Pleural Involvement in Connective Tissue Disease

Pleural involvement is a common manifestation across multiple connective tissue diseases (CTDs), with characteristic features helping differentiate from non-CTD causes. In systemic lupus erythematosus (SLE), pleuritis occurs in 30-50% during disease course, often as one of the earliest manifestations; presents with pleuritic chest pain, with or without effusion, typically small to moderate, bilateral or unilateral exudates with elevated lymphocytes, ANA-positive cells, low complement, and antinuclear antibodies in fluid. SLE pleural disease typically responds to corticosteroids and is rarely chronic.

In rheumatoid arthritis (RA), pleural involvement is less common (3-5%) but more striking: predominantly affects men with established seropositive RA, characterized by chronic exudative effusion with very low glucose (<30 mg/dL — pathognomonic), low pH (<7.30), high LDH, and low complement; rheumatoid factor in fluid; cytology may show 'rheumatoid cells' (multinucleated giant cells, necrotic cells); pleural biopsy may demonstrate characteristic palisading granulomatous inflammation. RA pleural disease may be chronic and difficult to manage, sometimes leading to fibrothorax.

Other CTDs with pleural involvement include systemic sclerosis (less common pleural disease, more typically interstitial lung disease), inflammatory myopathies (dermatomyositis/polymyositis with possible pleural disease and ILD), Sjögren's syndrome (small effusions with lymphocytic exudate), mixed connective tissue disease, and ANCA-associated vasculitides (granulomatosis with polyangiitis can cause pleurisy). Diagnostic approach includes thoracentesis with comprehensive fluid analysis (cell count, glucose, pH, LDH, autoantibodies, complement), serologic markers (ANA, anti-dsDNA, complement, RF, anti-CCP), imaging, and exclusion of infection (TB, parapneumonic) and malignancy. Treatment addresses both pleural manifestation (drainage if large/symptomatic, NSAIDs for pleuritis pain) and underlying systemic disease (corticosteroids first-line, methotrexate, azathioprine, mycophenolate, hydroxychloroquine, biologics like rituximab for resistant cases).