When the lungs are involved by connective tissue disease.

Pulmonary involvement by a connective tissue disease can result in clinically important complications. Pathogenic mechanisms vary from granulomatous reaction and interstitial inflammation to primary vasculitis and immune complex-mediated disease. Understanding the pulmonary complications of connective tissue diseases is challenging in that several distinct patterns of involvement are associated with the same disease but the same lung abnormalities are found with several different diseases. Early recognition and treatment of pulmonary involvement may offer the patient a better chance of recovery from serious conditions that often carry a grim prognosis if undetected.