa of the genus Leishmania and transmitted through the bite of infected sandflies. It presents in three main clinical forms: cutaneous, mucosal, and visceral, with manifestations depending largely on the host immune response and the infecting species. The disease is widespread, with millions of cases globally and hundreds of millions of people at risk, particularly in tropical and subtropical regions.


Transmission occurs when infected sandflies inoculate promastigotes into the skin. These are taken up by macrophages, where they transform into amastigotes and multiply intracellularly. The parasites preferentially infect cells of the reticuloendothelial system. Disease severity is influenced by parasite burden, species type, and the host’s immune status. Immunocompromised individuals, especially those with HIV, are at increased risk of severe disease.


Cutaneous leishmaniasis typically begins as a papule at the site of the bite, which gradually enlarges, crusts, and ulcerates. The ulcer is usually painless, with raised borders and a granulating base, and may persist for months or even years. Mucosal leishmaniasis, most commonly associated with Leishmania braziliensis, affects the mucous membranes of the nose, mouth, and throat, potentially causing destructive lesions such as nasal septum perforation and voice changes.


Visceral leishmaniasis, also known as kala-azar, is the most severe form and is commonly caused by Leishmania donovani and Leishmania infantum. It presents with prolonged fever, weight loss, hepatosplenomegaly, anemia, and pancytopenia. Without treatment, it carries a high mortality rate. In advanced cases, patients may develop cachexia, edema, and profound immune dysfunction.


Diagnosis is confirmed by demonstrating the parasite in tissue samples such as bone marrow, spleen, liver, or skin lesions. Bone marrow aspiration is commonly used for visceral disease. PCR and serologic tests can support the diagnosis, particularly in visceral leishmaniasis, while skin tests are more useful in epidemiologic studies or cutaneous forms.


Treatment depends on the form and severity of disease. Liposomal amphotericin B is the treatment of choice for visceral leishmaniasis. Other agents include pentavalent antimonials, pentamidine, and newer oral therapies such as miltefosine. Many cases of cutaneous leishmaniasis resolve spontaneously, although treatment may be required for cosmetic reasons or severe disease. Mucosal disease requires systemic therapy due to its destructive nature.


The prognosis varies by form. Cutaneous disease generally has a good outcome, although scarring may occur. Visceral leishmaniasis is life-threatening if untreated but responds well to appropriate therapy. Mucosal disease can lead to significant morbidity and, in some cases, mortality. Complications include relapse, particularly in immunocompromised patients, and adverse effects from treatment such as toxicity from antimonial drugs.

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Infectious Disease and Microbiology - Leprosy




Leprosy is a chronic infectious disease caused by Mycobacterium leprae, an acid-fast, slow-growing intracellular organism that primarily affects the skin and peripheral nerves. The disease has a long incubation period, typically ranging from 5 to 7 years, and is transmitted mainly through prolonged close contact, likely via respiratory droplets or direct contact with untreated skin lesions. The organism has a predilection for cooler areas of the body, particularly the skin and peripheral nerves, where it infects Schwann cells and leads to nerve damage.


Leprosy remains a global health concern, although its prevalence has significantly declined over recent decades due to effective multidrug therapy. It is most common in endemic regions such as Brazil, India, Indonesia, and parts of Africa and Southeast Asia. Risk factors include close household contact with infected individuals, extremes of age (children and older adults), and impaired cell-mediated immunity. Genetic susceptibility also plays a role, influencing disease type and severity.


The clinical presentation varies widely depending on the host immune response. Patients typically present with hypopigmented or erythematous skin lesions accompanied by sensory loss, which is a hallmark feature. In tuberculoid disease, lesions are few, well-defined, and associated with localized nerve involvement. In contrast, lepromatous disease is characterized by numerous lesions, nodules, and diffuse skin involvement, often with more extensive nerve damage. Advanced cases may lead to deformities such as loss of eyebrows, hoarseness, and the classic saddle-nose deformity due to cartilage destruction.


Diagnosis is primarily clinical, based on the presence of characteristic skin lesions with sensory loss and thickened peripheral nerves. Skin smears or biopsies may be used to confirm the diagnosis, showing either granulomatous inflammation with few organisms in tuberculoid disease or numerous bacilli in lepromatous disease. The disease is also classified by the World Health Organization into paucibacillary and multibacillary forms based on lesion number and bacterial load.


Treatment involves prolonged multidrug therapy to prevent resistance and ensure cure. Multibacillary disease is treated with a combination of dapsone, rifampin, and clofazimine for an extended duration, while paucibacillary disease requires a shorter regimen with fewer drugs. Alternative agents such as fluoroquinolones, macrolides, and tetracyclines may be used in certain cases. Close monitoring is essential during therapy due to potential drug side effects and immune-mediated reactions.


The prognosis is excellent with appropriate treatment, but complications can arise, particularly involving the immune system. Type I (reversal) reactions involve worsening inflammation and nerve damage, while Type II reactions, known as erythema nodosum leprosum, present with systemic symptoms such as fever and painful nodules. Long-term complications include permanent nerve damage, disability, and deformities if untreated. Early diagnosis and adherence to therapy are crucial in preventing these outcomes.

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Infectious Disease and Microbiology - Laryngitis/Laryngotracheobronchitis (Croup)




Laryngitis refers to inflammation of the laryngeal mucosa, while laryngotracheobronchitis, commonly known as croup, involves inflammation of the subglottic airway, trachea, and bronchi. These conditions are most often caused by viral infections and typically present as part of an upper respiratory tract illness. Croup is particularly common in young children, especially between 3 months and 3 years of age, and tends to occur more frequently in boys.


The epidemiology reflects seasonal viral patterns. Laryngitis commonly occurs during winter in association with respiratory infections. Croup is most frequently caused by Parainfluenza virus type 1, especially in the fall, while Influenza virus and Respiratory syncytial virus contribute during winter and early spring. Other pathogens such as adenovirus, rhinovirus, enterovirus, and Mycoplasma pneumoniae may also be involved.


Risk factors for laryngitis include smoking, alcohol use, immunosuppression, and close contact with infected individuals. In croup, young age and possible variations in immune response play a major role. Prevention is mainly through avoidance of infected individuals and proper hand hygiene.


The underlying pathophysiology involves viral infection leading to inflammation, edema, and narrowing of the airway. In croup, subglottic swelling leads to airway obstruction, which is more pronounced in children due to their smaller airway diameter. This results in the characteristic stridor and respiratory distress.


Clinically, laryngitis presents with hoarseness, reduced voice pitch, and sometimes aphonia. In severe cases, airway obstruction may lead to stridor. Croup typically begins with fever followed by hoarseness and a distinctive “barking” cough. Inspiratory stridor, tachypnea, and chest wall retractions are common findings. In more severe cases, both inspiratory and expiratory stridor, wheezing, and signs of respiratory distress such as tachycardia and fatigue may develop.


Diagnosis is primarily clinical. Laboratory findings are usually normal, although hypoxemia may occur in severe cases. Imaging is not routinely required but may support the diagnosis. A classic anterior–posterior neck x-ray in croup shows subglottic narrowing known as the “steeple sign.”


Management depends on severity. Mild laryngitis is usually treated with supportive care such as humidified air, and medications are not required unless bacterial infection is suspected. In croup, corticosteroids such as dexamethasone are the mainstay of treatment and significantly improve symptoms. Nebulized epinephrine may be used in moderate to severe cases for temporary relief of airway obstruction, but patients require observation due to possible rebound symptoms. Supplemental oxygen is used in cases of hypoxemia, and severe cases may require intubation and mechanical ventilation.


The overall prognosis is excellent, with most cases resolving within a few days, although cough may persist longer. Complications are uncommon but may include airway obstruction and respiratory failure in severe croup. Rare complications include pneumothorax, pulmonary edema, and secondary infections. Long-term effects such as airway hyperreactivity or subglottic stenosis may occur in severe or recurrent cases.

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​Emergency and Acute Medicine – Wolff–Parkinson–White (WPW) Syndrome


Wolff–Parkinson–White syndrome (WPW) is a cardiac conduction disorder caused by the presence of an accessory pathway (Kent bundle) that bypasses the atrioventricular (AV) node, allowing premature ventricular activation (pre-excitation). On ECG, the WPW pattern is characterized by a short PR interval (<0.12 sec), a delta (Δ) wave representing early ventricular depolarization, and a widened QRS complex (>0.10 sec). While the ECG pattern alone is termed WPW pattern, the diagnosis of WPW syndrome requires both these findings and associated tachydysrhythmias.


Accessory pathways occur in approximately 0.1–0.3% of the population and are most commonly located along the left lateral free wall, followed by the posteroseptal region. Conduction through these pathways may occur in antegrade, retrograde, or bidirectional fashion. The most common arrhythmia associated with WPW is orthodromic atrioventricular re-entrant tachycardia (AVRT) (≈70%), where impulses travel down the AV node and return via the accessory pathway, producing a narrow complex tachycardia. Less commonly, antidromic AVRT (≈30%) occurs, with conduction down the accessory pathway and back through the AV node, resulting in a wide complex tachycardia. WPW can also precipitate atrial fibrillation with rapid ventricular response, which carries a risk of degeneration into ventricular fibrillation and sudden death.


Patients may be asymptomatic or present with palpitations, chest pain, dyspnea, dizziness, diaphoresis, or syncope. Physical findings depend on the rhythm and hemodynamic status, ranging from stable tachycardia to signs of instability such as hypotension, altered mental status, cyanosis, or pulmonary edema. Sudden cardiac death is rare but can occur (approximately 1 per 1,000 patient-years).


Diagnosis is based primarily on ECG findings. During sinus rhythm, the classic triad includes short PR interval, delta wave, and widened QRS complex. During tachyarrhythmias, ECG patterns vary depending on the mechanism: orthodromic AVRT typically produces a narrow complex tachycardia (150–250 bpm), while antidromic AVRT produces a wide complex tachycardia. Atrial fibrillation in WPW appears as an irregular wide complex rhythm with variable QRS morphology, which is a dangerous presentation.


Management depends on patient stability and rhythm type. Unstable patients (hypotension, chest pain, altered mental status) require immediate synchronized cardioversion, starting at 100 J and escalating as needed. In stable patients, initial management includes vagal maneuvers such as the Valsalva maneuver or carotid sinus massage (if no contraindications).


For narrow complex tachycardia (orthodromic AVRT), pharmacologic therapy includes Adenosine (6 mg rapid IV bolus, followed by 12 mg if needed; pediatric: 0.1–0.2 mg/kg) or calcium channel blockers when the diagnosis is certain. For wide complex tachycardia or suspected WPW with atrial fibrillation, Amiodarone (150 mg IV over 10 minutes, followed by infusion) or Procainamide (6–13 mg/kg IV infusion) are preferred.


Critically important: AV nodal–blocking agents such as β-blockers, calcium channel blockers, digoxin, and lidocaine must be avoided in patients with WPW and wide complex tachycardia or atrial fibrillation, as they may enhance conduction through the accessory pathway and precipitate fatal ventricular arrhythmias.


Disposition depends on clinical presentation. Patients with instability, syncope, or refractory arrhythmias require admission and monitoring. Most stable patients who convert to sinus rhythm can be discharged with cardiology follow-up, including consideration of electrophysiologic studies and radiofrequency ablation, which offers definitive treatment.


Key clinical pearls include maintaining a high suspicion for WPW in any tachydysrhythmia, avoiding AV nodal blockers in uncertain wide complex rhythms, and addressing anticoagulation if arrhythmia duration exceeds 48 hours due to embolic risk.

Emergency and Acute Medicine – Wheezing




Wheezing is a high-pitched, musical sound produced by turbulent airflow through narrowed airways, typically with a dominant frequency around 400 Hz. It occurs when airflow causes vibration of bronchial walls, similar to a reed instrument. Wheezing is most prominent when airway diameters are between 2–5 mm; larger airways produce lower-pitched sounds, while very small airways (<2 mm) may not transmit sound effectively due to energy loss. Airway narrowing may result from bronchoconstriction, inflammation, edema, or obstruction, and identifying the underlying mechanism is critical in acute care settings.


The causes of wheezing are broad and include both small-airway (pulmonary) and large-airway etiologies. Small-airway causes commonly include Asthma, Chronic Obstructive Pulmonary Disease, pulmonary edema, anaphylaxis, and aspiration. Certain drugs such as ACE inhibitors, β-blockers, aspirin, and NSAIDs may precipitate bronchospasm or allergic reactions. Less common causes include pulmonary embolism, carcinoid tumors, and occupational lung diseases like byssinosis. Large-airway causes include foreign body aspiration, vocal cord dysfunction, epiglottitis, tumors, and smoke inhalation. In pediatric populations, common causes include Bronchiolitis, asthma, croup, and congenital airway abnormalities such as tracheomalacia.


Clinically, wheezing presents as a whistling sound during breathing, often accompanied by dyspnea, cough, chest tightness, and respiratory distress. Diffuse wheezing suggests generalized airway disease such as asthma or pulmonary edema, while focal wheezing raises concern for localized obstruction such as pneumonia or foreign body. Associated findings may include tachypnea, tachycardia, cyanosis, and use of accessory muscles. A critical aspect of assessment is the patient’s mental status—fatigue, confusion, or lethargy may indicate impending respiratory failure and necessitate urgent airway management.


Evaluation begins with assessment of severity and oxygenation. Pulse oximetry is essential for monitoring oxygen saturation, while peak expiratory flow (PEF) helps quantify airway obstruction and response to treatment. Chest X-ray may be used to evaluate for pneumonia, pulmonary edema, or foreign body. Arterial blood gas (ABG) may be useful in severe cases to assess for rising CO₂ and acidosis, indicating respiratory fatigue. Additional investigations such as ECG or laryngoscopy may be indicated depending on suspected etiology.


Management focuses on rapid stabilization and reversal of airway obstruction. Initial treatment includes supplemental oxygen and airway support. Bronchodilators are first-line therapy, particularly Albuterol given as 2.5–5 mg nebulized every 20 minutes for 3 doses (pediatric: 0.15 mg/kg per dose, minimum 2.5 mg). Systemic corticosteroids such as Prednisone (40–80 mg PO; pediatric 1 mg/kg/day, max 60 mg) or Methylprednisolone (40–80 mg IV) are used to reduce airway inflammation and prevent relapse.


For moderate to severe cases, Ipratropium Bromide (0.5 mg nebulized every 20 minutes for 3 doses) can be added to β-agonist therapy. Additional therapies include magnesium sulfate (0.1 mL/kg of 50% solution IV over 20 minutes) in severe asthma, terbutaline (0.25 mg SC), and heliox in selected cases. In pediatric croup, racemic epinephrine (0.25–0.5 mL nebulized) may be used. Intubation is indicated for patients with impending respiratory failure, and Ketamine may be preferred due to its bronchodilatory properties.


Disposition depends on clinical response. Patients with persistent hypoxia, worsening symptoms, or underlying serious conditions require admission. Those who improve with treatment, achieve PEF >70% predicted, and maintain adequate oxygenation may be discharged with follow-up and clear return precautions. Patients with asthma should receive an action plan and appropriate outpatient referral.


A key clinical pearl is to always consider non-asthma causes of wheezing, especially in cases of focal findings or poor response to bronchodilators. Additionally, clinicians must be prepared for rapid airway deterioration, particularly when administering sedatives or managing severe respiratory distress.

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Infectious Disease and Microbiology: Herpes Zoster (Shingles)




Herpes zoster, commonly known as shingles, is a localized skin and nerve infection caused by reactivation of the Varicella zoster virus, the same virus responsible for chickenpox. After a primary infection, the virus remains dormant in sensory nerve ganglia for years. Reactivation later in life leads to herpes zoster, typically presenting as a painful, vesicular rash confined to a specific dermatome.


Epidemiologically, herpes zoster occurs worldwide and affects approximately 20% of individuals during their lifetime. The incidence increases significantly with age, particularly in those over 50 years. Nearly 90% of adults have evidence of prior VZV infection, placing them at risk for reactivation. Immunocompromised individuals—such as those with HIV infection, malignancies, or those receiving immunosuppressive therapy—are at particularly high risk and may develop more severe or disseminated disease.


The pathophysiology involves reactivation of latent virus within dorsal root or cranial nerve ganglia. The virus travels along sensory nerves to the skin, producing inflammation and the characteristic painful rash. The exact triggers for reactivation are not fully understood but are strongly associated with declining cell-mediated immunity, especially in aging or immunosuppressed individuals.


Clinically, patients typically present with localized pain, burning, or tingling in a dermatomal distribution, often preceding the rash by a few days. This is followed by the appearance of grouped vesicles on an erythematous base, usually confined to one side of the body. The thoracic and lumbar dermatomes are most commonly affected. Involvement of the trigeminal nerve may lead to ocular complications (herpes zoster ophthalmicus), while involvement of the geniculate ganglion can result in Ramsay Hunt syndrome, characterized by ear lesions and facial paralysis.


Diagnosis is primarily clinical, based on the typical unilateral dermatomal rash and associated pain. Laboratory tests such as PCR or serology can confirm the diagnosis but are rarely necessary in routine cases. Imaging or lumbar puncture may be required if central nervous system involvement is suspected.


Treatment focuses on antiviral therapy and pain management. First-line therapy includes oral acyclovir, while alternatives such as valacyclovir or famciclovir offer improved dosing convenience. In severe cases or immunocompromised patients, intravenous antivirals may be required. Adjunctive therapies, including analgesics and sometimes corticosteroids, may help reduce acute symptoms, although steroids do not prevent long-term complications.


The prognosis is generally good in immunocompetent individuals, but complications are not uncommon. The most significant is postherpetic neuralgia, a chronic pain condition that can persist long after the rash resolves, particularly in older adults. Other complications include secondary bacterial infection, ocular damage potentially leading to blindness, and, in severe cases, systemic involvement such as pneumonitis, hepatitis, or central nervous system disease.


Prevention includes vaccination against VZV, which reduces both the incidence of herpes zoster and the risk of postherpetic neuralgia. In high-risk individuals, prophylactic antivirals or immunoglobulin may be used following exposure.

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