Collagen vascular diseases.

Systemic lupus erythematosus, polymyositis/dermatomyositis, connective tissue disease, and polyarteritis nodosa are the collagen vascular diseases (CVDs) most likely to mimic pneumonia. All can be associated with an acute illness characterized by fever, cough, dyspnea, pleural symptoms, and an abnormal chest roentgenogram. Recognition of the CVD-associated pulmonary process requires sophisticated serological testing and chemical pleural fluid analysis coupled with the exclusion of pulmonary infection and pulmonary embolization. This review emphasizes the clinical characteristics of these CVDs, the diagnostic tests most helpful in recognizing them, and the differential diagnosis of pleuroparenchymal disorders that occur in these patients.