Caplan Syndrome

Caplan syndrome (rheumatoid pneumoconiosis) is the occurrence of multiple well defined pulmonary rheumatoid nodules in patients with rheumatoid arthritis exposed to dust, classically coal, silica and asbestos.

• Described in coal miners; now rare.

• Nodules 0.5 to 5 cm appear rapidly, peripherally in the lung, sometimes before arthritis.

• Pathology: necrotic centre with dust ring, surrounded by palisading histiocytes.

• Nodules may cavitate, calcify, or remain stable for years.

• Often asymptomatic, found incidentally on imaging.

• Cough, dyspnoea, haemoptysis, pleuritic pain if cavitation or pneumothorax.

• Rheumatoid arthritis, subcutaneous nodules, rheumatoid factor positivity.

• Lung function usually normal or mildly impaired.

• Chest radiograph and CT: multiple well defined peripheral round nodules (0.5 to 5 cm) on a background of mild or no pneumoconiosis.

• Rheumatoid factor and anti-CCP positive in most.

• Exclude tuberculosis (sputum, IGRA), malignancy, fungal infection, metastases, granulomatosis with polyangiitis. Biopsy or PET CT when nodules grow or suspicious.

• Exposure history and spirometry.

• Remove from dust exposure; smoking cessation.

• No specific therapy for nodules; treat rheumatoid arthritis (methotrexate, biologics) with attention to pulmonary monitoring.

• Screen for and treat tuberculosis in silica exposure: latent infection, isoniazid 300 mg daily plus pyridoxine 25 mg for 6 months, or rifampicin 600 mg for 4 months.

• Serial imaging every 6 to 12 months; biopsy for enlarging or atypical nodules to exclude malignancy.

• Treat complications: cavity infection with antibiotics, pneumothorax with drainage, haemoptysis with tranexamic acid 1 g three times daily.

• Occupational disease notification and compensation.