Medicine – Cystic Fibrosis

Cystic fibrosis (CF) is a chronic, inherited multisystem disorder caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. The abnormal CFTR protein disrupts chloride and bicarbonate transport across epithelial surfaces, producing dehydrated, abnormally thick secretions. The respiratory and gastrointestinal systems are particularly affected, although CF can also cause diabetes, infertility, osteoporosis, and other complications.

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1. Autosomal Recessive Inheritance

Cystic fibrosis is inherited as an autosomal recessive disorder. An affected individual therefore inherits a disease-causing CFTR variant from each parent.

People with only one pathogenic variant are generally healthy carriers.

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2. Carrier Frequency

In populations of Northern European ancestry, approximately 1 in 25 people has traditionally been quoted as carrying a CFTR disease-causing variant.

Carrier frequency varies substantially between different ethnic and geographic populations.

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3. Incidence

Older teaching commonly gives an incidence of approximately 1 in 2,000–2,500 live births in White populations.

The incidence varies by population and has also changed with widespread carrier screening, prenatal testing, and demographic changes.

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4. CFTR Gene

The CFTR gene is located on the long arm of chromosome 7 and encodes the cystic fibrosis transmembrane conductance regulator protein.

CFTR functions primarily as an epithelial chloride and bicarbonate ion channel and also influences the activity of other ion channels.

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5. CFTR Mutations

More than 2,000 CFTR variants have now been identified, although not all cause cystic fibrosis.

The most common disease-causing variant is F508del (ΔF508), which results from deletion of three DNA bases and consequently loss of a phenylalanine residue at position 508 of the CFTR protein.

F508del causes abnormal protein folding and processing, so relatively little functional CFTR reaches the epithelial cell surface.

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6. Abnormal Chloride and Water Transport

Defective CFTR function disrupts the movement of chloride, bicarbonate, sodium, and water across epithelial surfaces.

In the respiratory tract, abnormal ion transport causes dehydration of airway secretions. The resulting mucus becomes thick and difficult to clear, impairing normal mucociliary clearance.

This promotes mucus plugging, chronic bacterial infection, inflammation, and progressive structural damage to the airways.

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Diagnosis

7. Sweat Chloride Test

The sweat chloride test remains an important diagnostic investigation because CFTR dysfunction causes abnormally high concentrations of chloride in sweat.

A sweat chloride concentration of ≥60 mmol/L is consistent with cystic fibrosis in an appropriate clinical setting, usually requiring confirmation according to diagnostic protocols.

Values below this threshold require interpretation according to age, symptoms, newborn screening results, and CFTR genetic testing.

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Why Is Sweat Salty?

In normal sweat ducts, CFTR helps reabsorb chloride, with sodium following.

In cystic fibrosis, defective CFTR reduces chloride reabsorption, leaving increased amounts of chloride and sodium in sweat. This explains the characteristically salty sweat of affected patients.

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8. Life Expectancy

The prognosis of cystic fibrosis has improved dramatically.

Older sources described life expectancy as just over 40 years, but this is now outdated in many countries. Improvements in multidisciplinary care, nutritional support, antimicrobial treatment, and particularly CFTR modulator therapy have substantially increased expected survival.

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Respiratory Manifestations

9. Small-Airway Obstruction and Bronchiectasis

Abnormally thick mucus obstructs the small airways and interferes with mucociliary clearance.

Persistent mucus retention promotes recurrent infection and chronic neutrophilic inflammation. Repeated cycles of obstruction → infection → inflammation → airway damage eventually produce bronchiectasis.

Patients commonly develop chronic cough, sputum production, recurrent respiratory infections, breathlessness, and progressive deterioration in pulmonary function.

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10. Respiratory Infection and Colonisation

Patients with CF are susceptible to chronic and recurrent infection with characteristic respiratory organisms.

Important organisms include Staphylococcus aureus, Haemophilus influenzae, Pseudomonas aeruginosa, and Burkholderia cepacia complex.

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Pseudomonas aeruginosa

Pseudomonas aeruginosa becomes particularly important as patients grow older.

Chronic colonisation can produce progressive airway inflammation and declining lung function. The organism may develop a mucoid phenotype, allowing it to persist within the abnormal airway environment and making eradication increasingly difficult.

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Burkholderia cepacia Complex

Burkholderia cepacia complex is especially important because some strains can cause severe respiratory deterioration and are difficult to treat because of antimicrobial resistance.

Cross-infection between patients with CF is also an important infection-control concern.

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11. Treatment of Respiratory Disease

Pulmonary exacerbations are treated with appropriate antibiotics, guided where possible by respiratory cultures and previous microbiological results.

Some patients receive long-term or inhaled antimicrobial therapy to suppress chronic infection.

Management also includes airway-clearance physiotherapy, exercise, mucolytic therapies, and other treatments designed to improve mucus clearance.

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CFTR Modulator Therapy

A major development in modern treatment is the use of CFTR modulators, which target the underlying abnormal CFTR protein rather than simply treating its consequences.

Different combinations are used according to the patient’s specific CFTR genotype, and highly effective modulator therapy has substantially improved lung function and other outcomes in many eligible patients.

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Gastrointestinal Manifestations

12. Pancreatic Insufficiency

Exocrine pancreatic insufficiency occurs in the majority of patients with classic CF.

Thick secretions obstruct the pancreatic ducts, resulting in progressive pancreatic damage and inadequate delivery of digestive enzymes into the intestine.

This causes fat and protein malabsorption, steatorrhoea, poor weight gain, and deficiencies of fat-soluble vitamins A, D, E, and K.

Treatment includes pancreatic enzyme replacement therapy and nutritional supplementation.

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13. Meconium Ileus

Meconium ileus is an important neonatal presentation of cystic fibrosis.

Abnormally thick intestinal contents obstruct the terminal ileum, producing abdominal distension, failure to pass meconium, and intestinal obstruction shortly after birth.

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Distal Intestinal Obstruction Syndrome

Older children and adults with CF can develop distal intestinal obstruction syndrome (DIOS).

Thick intestinal material accumulates, particularly around the terminal ileum and caecum, producing abdominal pain, distension, and partial or complete intestinal obstruction.

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14. Liver Disease

Abnormal CFTR function can produce thickened bile and obstruction of small intrahepatic bile ducts.

Some patients consequently develop CF-associated hepatobiliary disease, which can include focal biliary fibrosis, multilobular cirrhosis, and portal hypertension.

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15. Gallstones

Gallstones occur more frequently in people with CF.

Altered bile composition and gallbladder dysfunction contribute to their development.

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16. Pancreatitis

Recurrent acute or chronic pancreatitis can occur in some individuals with CF, particularly those who retain a degree of pancreatic exocrine function.

Interestingly, patients with severe pancreatic insufficiency may be less likely to develop pancreatitis because extensive pancreatic destruction has already occurred.

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Other Manifestations

17. Cystic Fibrosis-Related Diabetes

Cystic fibrosis-related diabetes (CFRD) becomes increasingly common with age.

Progressive pancreatic damage reduces insulin secretion, while illness-related insulin resistance may contribute. CFRD has features of both type 1 and type 2 diabetes but represents a distinct form of diabetes associated with CF.

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18. Pneumothorax

Advanced bronchiectasis and structural lung disease can predispose patients to spontaneous pneumothorax.

This may present with sudden worsening of breathlessness and pleuritic chest pain and can be particularly serious in patients who already have significantly reduced pulmonary reserve.

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19. Male Infertility

Almost all men with classic cystic fibrosis are infertile, usually because of congenital bilateral absence or severe abnormality of the vas deferens.

Importantly, spermatogenesis may remain intact, so biological fatherhood may sometimes be possible using assisted reproductive techniques.

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20. Female Reproductive Effects

Women with CF are generally capable of becoming pregnant, although fertility may be reduced.

Abnormally thick cervical mucus, nutritional status, and severity of chronic illness can contribute to reduced fertility.

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21. Osteoporosis

Patients with CF have an increased risk of reduced bone mineral density and osteoporosis.

Contributing factors include chronic inflammation, malabsorption of vitamin D, poor nutritional status, reduced physical activity, delayed puberty, and exposure to systemic corticosteroids in some patients.

This increases the risk of vertebral and other fractures.

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Key Clinical Pattern

Think of cystic fibrosis as an autosomal recessive CFTR disorder causing abnormal epithelial ion and water transport and therefore thick, dehydrated secretions.

The classic pattern is chronic/recurrent respiratory infection + bronchiectasis + pancreatic insufficiency and malabsorption + high sweat chloride.

Important organisms include S. aureus, H. influenzae, P. aeruginosa, and B. cepacia complex, while important extrapulmonary complications include meconium ileus/DIOS, CF-related diabetes, hepatobiliary disease, male infertility, and osteoporosis.

Modern CFTR modulator therapy has transformed the outlook for many patients, making the older life-expectancy figures in traditional notes increasingly outdated.

Medicine – Lung Cancer

Lung cancer is one of the most important causes of cancer-related morbidity and mortality. Most cases are strongly associated with tobacco smoking, although occupational exposures, environmental carcinogens, and pre-existing lung disease also contribute. Lung cancers are broadly divided into non-small-cell lung cancer (NSCLC) and small-cell lung cancer (SCLC) because their biological behaviour, staging, treatment, and prognosis differ substantially.

1. Causes and Risk Factors

Cigarette Smoking

Cigarette smoking is the major preventable cause of lung cancer and accounts for the large majority of cases. Risk increases with the duration and intensity of smoking exposure and decreases progressively after smoking cessation.

Older sources sometimes quote smoking as causing approximately 95% of cases, but modern estimates are generally lower and vary by population, sex, and tumour subtype.

Occupational Exposure

Several occupational carcinogens increase the risk of lung cancer. An important example is asbestos exposure, particularly in construction, shipbuilding, insulation work, and other historically exposed industries.

Smoking and asbestos exposure have a synergistic effect, producing a substantially greater risk of lung cancer when both are present.

Environmental Exposure

Environmental factors include passive tobacco smoke and air pollution. Other important environmental or occupational carcinogens include radon, silica, arsenic, chromium, nickel, and diesel exhaust.

Pulmonary Fibrosis

Lung cancer occurs more frequently in patients with certain forms of pulmonary fibrosis, including idiopathic pulmonary fibrosis.

Chronic epithelial injury, inflammation, and abnormal tissue repair are thought to contribute to malignant transformation.

2. Histological Types

Lung cancers are divided into two major categories:

Non-small-cell lung cancer (NSCLC) and small-cell lung cancer (SCLC).

The percentages in older notes have changed considerably over time. In particular, adenocarcinoma is now the most common histological subtype of lung cancer in many populations, rather than squamous cell carcinoma.

Non-Small-Cell Lung Cancer

NSCLC accounts for approximately 85% of lung cancers and includes adenocarcinoma, squamous cell carcinoma, and large-cell carcinoma.

Adenocarcinoma

Adenocarcinoma is now the most common form of lung cancer.

It frequently develops peripherally within the lung and is also the most common major histological subtype encountered in people who have never smoked, although smoking remains an important risk factor.

Modern classification incorporates several adenocarcinoma growth patterns; the older term bronchoalveolar carcinoma has largely been replaced by more specific pathological categories such as adenocarcinoma in situ and lepidic-predominant adenocarcinoma.

Squamous Cell Carcinoma

Squamous cell carcinoma is strongly associated with cigarette smoking and classically arises in the central or proximal airways.

These tumours may undergo central necrosis and cavitation. Squamous carcinoma is also particularly associated with secretion of parathyroid hormone-related peptide (PTHrP), producing paraneoplastic hypercalcaemia.

Large-Cell Carcinoma

Large-cell carcinoma is a poorly differentiated form of NSCLC diagnosed when the tumour lacks the characteristic features of adenocarcinoma, squamous carcinoma, or another defined subtype.

It can occur in either central or peripheral regions of the lung and tends to behave aggressively.

3. Small-Cell Lung Cancer

Small-cell lung cancer accounts for roughly 10–15% of lung cancers and has an exceptionally strong association with cigarette smoking.

It commonly arises centrally, close to the major bronchi, and is characterised by rapid growth, early lymphatic involvement, and early distant metastasis.

Because SCLC is usually already systemic by diagnosis, surgery has only a very limited role. Treatment generally relies on systemic therapy with or without radiotherapy, depending on disease extent and patient factors.

Respiratory Symptoms

4. Cough

A new persistent cough is one of the commonest presentations of lung cancer.

A change in the character or severity of a pre-existing chronic smoker’s cough can also be significant and warrants investigation.

5. Breathlessness

Dyspnoea may result from bronchial obstruction, collapse of part of the lung, pleural effusion, pneumonia distal to an obstructing tumour, lymphatic spread, or extensive tumour burden.

6. Haemoptysis

Haemoptysis is an important warning symptom.

The amount of blood can range from minor streaking of sputum to substantial bleeding. Persistent or unexplained haemoptysis requires investigation, particularly in an older patient or someone with significant smoking exposure.

7. Chest Pain

Chest pain can result from involvement of the pleura, chest wall, ribs, or mediastinal structures.

Persistent or severe pain may indicate locally advanced disease.

Local Complications

8. Pleural Effusion

Lung cancer can produce a pleural effusion through direct pleural involvement, lymphatic obstruction, or other mechanisms.

A malignant pleural effusion generally indicates advanced disease and has major implications for staging and treatment.

9. Superior Vena Cava Obstruction

A centrally located tumour or enlarged mediastinal lymph nodes may compress the superior vena cava (SVC).

Patients may develop facial and neck swelling, distended neck and chest-wall veins, upper-limb swelling, headache, and breathlessness.

SVC obstruction is particularly associated with centrally located thoracic malignancies, including small-cell lung cancer.

10. Recurrent Laryngeal Nerve Palsy

Involvement of the recurrent laryngeal nerve, particularly the left recurrent laryngeal nerve as it passes through the thorax, can produce vocal cord paralysis.

The characteristic clinical presentation is persistent hoarseness.

11. Phrenic Nerve Palsy

Tumour invasion or compression of the phrenic nerve can paralyse the ipsilateral diaphragm.

A chest radiograph may therefore demonstrate an elevated hemidiaphragm.

12. Pericardial Involvement

Direct or metastatic involvement of the pericardium can cause pericarditis or pericardial effusion.

Large malignant pericardial effusions can impair cardiac filling and potentially produce cardiac tamponade.

13. Dysphagia

Dysphagia may develop when a mediastinal tumour or enlarged lymph nodes compress or invade the oesophagus.

This generally suggests significant local or mediastinal disease.

Paraneoplastic and Non-Metastatic Manifestations

Lung cancers can produce systemic manifestations without direct metastatic spread. These paraneoplastic syndromes are particularly characteristic of certain histological subtypes.

14. SIADH

Syndrome of inappropriate antidiuretic hormone secretion (SIADH) is classically associated with small-cell lung cancer.

Excess ADH causes water retention and dilutional hyponatraemia, which may produce confusion, lethargy, seizures, or other neurological manifestations when severe.

15. Ectopic ACTH Production

Small-cell lung cancer can also produce ectopic adrenocorticotropic hormone (ACTH).

This results in Cushing syndrome, potentially causing hypertension, hyperglycaemia, hypokalaemia, muscle weakness, and metabolic alkalosis.

16. Hypercalcaemia

Squamous cell carcinoma is classically associated with hypercalcaemia through secretion of parathyroid hormone-related peptide (PTHrP).

Hypercalcaemia may also result from bone metastases, although this is a metastatic rather than a true paraneoplastic mechanism.

Patients may develop thirst, polyuria, constipation, confusion, weakness, and cardiac rhythm abnormalities.

17. Gynaecomastia

Rare lung cancers can secrete hormones such as human chorionic gonadotropin (hCG), potentially producing gynaecomastia.

Older texts particularly associate this with large-cell carcinoma, although it is an uncommon manifestation.

18. Clubbing

Finger clubbing is particularly associated with non-small-cell lung cancer.

It may occur alone or as part of hypertrophic pulmonary osteoarthropathy.

19. Lambert–Eaton Myasthenic Syndrome

Lambert–Eaton myasthenic syndrome (LEMS) is a characteristic paraneoplastic neurological syndrome associated particularly with small-cell lung cancer.

Autoantibodies interfere with presynaptic voltage-gated calcium channels at the neuromuscular junction, producing proximal muscle weakness, reduced reflexes, and autonomic symptoms.

20. Hypertrophic Pulmonary Osteoarthropathy

Hypertrophic pulmonary osteoarthropathy (HPOA) is associated particularly with lung cancer, most often NSCLC.

It consists of digital clubbing, periostosis of long bones, and painful arthralgia or arthritis.

Patients may complain of painful swollen wrists, ankles, knees, or long bones.

Treatment

21. Surgery

Surgical resection can potentially cure selected patients with early-stage NSCLC.

Procedures may include segmentectomy, lobectomy, or occasionally pneumonectomy. Whether surgery is appropriate depends on TNM stage, tumour location, lymph-node involvement, cardiopulmonary reserve, and overall fitness.

Modern outcomes are substantially better than the historical figures in the supplied notes, particularly for cancers detected at an early stage.

22. Radiotherapy

Radiotherapy may be used with curative intent in selected localised disease when surgery is unsuitable, including stereotactic radiotherapy for some early-stage tumours.

It may also be combined with systemic therapy in locally advanced disease or used palliatively to relieve symptoms such as pain, haemoptysis, or obstruction.

23. Systemic Treatment

Chemotherapy remains important in both NSCLC and SCLC.

Modern NSCLC treatment has expanded considerably beyond conventional chemotherapy. Depending on tumour histology and molecular testing, patients may receive targeted therapy or immunotherapy.

Testing for actionable molecular abnormalities and immune biomarkers is therefore an important part of contemporary management of advanced NSCLC.

Suitability for Surgery

24. Small-Cell Histology

Small-cell lung cancer is generally not treated surgically because of its strong tendency to metastasise early.

Surgery may occasionally be considered in exceptionally early, carefully staged disease, but this represents a small minority of patients.

25. Advanced or Metastatic Disease

Distant metastatic disease generally excludes curative surgical resection of the primary lung tumour.

Extensive mediastinal nodal disease and invasion of unresectable vital structures may also make surgery inappropriate.

26. Malignant Pleural Effusion

A confirmed malignant pleural effusion represents metastatic pleural involvement and generally excludes conventional curative lung resection.

A bloody effusion alone, however, does not automatically prove malignant involvement and requires appropriate investigation.

27. Poor Performance Status and Pulmonary Reserve

Patients must have sufficient general fitness and cardiopulmonary reserve to tolerate lung resection.

Older rules such as an absolute FEV₁ below 1.5 L are no longer used alone to determine operability. Modern assessment uses predicted postoperative lung function, exercise capacity, comorbidities, and the planned extent of resection.

28. Tumour Location

Very central tumours close to the carina or involving major mediastinal structures can make surgical resection technically difficult.

However, the older rule that a tumour less than 1.5 cm from the carina is automatically inoperable is outdated. Modern decisions are based on formal TNM staging, resectability, and multidisciplinary assessment.

Prognosis

29. Small-Cell Lung Cancer

Small-cell lung cancer generally has a poorer prognosis because of its rapid growth and tendency to metastasise early.

Limited-stage disease has a better prognosis than extensive-stage disease, but recurrence after initial treatment remains common.

30. Non-Small-Cell Lung Cancer

The prognosis of NSCLC varies enormously according to stage.

Early localised cancers treated successfully with surgery or stereotactic radiotherapy can have relatively favourable long-term survival, whereas metastatic disease has a much poorer prognosis.

The historical figure of approximately 10% overall five-year survival is therefore outdated. Modern survival has improved because of earlier detection, better staging, improved surgery and radiotherapy, targeted therapies, and immunotherapy.

Key Clinical Pattern

Think of lung cancer in a patient—particularly one with significant smoking exposure—who develops a new or changing cough, haemoptysis, unexplained breathlessness, persistent chest pain, weight loss, or recurrent chest infection.

Remember the classic paraneoplastic associations: small-cell carcinoma → SIADH, ectopic ACTH and Lambert–Eaton syndrome; squamous cell carcinoma → PTHrP-mediated hypercalcaemia; NSCLC → clubbing and hypertrophic pulmonary osteoarthropathy.

The major distinction is between NSCLC, where surgery may be curative in appropriately selected early-stage disease, and SCLC, which usually requires systemic therapy because of its tendency for rapid growth and early metastatic spread.

Medicine – Mesothelioma

Malignant mesothelioma is an aggressive cancer arising from the mesothelial lining of serosal surfaces, most commonly the pleura. Pleural mesothelioma is strongly associated with previous asbestos exposure and typically appears only after a very long latent period.

1. Malignant Tumour of the Pleura

The most common form is malignant pleural mesothelioma, which develops from the mesothelial cells lining the pleural cavity.

The tumour tends to spread diffusely along the pleural surface, causing irregular pleural thickening and encasement of the lung rather than forming a single discrete mass.

2. Association with Asbestos

A large proportion of pleural mesothelioma cases are related to previous asbestos exposure.

Older teaching often quotes a figure of about 85%, although the exact proportion varies between populations and occupational settings.

Unlike lung cancer, the risk of mesothelioma is not substantially increased by cigarette smoking.

3. Occupational and Secondary Exposure

Mesothelioma has historically been most common in men, reflecting greater occupational exposure to asbestos in industries such as shipbuilding, construction, insulation work, mining, and manufacturing.

However, disease can also occur in people with secondary household exposure. A classic example is a family member who repeatedly handled or washed asbestos-contaminated work clothes.

4. Crocidolite Exposure

Among the major asbestos fibre types, crocidolite, or blue asbestos, has traditionally been regarded as one of the most strongly associated with mesothelioma.

Its long, thin fibres can penetrate deeply into the lungs and pleura and remain within tissues for many years.

5. Long Latency Period

Mesothelioma usually develops only after a prolonged interval following asbestos exposure.

The latency period is commonly 20–50 years or longer, which means patients may present decades after the original occupational or environmental exposure has ended.

6. Clinical Presentation

Patients often present with progressive breathlessness, chest pain, weight loss, fatigue, and recurrent pleural effusions.

The pleural effusion is often unilateral, and the expanding pleural tumour can progressively restrict the affected lung.

7. Imaging

Chest radiography may show unilateral pleural effusion, pleural thickening, and reduced volume of the affected hemithorax.

CT is more useful for demonstrating nodular pleural thickening, pleural masses, involvement of the mediastinal pleura, and encasement of the lung.

8. Diagnosis

Definitive diagnosis usually requires tissue biopsy, often obtained thoracoscopically.

Pleural fluid cytology alone may be insufficient because malignant cells are not always detected in the effusion.

9. Prognosis

Malignant mesothelioma generally has a poor prognosis because it is often advanced at the time of diagnosis and tends to spread extensively along the pleural surface.

Treatment may involve combinations of systemic anticancer therapy, radiotherapy, surgery in highly selected patients, and palliative measures such as management of recurrent pleural effusions.

Key Clinical Pattern

Think of malignant pleural mesothelioma in a patient with a history of asbestos exposure decades earlier who presents with progressive breathlessness, chest pain, weight loss, and a recurrent unilateral pleural effusion.

The key association is asbestos exposure with a very long latency period, and crocidolite (blue asbestos) is classically considered particularly carcinogenic.

Medicine – Interstitial Lung Disease (Pulmonary Fibrosis)

Interstitial lung disease (ILD) refers to a broad group of disorders that affect the pulmonary interstitium and may lead to inflammation, scarring, and progressive pulmonary fibrosis. Patients commonly present with progressive exertional breathlessness, dry cough, fine inspiratory crackles, restrictive lung physiology, and reduced gas transfer.

A useful way to remember the differential diagnosis is by the predominant radiological distribution, particularly whether fibrosis mainly affects the upper or lower lobes.

1. Predominantly Upper-Lobe Disease

Upper-lobe or upper-zone predominance is seen in several granulomatous, occupational, infectious, and inflammatory lung disorders.

Sarcoidosis

Sarcoidosis can produce chronic interstitial lung disease with fibrosis, particularly in longstanding pulmonary disease.

The fibrotic changes tend to involve the upper and mid zones and may be associated with hilar or mediastinal lymphadenopathy, traction bronchiectasis, and architectural distortion.

Tuberculosis

Pulmonary tuberculosis, particularly chronic or previously treated disease, can leave residual upper-lobe fibrosis, volume loss, scarring, and cavitation.

The fibrosis often reflects previous destruction of lung tissue rather than a primary diffuse interstitial fibrotic process.

Pneumoconiosis

Several forms of pneumoconiosis can produce upper-zone nodular and fibrotic changes, especially when exposure has been prolonged.

Coal workers’ pneumoconiosis, for example, may progress from small nodular opacities to progressive massive fibrosis, usually affecting the upper lungs.

Silicosis

Silicosis classically produces multiple small nodules predominantly in the upper lobes.

Advanced disease may result in progressive massive fibrosis with large fibrotic masses and severe distortion of normal lung architecture. Hilar lymph nodes may show characteristic eggshell calcification.

Ankylosing Spondylitis

Ankylosing spondylitis can rarely cause upper-lobe pulmonary fibrosis, usually in longstanding disease.

The fibrosis may be associated with apical scarring, volume loss, and occasionally cavitation. These abnormal upper-lobe spaces can predispose to colonisation by organisms such as Aspergillus.

Allergic Bronchopulmonary Aspergillosis

Allergic bronchopulmonary aspergillosis (ABPA) occurs mainly in patients with asthma or cystic fibrosis and is characterised by hypersensitivity to Aspergillus antigens.

It is more typically associated with central bronchiectasis, mucus plugging, and upper-lobe-predominant infiltrates rather than being a classic primary fibrosing ILD. Chronic or severe disease can nevertheless produce bronchiectatic and fibrotic change.

2. Predominantly Lower-Lobe Disease

Lower-zone or basal predominance is particularly characteristic of several fibrotic and connective tissue-related lung diseases.

Bronchiectasis

Bronchiectasis itself is primarily an airway disorder rather than a true interstitial lung disease.

However, chronic lower-lobe bronchiectasis may produce scarring and fibrotic change around damaged airways, especially when associated with recurrent infection.

Asbestosis

Asbestosis is a diffuse interstitial pulmonary fibrosis caused by significant asbestos exposure.

Fibrosis predominantly affects the lower lobes and subpleural regions. Patients may have dry cough, exertional breathlessness, bibasal inspiratory crackles, finger clubbing, restrictive lung function, and reduced gas transfer.

Usual Interstitial Pneumonia

Usual interstitial pneumonia (UIP) is the characteristic radiological and histological pattern associated with idiopathic pulmonary fibrosis when no secondary cause is identified.

It predominantly affects the subpleural and basal regions and is characterised by reticulation, traction bronchiectasis, and honeycombing.

Rheumatoid Arthritis

Rheumatoid arthritis can cause interstitial lung disease, and the UIP pattern is common.

Patients may develop progressive dry cough and exertional breathlessness with bibasal fibrotic changes on imaging. RA can also cause pleural disease, pulmonary nodules, and bronchiectasis.

Systemic Sclerosis

Systemic sclerosis is strongly associated with interstitial lung disease, typically with a lower-lobe and peripheral predominance.

The most common imaging pattern is nonspecific interstitial pneumonia (NSIP), although UIP can also occur. Pulmonary arterial hypertension is another major pulmonary complication of systemic sclerosis.

3. Drug- and Treatment-Induced Interstitial Lung Disease

Several medications and therapeutic interventions can cause inflammatory pneumonitis, pulmonary fibrosis, or both.

Amiodarone

Amiodarone can cause pulmonary toxicity ranging from mild pneumonitis to severe interstitial fibrosis.

Patients may develop progressive dry cough, dyspnoea, diffuse pulmonary infiltrates, restrictive lung function, and impaired gas transfer.

Methotrexate

Methotrexate can cause drug-induced pneumonitis, often presenting with dry cough, fever, breathlessness, and diffuse infiltrates.

This is usually an inflammatory hypersensitivity-type reaction rather than slowly progressive dose-related fibrosis, although distinguishing drug toxicity from underlying rheumatological lung disease can sometimes be difficult.

Nitrofurantoin

Nitrofurantoin can cause both acute and chronic pulmonary reactions.

Acute disease may resemble hypersensitivity pneumonitis, while prolonged exposure can lead to chronic interstitial inflammation and pulmonary fibrosis.

Bleomycin

Bleomycin is a well-known cause of dose-related pulmonary toxicity.

It can produce interstitial pneumonitis followed by progressive pulmonary fibrosis, and the risk increases with greater cumulative exposure and certain additional risk factors.

Radiotherapy

Thoracic radiotherapy can produce lung injury in two main stages.

An earlier radiation pneumonitis may develop within months of treatment, followed later by permanent radiation fibrosis. The abnormalities often correspond geographically to the irradiated portion of lung.

Key Clinical Pattern

For exam purposes, a useful distribution is:

Upper-lobe predominant: sarcoidosis, TB-related scarring, pneumoconiosis, silicosis, ankylosing spondylitis, and chronic ABPA-related change.

Lower-lobe predominant: asbestosis, UIP/IPF, rheumatoid arthritis-associated ILD, and systemic sclerosis-associated ILD.

Important causes of drug- or treatment-induced ILD include amiodarone, methotrexate, nitrofurantoin, bleomycin, and thoracic radiotherapy.

A useful correction is that bronchiectasis and ABPA are primarily airway diseases rather than classic interstitial lung diseases, although both may produce associated fibrosis in chronic disease.

Medicine – Usual Interstitial Pneumonia (UIP) / Cryptogenic Fibrosing Alveolitis

Usual interstitial pneumonia (UIP) is a characteristic pattern of chronic interstitial lung injury associated with progressive pulmonary fibrosis. The older term cryptogenic fibrosing alveolitis (CFA) was historically used for what is now usually called idiopathic pulmonary fibrosis (IPF) when no underlying cause is identified.

UIP is defined mainly by its radiological and histopathological pattern, whereas IPF is the clinical diagnosis made when that UIP pattern occurs without another identifiable cause.

1. Pathology

UIP is characterised by patchy interstitial fibrosis affecting the lung parenchyma, particularly in the subpleural and basal regions.

A key pathological feature is temporal heterogeneity, meaning that different areas of the lung show different stages of disease at the same time.

Alternating Areas of Lung Injury

Microscopically, there may be alternating zones of:

Relatively normal lung,

Active fibroblastic change,

Established fibrosis, and

Honeycomb destruction.

This patchwork appearance helps distinguish UIP from some other interstitial lung diseases that produce a more uniform pattern of inflammation or fibrosis.

2. Epidemiology

UIP/IPF is generally more common in older adults and has historically been reported more frequently in men than women.

It is also strongly associated with a history of cigarette smoking, although smoking is not required for the diagnosis.

3. Dry Cough

A persistent dry, non-productive cough is one of the most common presenting symptoms.

The cough is usually chronic and may become troublesome as fibrosis progresses.

4. Progressive Breathlessness

Patients commonly develop progressive exertional dyspnoea.

Initially, breathlessness may occur only with significant activity, but as lung compliance and gas transfer deteriorate, symptoms may progress to breathlessness during routine activities or even at rest.

5. Finger Clubbing

Digital clubbing is a recognised physical sign in UIP/IPF.

It reflects chronic pulmonary disease and may be present even before very advanced respiratory failure develops.

6. Cyanosis

Cyanosis may occur in advanced disease when gas exchange becomes severely impaired.

It usually reflects significant arterial hypoxaemia and therefore tends to be a later clinical feature.

7. Fine Inspiratory Crepitations

A very characteristic examination finding is fine, late-inspiratory bibasal crackles, often described as “Velcro” crackles.

These result from the sudden opening of small fibrotic airways and alveolar units during inspiration.

Diagnosis

8. Pulmonary Function Tests

Pulmonary function testing typically shows a restrictive pattern.

There is usually a reduction in:

Forced vital capacity (FVC) and

Total lung capacity (TLC).

The FEV1/FVC ratio is usually normal or increased, helping distinguish restriction from obstructive airway disease.

9. Reduced Gas Transfer

Gas transfer is commonly impaired.

The DLCO/TLCO is reduced, often significantly, because fibrosis thickens and disrupts the alveolar-capillary interface.

This contributes to exertional oxygen desaturation.

10. Chest Radiograph

The chest radiograph may show bilateral bibasal interstitial or reticular shadowing.

As the disease advances, lung volumes may become reduced and coarse reticular change may become more obvious.

However, chest radiography is less sensitive and less specific than high-resolution CT.

11. High-Resolution CT

High-resolution CT (HRCT) is the key imaging investigation.

A typical UIP pattern includes:

Subpleural and basal predominance,

Reticular abnormalities,

Honeycombing, and

Traction bronchiectasis or bronchiolectasis.

Marked ground-glass change is usually less prominent than the fibrotic reticular and honeycomb abnormalities.

12. Honeycomb Change

Honeycombing refers to clustered, cystic air spaces caused by severe destruction and remodelling of normal lung architecture.

It is a hallmark of advanced fibrosis and strongly supports the diagnosis of UIP when present in the appropriate distribution.

13. Type I Respiratory Failure

Advanced disease may produce type I respiratory failure, characterised by hypoxaemia without primary hypercapnia.

This occurs because severe fibrosis impairs diffusion and creates ventilation-perfusion mismatch.

Carbon dioxide retention is usually a late feature because patients initially compensate by increasing ventilation.

14. Excluding Secondary Causes

Before diagnosing idiopathic pulmonary fibrosis, other causes of a UIP pattern must be excluded.

These include connective tissue disease, occupational or environmental exposure, certain drugs, and chronic hypersensitivity pneumonitis.

Therefore, a careful clinical history and appropriate autoimmune and exposure assessment are essential.

Key Clinical Pattern

Think of UIP/IPF in an older patient with progressive exertional breathlessness, persistent dry cough, finger clubbing, and fine bibasal late-inspiratory “Velcro” crackles.

The typical investigation pattern is restrictive spirometry, reduced gas transfer, bibasal interstitial shadowing, and HRCT showing basal subpleural reticulation, traction bronchiectasis, and honeycombing.

The most important modern distinction is that UIP is the radiological/pathological pattern, while idiopathic pulmonary fibrosis is the clinical disease diagnosed when UIP occurs without an identifiable underlying cause.

Medicine – Extrinsic Allergic Alveolitis (Hypersensitivity Pneumonitis)

Extrinsic allergic alveolitis (EAA), now more commonly called hypersensitivity pneumonitis (HP), is an immune-mediated inflammatory disease of the lung caused by repeated inhalation of certain environmental antigens. These antigens are usually derived from organic dusts, fungi, bacteria such as thermophilic actinomycetes, or animal proteins.

Unlike asthma, the main inflammatory process occurs in the alveoli and pulmonary interstitium rather than primarily in the bronchi, which explains why breathlessness and cough are prominent while wheezing is usually absent.

1. Pathogenesis

EAA develops when a susceptible individual repeatedly inhales an antigen capable of producing an abnormal immune response within the distal airways and alveoli.

Traditionally, the disease has been described as involving a combination of type III immune-complex hypersensitivity and type IV delayed T-cell-mediated hypersensitivity.

Repeated inflammation produces lymphocytic alveolitis and interstitial inflammation. If exposure continues, chronic inflammation may eventually result in permanent pulmonary fibrosis.

2. Immunological Mechanism

Patients exposed to the responsible antigen may develop circulating IgG antibodies, sometimes called precipitating antibodies or precipitins.

These antibodies indicate sensitisation to the antigen but do not necessarily prove that it is causing the patient’s lung disease. Cellular immunity, particularly involving T lymphocytes, is also central to the development of hypersensitivity pneumonitis.

Important Types of Extrinsic Allergic Alveolitis

3. Farmer’s Lung

Farmer’s lung is a classic form of hypersensitivity pneumonitis caused by exposure to microorganisms growing in mouldy hay and other agricultural material.

Traditional organisms associated with farmer’s lung include the thermophilic actinomycetes Saccharopolyspora rectivirgula (formerly Micropolyspora faeni) and Thermoactinomyces species.

Farmers may inhale large quantities of these antigens while handling damp or mouldy hay, particularly in poorly ventilated environments.

4. Bird-Fancier’s Lung

Bird-fancier’s lung occurs following repeated exposure to avian proteins from birds such as pigeons, budgerigars, parrots, and poultry.

Antigens are present in bird droppings, feathers, and feather bloom, and may become airborne as fine particles that are inhaled deeply into the lungs.

Repeated exposure can produce either episodic acute disease or a more insidious chronic form.

5. Malt Worker’s Lung

Malt worker’s lung is an occupational form of hypersensitivity pneumonitis associated with exposure to fungal antigens during the production and handling of malt.

A classic causative organism is Aspergillus clavatus, which may contaminate barley and malt and release airborne fungal spores.

Clinical Features

6. Acute Disease

In acute hypersensitivity pneumonitis, symptoms characteristically develop several hours after significant antigen exposure, traditionally around 4–9 hours later.

Patients may experience fever, chills or flu-like symptoms, dry cough, chest tightness, malaise, and shortness of breath. Fine inspiratory crackles may be heard on examination.

Absence of Wheeze

Wheezing is usually absent, which can help distinguish EAA from allergic asthma.

In asthma, the predominant problem is reversible bronchial obstruction. In EAA, inflammation predominantly involves the alveoli, small airways, and interstitial tissues.

Resolution After Exposure

A mild acute episode may improve considerably within approximately 24–48 hours after removal from the causative antigen.

However, symptoms can recur each time the individual is re-exposed. Repeated episodes should therefore prompt careful investigation of occupational, domestic, and recreational exposures.

7. Chronic Hypersensitivity Pneumonitis

Repeated or continuous antigen exposure can produce chronic hypersensitivity pneumonitis.

Patients may develop gradually progressive exertional dyspnoea, persistent cough, fatigue, exercise limitation, and weight loss rather than obvious attacks occurring after exposure.

Longstanding inflammation can lead to irreversible pulmonary fibrosis, architectural distortion, traction bronchiectasis, and eventually chronic respiratory impairment.

Diagnosis

8. Chest Imaging

The chest radiograph may be normal, particularly in mild or early disease.

When abnormal, it may demonstrate diffuse or patchy hazy infiltrates and small nodular opacities.

High-resolution CT (HRCT) is considerably more sensitive and may demonstrate ground-glass opacities, centrilobular nodules, mosaic attenuation, air trapping, and—in chronic fibrotic disease—features of pulmonary fibrosis.

9. Pulmonary Function Tests

Pulmonary function testing commonly demonstrates a restrictive ventilatory defect, particularly when significant interstitial disease is present.

Gas transfer may also be impaired, with a reduced DLCO/TLCO. Some patients, particularly those with prominent small-airway involvement, can demonstrate obstructive or mixed abnormalities.

10. Serum Precipitins

Measurement of serum antigen-specific IgG antibodies, traditionally called serum precipitins, can help demonstrate previous exposure and sensitisation to a suspected antigen.

However, a positive result does not prove active hypersensitivity pneumonitis, because healthy exposed individuals may also develop these antibodies. Similarly, a negative test does not completely exclude the disease.

11. Eosinophilia

Peripheral blood eosinophilia is not a typical feature of EAA.

This is useful when distinguishing hypersensitivity pneumonitis from disorders characterised by prominent eosinophilic inflammation, such as eosinophilic pneumonia or eosinophilic granulomatosis with polyangiitis.

12. Bronchoalveolar Lavage

Bronchoalveolar lavage (BAL) commonly demonstrates an increased proportion of lymphocytes, reflecting the lymphocyte-predominant inflammatory response occurring within the lungs.

Older descriptions emphasise a normal or reduced CD4:CD8 ratio. Although this may occur, the CD4:CD8 ratio is variable and is not sufficiently reliable to diagnose or exclude hypersensitivity pneumonitis.

Treatment

13. Avoidance of the Precipitating Antigen

The most important aspect of treatment is identifying and avoiding the responsible antigen.

This may involve modifying working practices, improving ventilation, using appropriate respiratory protection, removing contaminated material, or—in some cases—completely avoiding the occupational or environmental exposure.

Early antigen avoidance can prevent recurrent attacks and reduce the risk of progression to irreversible fibrosis.

14. Corticosteroids

Systemic corticosteroids may be used in patients with significant acute or subacute disease to reduce pulmonary inflammation and accelerate symptomatic improvement.

Steroids do not replace antigen avoidance, which remains the cornerstone of management. Treatment of chronic fibrotic hypersensitivity pneumonitis is more complex because established fibrosis may be irreversible.

Key Clinical Pattern

Think of extrinsic allergic alveolitis/hypersensitivity pneumonitis when a patient develops fever, dry cough and breathlessness several hours after exposure to an organic antigen, particularly when there is no prominent wheeze.

Classic associations include mouldy hay → farmer’s lung, bird proteins → bird-fancier’s lung, and Aspergillus clavatus → malt worker’s lung.

Diagnosis is supported by the exposure history, HRCT findings, restrictive physiology, antigen-specific IgG and BAL lymphocytosis. The most important treatment is avoidance of the causative antigen, with corticosteroids used when clinically appropriate.

1. Pathogenesis EAA develops when a susceptible individual repeatedly inhales an antigen capable of producing an abnormal immune response within the distal airways and alveoli. Traditionally, the disease has been described as involving a combination of type III immune-complex hypersensitivity and type IV delayed T-cell-mediated hypersensitivity. Repeated inflammation produces lymphocytic alveolitis and interstitial inflammation. If exposure continues, chronic inflammation may eventually result in permanent pulmonary fibrosis. 

2. Immunological Mechanism Patients exposed to the responsible antigen may develop circulating IgG antibodies, sometimes called precipitating antibodies or precipitins. These antibodies indicate sensitisation to the antigen but do not necessarily prove that it is causing the patient’s lung disease. Cellular immunity, particularly involving T lymphocytes, is also central to the development of hypersensitivity pneumonitis. 

Important Types of Extrinsic Allergic Alveolitis 3. Farmer’s Lung Farmer’s lung is a classic form of hypersensitivity pneumonitis caused by exposure to microorganisms growing in mouldy hay and other agricultural material. Traditional organisms associated with farmer’s lung include the thermophilic actinomycetes Saccharopolyspora rectivirgula (formerly Micropolyspora faeni) and Thermoactinomyces species. Farmers may inhale large quantities of these antigens while handling damp or mouldy hay, particularly in poorly ventilated environments. 

4. Bird-Fancier’s Lung Bird-fancier’s lung occurs following repeated exposure to avian proteins from birds such as pigeons, budgerigars, parrots, and poultry. Antigens are present in bird droppings, feathers, and feather bloom, and may become airborne as fine particles that are inhaled deeply into the lungs. Repeated exposure can produce either episodic acute disease or a more insidious chronic form. 

5. Malt Worker’s Lung Malt worker’s lung is an occupational form of hypersensitivity pneumonitis associated with exposure to fungal antigens during the production and handling of malt. A classic causative organism is Aspergillus clavatus, which may contaminate barley and malt and release airborne fungal spores. 

Clinical Features 6. Acute Disease In acute hypersensitivity pneumonitis, symptoms characteristically develop several hours after significant antigen exposure, traditionally around 4–9 hours later. Patients may experience fever, chills or flu-like symptoms, dry cough, chest tightness, malaise, and shortness of breath. Fine inspiratory crackles may be heard on examination. 

Absence of Wheeze Wheezing is usually absent, which can help distinguish EAA from allergic asthma. In asthma, the predominant problem is reversible bronchial obstruction. In EAA, inflammation predominantly involves the alveoli, small airways, and interstitial tissues. 

Resolution After Exposure A mild acute episode may improve considerably within approximately 24–48 hours after removal from the causative antigen. However, symptoms can recur each time the individual is re-exposed. Repeated episodes should therefore prompt careful investigation of occupational, domestic, and recreational exposures. 

7. Chronic Hypersensitivity Pneumonitis Repeated or continuous antigen exposure can produce chronic hypersensitivity pneumonitis. Patients may develop gradually progressive exertional dyspnoea, persistent cough, fatigue, exercise limitation, and weight loss rather than obvious attacks occurring after exposure. Longstanding inflammation can lead to irreversible pulmonary fibrosis, architectural distortion, traction bronchiectasis, and eventually chronic respiratory impairment. 

Diagnosis 8. Chest Imaging The chest radiograph may be normal, particularly in mild or early disease. When abnormal, it may demonstrate diffuse or patchy hazy infiltrates and small nodular opacities. High-resolution CT (HRCT) is considerably more sensitive and may demonstrate ground-glass opacities, centrilobular nodules, mosaic attenuation, air trapping, and—in chronic fibrotic disease—features of pulmonary fibrosis. 

9. Pulmonary Function Tests Pulmonary function testing commonly demonstrates a restrictive ventilatory defect, particularly when significant interstitial disease is present. Gas transfer may also be impaired, with a reduced DLCO/TLCO. Some patients, particularly those with prominent small-airway involvement, can demonstrate obstructive or mixed abnormalities. 

10. Serum Precipitins Measurement of serum antigen-specific IgG antibodies, traditionally called serum precipitins, can help demonstrate previous exposure and sensitisation to a suspected antigen. However, a positive result does not prove active hypersensitivity pneumonitis, because healthy exposed individuals may also develop these antibodies. Similarly, a negative test does not completely exclude the disease. 

11. Eosinophilia Peripheral blood eosinophilia is not a typical feature of EAA. This is useful when distinguishing hypersensitivity pneumonitis from disorders characterised by prominent eosinophilic inflammation, such as eosinophilic pneumonia or eosinophilic granulomatosis with polyangiitis. 

12. Bronchoalveolar Lavage Bronchoalveolar lavage (BAL) commonly demonstrates an increased proportion of lymphocytes, reflecting the lymphocyte-predominant inflammatory response occurring within the lungs. Older descriptions emphasise a normal or reduced CD4:CD8 ratio. Although this may occur, the CD4:CD8 ratio is variable and is not sufficiently reliable to diagnose or exclude hypersensitivity pneumonitis. 

Treatment 13. Avoidance of the Precipitating Antigen The most important aspect of treatment is identifying and avoiding the responsible antigen. This may involve modifying working practices, improving ventilation, using appropriate respiratory protection, removing contaminated material, or—in some cases—completely avoiding the occupational or environmental exposure. Early antigen avoidance can prevent recurrent attacks and reduce the risk of progression to irreversible fibrosis. 

14. Corticosteroids Systemic corticosteroids may be used in patients with significant acute or subacute disease to reduce pulmonary inflammation and accelerate symptomatic improvement. Steroids do not replace antigen avoidance, which remains the cornerstone of management. Treatment of chronic fibrotic hypersensitivity pneumonitis is more complex because established fibrosis may be irreversible. 

Key Clinical Pattern Think of extrinsic allergic alveolitis/hypersensitivity pneumonitis when a patient develops fever, dry cough and breathlessness several hours after exposure to an organic antigen, particularly when there is no prominent wheeze. Classic associations include mouldy hay → farmer’s lung, bird proteins → bird-fancier’s lung, and Aspergillus clavatus → malt worker’s lung. Diagnosis is supported by the exposure history, HRCT findings, restrictive physiology, antigen-specific IgG and BAL lymphocytosis. The most important treatment is avoidance of the causative antigen, with corticosteroids used when clinically appropriate.

Medicine – Occupational Lung Diseases: Coal Workers’ Pneumoconiosis and Silicosis

Occupational lung diseases develop following repeated inhalation of harmful dusts, particles, or chemicals in the workplace. Two important examples are coal workers’ pneumoconiosis (CWP) and silicosis. Both can cause chronic pulmonary inflammation and fibrosis, but they differ in their occupational exposures, radiological distribution, complications, and clinical course.

Coal Workers’ Pneumoconiosis (CWP)

Coal workers’ pneumoconiosis is a chronic occupational lung disease caused by prolonged inhalation of coal mine dust. It occurs predominantly in coal miners and other workers with substantial exposure to respirable coal dust.

Disease severity ranges from relatively mild simple CWP to severe progressive massive fibrosis (PMF).

1. Pathogenesis

During prolonged exposure, very small coal-dust particles are inhaled deeply into the respiratory tract and deposited within the alveoli and respiratory bronchioles.

Alveolar macrophages engulf these particles, but persistent dust accumulation stimulates chronic inflammation and tissue injury. Over time, this can lead to the formation of coal macules, nodules, and pulmonary fibrosis.

2. Simple Coal Workers’ Pneumoconiosis

The early or uncomplicated form is known as simple CWP. Many patients with simple disease have few or no respiratory symptoms.

Chest imaging typically demonstrates multiple small, rounded pulmonary opacities or nodules, often with an upper-lung predominance.

3. Progressive Massive Fibrosis

Simple CWP can progress in some individuals to progressive massive fibrosis (PMF), also called complicated pneumoconiosis.

In PMF, smaller pneumoconiotic nodules merge to form large fibrotic masses, usually in the upper portions of the lungs. This produces significant distortion of normal lung architecture and can result in progressive breathlessness, cough, hypoxaemia, and respiratory impairment.

4. Pulmonary Function Tests

Pulmonary function abnormalities vary according to the extent of disease and the presence of associated airway disease.

A mixed obstructive and restrictive pattern may occur. Obstruction can result from associated chronic airflow limitation, while extensive fibrosis and PMF contribute to restrictive physiology.

5. Occupational Compensation

CWP is a recognised occupational disease, and affected workers may qualify for compensation depending on the diagnostic criteria and legislation of the relevant country.

Older schemes sometimes required characteristic chest radiographic abnormalities for compensation. However, eligibility criteria are jurisdiction-specific and should not be considered a universal medical diagnostic criterion.

Caplan’s Syndrome

Caplan’s syndrome, also known as rheumatoid pneumoconiosis, describes the occurrence of characteristic pulmonary nodules in a patient with rheumatoid arthritis and occupational dust exposure, classically coal dust or silica.

Clinical and Radiological Features

Patients develop multiple, well-defined pulmonary nodules, often appearing relatively rapidly.

The nodules may vary considerably in size and can occasionally undergo central necrosis or cavitation.

Therefore, the classic association to remember is:

Rheumatoid arthritis + pneumoconiosis + multiple pulmonary nodules = Caplan’s syndrome.

Silicosis

Silicosis is an occupational lung disease caused by inhalation of respirable crystalline silica (silicon dioxide). The inhaled particles trigger inflammation and fibrosis within the lungs.

Silicosis may occur as chronic, accelerated, or acute disease, depending largely on the intensity and duration of silica exposure.

1. Occupational Exposure

Workers at risk include those involved in mining, quarrying, stone cutting, tunnelling, foundry work, construction, and abrasive sandblasting.

Modern high-risk exposures can also occur during cutting or fabrication of engineered stone, which may contain a very high concentration of crystalline silica.

2. Acute and Accelerated Disease

Very intense exposure to silica can produce disease much more rapidly than conventional chronic silicosis.

Acute silicosis can develop within months to a few years following extremely heavy exposure and may cause rapidly progressive dyspnoea, dry cough, fatigue, and hypoxaemia.

Accelerated silicosis develops after a shorter period of substantial exposure than chronic silicosis and can progress relatively rapidly to pulmonary fibrosis.

3. Chronic Silicosis

Classic chronic silicosis usually develops after many years of occupational exposure.

The disease is characterised by the formation of multiple small pulmonary nodules, predominantly affecting the upper lobes. These nodules may gradually enlarge and coalesce.

4. Radiological Features

Chest imaging typically demonstrates multiple small, rounded upper-zone nodules.

Hilar and mediastinal lymph nodes may also become enlarged and calcified. A characteristic finding is “eggshell” calcification, in which a thin rim of calcium forms around the periphery of a lymph node.

Advanced silicosis may progress to progressive massive fibrosis, producing large fibrotic upper-lobe masses and severe architectural distortion.

5. Pulmonary Function

Pulmonary function may initially remain relatively preserved. With advanced fibrosis, a restrictive ventilatory defect can develop.

Some patients demonstrate obstructive or mixed abnormalities, particularly when other occupational exposures or smoking-related lung disease coexist.

6. Association with Tuberculosis

An especially important complication of silicosis is an increased susceptibility to tuberculosis.

Silica impairs macrophage function and reduces the ability of the lungs to contain Mycobacterium tuberculosis. Consequently, a patient with silicosis who develops constitutional symptoms, new pulmonary infiltrates, or cavitation should be investigated carefully for active TB.

Key Clinical Differences

Coal workers’ pneumoconiosis results from prolonged coal-dust exposure and produces small pulmonary opacities that may progress to progressive massive fibrosis. The combination of pneumoconiosis, rheumatoid arthritis, and multiple pulmonary nodules is known as Caplan’s syndrome.

Silicosis results from inhalation of crystalline silica, particularly during mining, quarrying, stone cutting, and sandblasting. It characteristically produces upper-lobe nodules, may cause eggshell calcification of hilar lymph nodes, and can progress to massive fibrosis. A particularly important association is the substantially increased risk of tuberculosis.

Medicine – Diseases Caused by Exposure to Asbestos

Asbestos exposure can produce several important pleural and pulmonary diseases. The main conditions are pleural plaques and diffuse pleural thickening, asbestosis, lung cancer, and malignant mesothelioma. These disorders usually have a long latency period, often developing 20 years or more after exposure.

1. Pleural Plaques and Pleural Thickening

Pleural plaques are the most common manifestation of previous asbestos exposure. They usually develop more than 20 years after exposure and are typically found on the parietal pleura, especially along the posterolateral chest wall and over the diaphragm.

They may become calcified and are often detected incidentally on chest radiography or CT.

Clinical Features

Pleural plaques are usually asymptomatic and generally do not cause major respiratory impairment.

However, some patients develop diffuse pleural thickening, in which the pleural fibrosis becomes more extensive and confluent. This can restrict expansion of the lungs and lead to exertional shortness of breath.

Lung Function

Diffuse pleural thickening may produce a restrictive ventilatory defect on spirometry.

The KCO, or carbon monoxide transfer coefficient, may remain relatively normal because the underlying alveolar-capillary membrane may be preserved. This helps distinguish pleural restriction from true interstitial pulmonary fibrosis.

2. Asbestosis

Asbestosis is a form of diffuse interstitial pulmonary fibrosis caused by substantial inhalational exposure to asbestos fibres. It also typically develops only after a long latent period, commonly more than 20 years after exposure.

The fibrosis predominantly affects the lower lobes and subpleural regions of the lungs.

Clinical Features

Patients usually present with a progressive dry cough and exertional dyspnoea.

On examination, fine bibasal or lower-zone inspiratory crepitations are common. Finger clubbing may also occur, particularly in more advanced disease.

Symptoms and functional limitation generally progress gradually.

Association with Lung Cancer

Asbestos exposure significantly increases the risk of bronchogenic carcinoma.

The risk is especially high in individuals who also smoke because smoking and asbestos exposure have a synergistic effect on lung cancer risk.

This is an important distinction from mesothelioma, for which smoking is not considered a major independent risk factor.

Chest Radiograph

The chest radiograph may show bilateral irregular reticular or linear shadowing, particularly in the lower zones.

As disease progresses, more extensive fibrotic changes may appear. Advanced fibrosis can produce architectural distortion, traction bronchiectasis, and honeycomb-type change.

High-resolution CT is more sensitive than a plain chest radiograph for detecting early asbestosis.

Pulmonary Function Tests

Asbestosis produces a restrictive pattern, with reduced lung volumes.

Unlike isolated pleural thickening, the KCO or gas transfer capacity is often reduced because fibrosis damages the alveolar-capillary interface and impairs diffusion of oxygen and carbon monoxide.

Compensation and Occupational Disease

Asbestosis is an important occupational lung disease, and affected individuals may be eligible for occupational disease compensation depending on the jurisdiction, degree of exposure, and severity of impairment.

A detailed occupational history is therefore important in anyone with suspected asbestos-related disease.

3. Malignant Mesothelioma

Malignant mesothelioma is an aggressive tumour arising from mesothelial surfaces, most commonly the pleura.

The majority of cases are associated with previous asbestos exposure, although older figures such as 85% vary between populations and studies. The latency period is often very long, frequently several decades after exposure.

Clinical Features

Patients commonly present with progressive shortness of breath, chest pain, weight loss, and recurrent unilateral pleural effusions.

As the tumour spreads along the pleural surface, it can cause diffuse pleural thickening and encasement of the lung, leading to increasing respiratory restriction.

Imaging

Chest imaging may demonstrate unilateral pleural effusion, nodular pleural thickening, pleural masses, and contraction of the affected hemithorax.

CT is more useful than plain radiography for assessing the extent of pleural disease and planning biopsy.

Key Clinical Pattern

Asbestos exposure causes several characteristic diseases. Pleural plaques are usually asymptomatic markers of previous exposure, while diffuse pleural thickening can cause restrictive breathlessness.

Asbestosis is a lower-zone interstitial pulmonary fibrosis associated with dry cough, exertional dyspnoea, bibasal crackles, clubbing, restrictive lung function, and reduced gas transfer.

Asbestos exposure also increases the risk of lung cancer and malignant mesothelioma, both of which may appear decades after the original occupational or environmental exposure.

1. Pleural Plaques and Pleural Thickening Pleural plaques are the most common manifestation of previous asbestos exposure. They usually develop more than 20 years after exposure and are typically found on the parietal pleura, especially along the posterolateral chest wall and over the diaphragm. They may become calcified and are often detected incidentally on chest radiography or CT. 

Clinical Features Pleural plaques are usually asymptomatic and generally do not cause major respiratory impairment. However, some patients develop diffuse pleural thickening, in which the pleural fibrosis becomes more extensive and confluent. This can restrict expansion of the lungs and lead to exertional shortness of breath. 

Lung Function Diffuse pleural thickening may produce a restrictive ventilatory defect on spirometry. The KCO, or carbon monoxide transfer coefficient, may remain relatively normal because the underlying alveolar-capillary membrane may be preserved. This helps distinguish pleural restriction from true interstitial pulmonary fibrosis. 

2. Asbestosis Asbestosis is a form of diffuse interstitial pulmonary fibrosis caused by substantial inhalational exposure to asbestos fibres. It also typically develops only after a long latent period, commonly more than 20 years after exposure. The fibrosis predominantly affects the lower lobes and subpleural regions of the lungs. 

Clinical Features Patients usually present with a progressive dry cough and exertional dyspnoea. On examination, fine bibasal or lower-zone inspiratory crepitations are common. Finger clubbing may also occur, particularly in more advanced disease. Symptoms and functional limitation generally progress gradually. 

Association with Lung Cancer Asbestos exposure significantly increases the risk of bronchogenic carcinoma. The risk is especially high in individuals who also smoke because smoking and asbestos exposure have a synergistic effect on lung cancer risk. This is an important distinction from mesothelioma, for which smoking is not considered a major independent risk factor. 

Chest Radiograph The chest radiograph may show bilateral irregular reticular or linear shadowing, particularly in the lower zones. As disease progresses, more extensive fibrotic changes may appear. Advanced fibrosis can produce architectural distortion, traction bronchiectasis, and honeycomb-type change. High-resolution CT is more sensitive than a plain chest radiograph for detecting early asbestosis. 

Pulmonary Function Tests Asbestosis produces a restrictive pattern, with reduced lung volumes. Unlike isolated pleural thickening, the KCO or gas transfer capacity is often reduced because fibrosis damages the alveolar-capillary interface and impairs diffusion of oxygen and carbon monoxide. 

Compensation and Occupational Disease Asbestosis is an important occupational lung disease, and affected individuals may be eligible for occupational disease compensation depending on the jurisdiction, degree of exposure, and severity of impairment. A detailed occupational history is therefore important in anyone with suspected asbestos-related disease. 

3. Malignant Mesothelioma Malignant mesothelioma is an aggressive tumour arising from mesothelial surfaces, most commonly the pleura. The majority of cases are associated with previous asbestos exposure, although older figures such as 85% vary between populations and studies. The latency period is often very long, frequently several decades after exposure. 

Clinical Features Patients commonly present with progressive shortness of breath, chest pain, weight loss, and recurrent unilateral pleural effusions. As the tumour spreads along the pleural surface, it can cause diffuse pleural thickening and encasement of the lung, leading to increasing respiratory restriction. 

Imaging Chest imaging may demonstrate unilateral pleural effusion, nodular pleural thickening, pleural masses, and contraction of the affected hemithorax. CT is more useful than plain radiography for assessing the extent of pleural disease and planning biopsy. 

Key Clinical Pattern Asbestos exposure causes several characteristic diseases. Pleural plaques are usually asymptomatic markers of previous exposure, while diffuse pleural thickening can cause restrictive breathlessness. Asbestosis is a lower-zone interstitial pulmonary fibrosis associated with dry cough, exertional dyspnoea, bibasal crackles, clubbing, restrictive lung function, and reduced gas transfer. Asbestos exposure also increases the risk of lung cancer and malignant mesothelioma, both of which may appear decades after the original occupational or environmental exposure.

Medicine – Granulomatous Lung Disease: Sarcoidosis

Sarcoidosis is a systemic granulomatous inflammatory disease that can involve almost any organ, although the lungs and intrathoracic lymph nodes are most commonly affected. Its pathological hallmark is the formation of non-caseating granulomas. The clinical course is highly variable: some patients remain completely asymptomatic and undergo spontaneous resolution, whereas others develop chronic progressive disease with irreversible organ damage.

1. Multisystem Disease

Sarcoidosis is a multisystem disorder, meaning that several organs may be affected simultaneously. Pulmonary involvement is particularly common, but disease can also occur in the skin, eyes, heart, liver, spleen, nervous system, bones, and joints.

The extent of organ involvement varies considerably between patients, making sarcoidosis a disease with a broad range of clinical presentations.

2. Cause

The precise cause of sarcoidosis remains unknown. It is thought to result from an exaggerated immune response to one or more unidentified environmental or infectious antigens in genetically susceptible individuals.

The immune response leads to accumulation of activated T lymphocytes and macrophages and ultimately to the formation of granulomas within affected tissues.

3. Age Distribution

Sarcoidosis commonly affects young and middle-aged adults, although it can occur at virtually any age.

Many patients develop the disease between approximately 20 and 40 years of age, with demographic patterns varying between populations.

4. Ethnic and Geographic Variation

The incidence and clinical severity of sarcoidosis vary considerably according to ethnicity and geographic region.

Older teaching commonly describes sarcoidosis as approximately three times more common in Black populations than White populations, particularly based on US data. More broadly, modern epidemiological studies confirm a substantially increased incidence in some populations of African ancestry, although the exact magnitude varies by location and population studied.

5. Non-Caseating Granulomas

The characteristic pathological lesion of sarcoidosis is the non-caseating granuloma. These granulomas consist predominantly of organised collections of epithelioid macrophages and multinucleated giant cells surrounded by lymphocytes.

Unlike the granulomas classically associated with tuberculosis, sarcoid granulomas usually lack central caseous necrosis.

However, finding a non-caseating granuloma is not by itself diagnostic of sarcoidosis. Other causes of granulomatous inflammation, particularly tuberculosis, fungal infection, occupational exposure, and certain drug reactions, must be excluded according to the clinical setting.

6. Genetic Associations

Sarcoidosis has a genetic component, with particular HLA alleles associated with susceptibility, clinical phenotype, and prognosis.

Older descriptions emphasised associations with HLA-A1, HLA-B8, and HLA-DR3. Modern genetic studies show that the relationship is more complex, with several HLA class II variants associated with different forms and outcomes of the disease.

Pulmonary Manifestations

7. Clinical Features

Pulmonary sarcoidosis has a highly variable presentation. Some patients have no respiratory symptoms and are diagnosed incidentally after an abnormal chest radiograph performed for another reason.

Other patients develop persistent dry cough, exertional shortness of breath, chest discomfort, fever, fatigue, and weight loss.

Respiratory Examination

Physical examination can be surprisingly normal despite significant radiological abnormalities.

Inspiratory crackles may occur when there is substantial interstitial lung involvement. Finger clubbing is uncommon in sarcoidosis; its presence should suggest advanced fibrotic disease or prompt consideration of an alternative diagnosis.

Bilateral Hilar Lymphadenopathy

Bilateral hilar lymphadenopathy (BHL) is one of the most characteristic radiological manifestations of sarcoidosis.

The combination of bilateral hilar lymphadenopathy and erythema nodosum, particularly in a young adult with compatible symptoms, is highly suggestive of sarcoidosis and may form part of the acute presentation known as Löfgren syndrome.

Pulmonary Fibrosis

Most patients do not progress to severe fibrosis, but chronic pulmonary sarcoidosis can eventually produce irreversible pulmonary fibrosis.

Fibrotic disease classically has an upper- and mid-zone predominance, unlike some other fibrotic interstitial lung diseases that predominantly affect the lung bases. Advanced disease can produce architectural distortion, traction bronchiectasis, respiratory impairment, and pulmonary hypertension.

Diagnosis

8. Establishing the Diagnosis

Diagnosis is based on a combination of a compatible clinical and radiological presentation, histological demonstration of non-necrotising granulomatous inflammation when required, and exclusion of alternative causes of granulomatous disease.

No single blood test is sufficiently specific to establish the diagnosis.

Tissue Biopsy

When histological confirmation is required, tissue should ideally be obtained from the safest and most accessible affected site.

Bronchoscopy may be used to obtain transbronchial lung biopsies. In patients with enlarged hilar or mediastinal lymph nodes, endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) is also widely used.

Biopsy typically demonstrates non-caseating granulomas, but infectious causes such as tuberculosis must be excluded before attributing the findings to sarcoidosis.

Hypercalcaemia

Sarcoidosis may cause hypercalcaemia and/or hypercalciuria. Activated macrophages within granulomas can increase production of active vitamin D, resulting in increased intestinal calcium absorption.

Persistent abnormalities of calcium metabolism may contribute to renal calculi and renal impairment.

Serum ACE

Serum angiotensin-converting enzyme (ACE) levels may be elevated because ACE can be produced by cells within sarcoid granulomas.

However, serum ACE has limited sensitivity and specificity and cannot reliably confirm or exclude sarcoidosis. It should therefore be interpreted only as a supportive finding in the appropriate clinical context.

Chest Radiograph Staging

Stage 0 – Normal Chest Radiograph

In Stage 0, the chest radiograph is normal despite the possibility of sarcoidosis involving extrapulmonary organs.

Stage I – Bilateral Hilar Lymphadenopathy

Stage I consists of bilateral hilar lymphadenopathy without pulmonary infiltrates. This pattern is commonly associated with a favourable prognosis and spontaneous resolution.

Stage II – BHL with Pulmonary Infiltrates

Stage II consists of bilateral hilar lymphadenopathy together with pulmonary parenchymal infiltrates.

Both the intrathoracic lymph nodes and lung tissue are therefore visibly involved.

Stage III – Pulmonary Infiltrates Without BHL

Stage III is characterised by pulmonary infiltrates without bilateral hilar lymphadenopathy.

This represents more prominent parenchymal pulmonary involvement.

Stage IV – Pulmonary Fibrosis

An important addition to the older classification in your notes is Stage IV, which represents established pulmonary fibrosis.

There may be upper-lobe volume loss, architectural distortion, fibrotic bands, traction bronchiectasis, and other features of chronic irreversible lung disease.

Extrapulmonary Manifestations

9. Liver

Hepatic involvement is relatively common and is frequently asymptomatic. Granulomas may be found within the liver even when there is little or no clinically apparent hepatic disease.

Some patients develop abnormal liver function tests, hepatomegaly, or, rarely, clinically significant chronic liver disease.

10. Cardiac Sarcoidosis

Cardiac involvement is particularly important because it can produce serious or potentially life-threatening complications.

Granulomatous inflammation and subsequent fibrosis can interfere with the cardiac conduction system and myocardium, producing atrioventricular block, ventricular arrhythmias, cardiomyopathy, heart failure, or sudden cardiac death.

The frequency of clinically apparent cardiac sarcoidosis is considerably lower than some older quoted figures of 30–70%, although occult cardiac involvement may be detected more frequently at imaging or autopsy.

11. Skin

Approximately one-quarter of patients may develop cutaneous manifestations.

Erythema nodosum produces painful, tender red nodules, typically over the shins, and is particularly associated with acute sarcoidosis.

Other manifestations include papules, plaques, subcutaneous nodules, and lupus pernio. Lupus pernio consists of chronic violaceous lesions, particularly affecting the nose, cheeks, ears, and other facial areas, and tends to be associated with more chronic disease.

12. Eyes

Ocular involvement most commonly presents as uveitis, particularly anterior uveitis.

Patients may develop eye pain, redness, photophobia, and visual disturbance. Because untreated ocular inflammation can threaten vision, ophthalmological assessment is important when eye involvement is suspected.

13. Splenic Involvement

The spleen may be infiltrated by granulomas, resulting in splenomegaly.

Significant splenic involvement can occasionally contribute to cytopenias through hypersplenism.

14. Neurological Sarcoidosis

Neurosarcoidosis occurs in a minority of patients but can affect almost any part of the nervous system.

Manifestations include cranial nerve palsies, meningitis, hydrocephalus, hypothalamic or pituitary disease, peripheral neuropathy, spinal cord involvement, and mass-like intracranial lesions.

Cranial neuropathy, particularly facial nerve palsy, is a well-recognised presentation.

15. Bone and Joint Disease

Sarcoidosis may involve the bones and joints. Chronic osseous sarcoidosis can produce cystic or lytic lesions, particularly in the small bones of the hands and feet.

Musculoskeletal disease may also present with arthralgia or inflammatory arthritis, with ankle involvement being particularly characteristic of acute sarcoidosis.

Löfgren Syndrome

Löfgren syndrome is an acute and characteristic presentation of sarcoidosis. It classically consists of the triad of:

Bilateral hilar lymphadenopathy + erythema nodosum + acute arthritis or periarthritis, particularly affecting the ankles.

It usually has a favourable prognosis, and spontaneous resolution is common.

Treatment

16. Observation and Symptomatic Treatment

Not every patient with sarcoidosis requires specific treatment. Patients with mild or asymptomatic disease and preserved organ function may be monitored because spontaneous remission is common.

Symptomatic treatment can be provided when necessary, together with regular assessment for progression or important organ involvement.

17. Corticosteroids

Systemic corticosteroids are a mainstay of treatment when sarcoidosis causes significant symptoms, progressive pulmonary disease, or clinically important extrapulmonary organ involvement.

Treatment is particularly important when there is potentially serious involvement of organs such as the heart, nervous system, or eyes, although management depends on the specific manifestation.

18. Immunosuppressive Therapy

When corticosteroids are ineffective, cause unacceptable adverse effects, or prolonged steroid-sparing treatment is required, additional immunosuppressive therapy may be used.

Methotrexate is a commonly used steroid-sparing agent. Other therapies may include azathioprine, mycophenolate, or selected biologic agents such as anti-TNF therapy in difficult refractory disease.

Key Clinical Pattern

Think of sarcoidosis in a young or middle-aged adult presenting with bilateral hilar lymphadenopathy, dry cough or dyspnoea, erythema nodosum, uveitis, or ankle arthritis.

The pathological hallmark is a non-caseating granuloma, but other granulomatous diseases—especially tuberculosis and fungal infection—must be excluded.

A particularly memorable presentation is Löfgren syndrome: bilateral hilar lymphadenopathy + erythema nodosum + acute ankle arthritis/periarthritis. Pulmonary disease may resolve spontaneously, but a minority of patients develop chronic disease and irreversible pulmonary fibrosis.

Medicine – Connective Tissue Disease and the Lung

Connective tissue diseases (CTDs) frequently involve the respiratory system. Pulmonary manifestations may affect the lung parenchyma, pleura, airways, pulmonary vasculature, or respiratory muscles. In some patients, lung disease may become a major cause of morbidity and can occasionally precede the more typical systemic manifestations of the underlying connective tissue disorder.

1. Rheumatoid Arthritis

Rheumatoid arthritis (RA) can produce several different pulmonary manifestations. Lung involvement is particularly important in patients with longstanding or seropositive disease and may involve the lung parenchyma, pleura, or airways.

Pulmonary Nodules

Rheumatoid nodules can develop within the lungs, particularly in patients with severe seropositive RA. They are usually located peripherally and may be single or multiple.

Some rheumatoid nodules undergo central necrosis and cavitation, which can make them difficult to distinguish radiologically from infection, malignancy, or other causes of cavitating pulmonary nodules.

Pulmonary Fibrosis

Interstitial lung disease (ILD) is one of the most important pulmonary complications of RA. Progressive inflammation and fibrosis of the pulmonary interstitium can produce exertional breathlessness, persistent dry cough, and reduced exercise tolerance.

High-resolution CT may demonstrate several patterns, with usual interstitial pneumonia (UIP) and nonspecific interstitial pneumonia being important examples.

Bronchiectasis

Bronchiectasis occurs more frequently in patients with RA than in the general population. Permanent dilatation of the bronchi can result in chronic productive cough, recurrent respiratory infections, and haemoptysis.

Its presence is particularly important when immunosuppressive treatment is being considered because recurrent pulmonary infection may complicate therapy.

Caplan’s Syndrome

Caplan’s syndrome, also known as rheumatoid pneumoconiosis, occurs when rheumatoid arthritis is associated with occupational exposure to mineral dust, classically coal or silica.

Chest imaging typically demonstrates multiple, well-defined pulmonary nodules, which may enlarge or occasionally cavitate.

Pleural Effusion

RA can cause pleuritis with pleural effusion. The effusion is usually exudative and characteristically may have a very low glucose concentration and low pH.

Patients may experience pleuritic chest pain and breathlessness, although some rheumatoid pleural effusions are discovered incidentally.

2. Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) can affect several components of the respiratory system. Although pulmonary fibrosis and shrinking lung syndrome are recognised manifestations, SLE can also cause pleuritis, pleural effusions, acute lupus pneumonitis, and pulmonary haemorrhage.

Pulmonary Fibrosis

Chronic interstitial lung disease and pulmonary fibrosis can occur in SLE, although clinically significant fibrosis is less characteristic than in systemic sclerosis.

Patients may develop progressive exertional dyspnoea, dry cough, restrictive pulmonary function abnormalities, and impaired gas transfer.

Shrinking Lung Syndrome

Shrinking lung syndrome is a rare but distinctive pulmonary complication of SLE. It is characterised by progressive breathlessness, reduced lung volumes, and elevation of the diaphragm without significant interstitial lung disease explaining the restriction.

The mechanism is not completely understood but may involve diaphragmatic dysfunction, pleural inflammation, and abnormalities of respiratory muscle function.

3. Systemic Sclerosis

Systemic sclerosis (scleroderma) has a particularly strong association with pulmonary disease. Lung involvement is clinically important because it is a major contributor to morbidity and mortality.

The two major pulmonary complications to remember are interstitial lung disease and pulmonary arterial hypertension.

Pulmonary Fibrosis

Interstitial lung disease with pulmonary fibrosis is a major manifestation of systemic sclerosis. The most common radiological pattern is nonspecific interstitial pneumonia (NSIP).

Progressive fibrosis causes exertional dyspnoea, dry cough, restrictive lung physiology, and reduced diffusing capacity. High-resolution CT and pulmonary function tests are important for assessment and monitoring.

Bronchiectasis

Bronchiectatic changes may occur in systemic sclerosis, particularly as traction bronchiectasis secondary to pulmonary fibrosis. As fibrotic lung tissue contracts, it pulls the airways open and produces abnormal bronchial dilatation.

This differs from primary bronchiectasis caused mainly by recurrent airway infection.

Pulmonary Arterial Hypertension

An additional important manifestation is pulmonary arterial hypertension (PAH), particularly associated with limited cutaneous systemic sclerosis.

Patients may develop progressive exertional breathlessness, fatigue, syncope, and eventually right-sided heart failure. Pulmonary hypertension can occur independently of significant pulmonary fibrosis and therefore requires specific consideration during follow-up.

Key Clinical Pattern

Rheumatoid arthritis is associated with pulmonary nodules, interstitial fibrosis, bronchiectasis, Caplan’s syndrome, and pleural disease.

SLE can cause interstitial lung disease and shrinking lung syndrome, as well as pleuritis, pneumonitis, and pulmonary haemorrhage.

Systemic sclerosis is particularly associated with interstitial pulmonary fibrosis and pulmonary arterial hypertension, while bronchiectatic changes may develop secondary to fibrosis.