Nonspecific interstitial pneumonitis: a common cause of pulmonary disease in the acquired immunodeficiency syndrome.

During a 4.4-year period, nonspecific interstitial pneumonitis was seen in 41 of 110 (38%) patients with the acquired immunodeficiency syndrome and accounted for 32% (48/152) of all episodes of clinical pneumonitis. Diffuse alveolar damage was typically a feature of nonspecific interstitial pneumonitis, but neither lung biopsy nor bronchoalveolar lavage detected a pathogen. Of these 41 patients, 13 had no associated pulmonary tumor and had not been exposed to pulmonary toxins, whereas 28 patients had either concurrent pulmonary Kaposi sarcoma, previous experimental therapies, or a history of pneumocystis pneumonia or drug abuse. Of these 41, 23 had normal chest radiographs. The clinical features of patients with nonspecific interstitial pneumonitis were similar to those of patients with pneumocystis pneumonia, although histologic findings showed less severe alveolar damage in patients with nonspecific interstitial pneumonitis (p less than 0.001). Pathologic evaluation and clinical follow-up suggest that many clinical episodes of pneumonitis in patients with the acquired immunodeficiency syndrome are due to nonspecific interstitial pneumonitis of unknown cause.