Granulomatous Pneumocystis carinii Pneumonia in Three Patients with the Acquired Immune Deficiency Syndrome: Discussion
Pneumocystis carinii has now become a particularly prevalent pathogen in the increasing population of patients with AIDS. It thus becomes increasingly relevant to discuss all of the organisms manifestations with special attention to its unusual presentations. While the classic radiographic appearance of hazy, bilateral alveolar infiltrates beginning in perihilar areas and progressing to diffuse involvement is certainly most common, it has become evident in recent years that other appearances are possible. These include segmental or lobular consolidation, nodular densities, and even cavitating lesions. These appearances may mimic those of tuberculosis and have led to initial clinical suspicion of mycobacterial infections, as was true in our cases 1 and 2.
Although the diagnosis of P carinii pneumonia may be suspected radiographically, the identification of the organism in a clinical specimen is the only definitive diagnostic method. The typical histologic appearance of the infection on routine hematoxylin-eosin-stained sections is well-known, consisting mainly of a foamy, intra-alveolar eosinophilic exudate which is devoid of cells and a mild to moderate interstitial infiltrate of plasma cells, lymphocytes, and occasional histiocytes. The organism can readily be demonstrated, usually within the exudate or, occasionally, within the alveolar septa, using Grocott methenamine silver stains. so
Granulomatous reactions in which the only demonstrable organism is P carinii have been recognized for some time. The first report we could find was by Cruickschank in 1975, describing a patient who, following renal transplantation and subsequent immunosuppressive therapy, developed repeated bouts of pneumonia, the diagnosis of granulomatous pneumocystosis eventually being made on open lung biopsy. The granulomas in that case consisted of noncaseating clusters of epithelioid cells, most of which were present in the alveolar spaces, with a few present in the interstitium. A few lymphocytes were also seen, and only an occasional multinucleated giant cell was found. Pneumocystis carinii was seen diffusely throughout the granulomas.
Since this initial description, other reports have noted necrotizing granulomas,- one of which showed fibrosis to the degree usually seen in later-stage sarcoid granulomas. Both patients in these reports carried a diagnosis of malignant lymphoma, and at least one of them had been undergoing chemotherapy.
Tags: AIDS, biopsy, carinii pneumonia