Respiratory manifestations of connective tissue disease

Pleuropulmonary disease is a common feature of the following connective tissue diseases: systemic lupus erythematosis (SLE), rheumatoid arthritis (RA), progressive systemic sclerosis (PSS), mixed connective tissue disease (MCTD), polymyositis/dermatomyositis (PM/DM), and Sjögren's syndrome (SS). Features common to most of these disorders include pleurisy with effusion and interstitial lung disease. Pleural effusions caused by SLE and RA have certain characteristics on pleural fluid analysis that aid in diagnosis, but infection and other causes of effusion must be excluded. Interstitial lung involvement is usually indolent in onset, but a more rapidly progressive course over weeks to a few months may mimic infection. Several drugs used to treat connective tissue diseases may cause interstitial disease, increase susceptibility to infection, or both. This complicates differential diagnosis. Acute lupus pneumonitis and SLE-related alveolar hemorrhage are usually fulminant processes, often associated with fever. Diagnosis of these conditions always requires exclusion of infection. Rheumatoid nodules may mimic infectious and neoplastic lung diseases. Needle biopsy helps reduce the likelihood of infection or malignancy, but open lung biopsy is needed if a firm diagnosis of rheumatoid nodules is required.