Radiographic and bronchoalveolar lavage features of Pneumocystis pneumonia (PCP)

Patients with acquired immunodeficiency syndrome (AIDS) who develop PCP typically present with a cough, fever, and exertional dyspnea. A chest radiograph (panel A) characteristically has interstitial and alveolar infiltrates in a perihilar distribution. In AIDS patients, BAL demonstrates the associated inflammatory cell burden, rich in lymphocytes (CD8+ T cells) and macrophages, with a relative paucity of neutrophils (see the Wright-Giemsa stained smear in panel B). A methenamine silver stained smear of BAL fluid from patients with AIDS (panel C) reveals abundant numbers of Pneumocystis cyst forms. In immunocompromised patients without AIDS, PCP has a more fulminant onset and can rapidly progress to respiratory failure. The chest radiograph from such patients (panel D) usually has diffuse lung infiltrates in a pattern that is consistent with severe lung injury, whereas the BAL fluid (see the Wright-Giemsa stained smear in panel E) has an abundance of inflammatory cells, particularly neutrophils. A methenamine silver stain of the BAL fluid (panel F) again demonstrates cyst forms, although usually significantly fewer than in patients with AIDS (compare with panel C).