Granulomatous Pneumocystis carinii Pneumonia in Three Patients with the Acquired Immune Deficiency Syndrome: Conclusion

Granulomatous Pneumocystis carinii Pneumonia in Three Patients with the Acquired Immune Deficiency Syndrome: ConclusionThe entire subject of typical and atypical appearances of P carinii pneumonia was reviewed by Weber et al in 1975, with the addition of other occasionally occurring atypical features such as interstitial fibrosis, a dense interstitial infiltrate, severe infiltration of alveolar macrophages, and calcification. These authors found atypical histologic features present in 69 percent of the 36 cases they studied. Nearly all of these patients had either a primary immunodeficiency or had been immunosuppressed secondary to chemotherapy for malignancy or transplantation. so
We believe that our cases are the first descriptions of this histologic variant in the setting of the AIDS. In two of the three cases, the only organism implicated by all available studies was P carinii. Although cultures of one of the cases eventually grew Mycobacterium avium-intracellulare, we believe that the granulomas we observed in this case were in large part due to the presence of Pneumocystis, since the organism was seen directly within the granulomas, and no acid-fast bacilli were found. The possibility of coexistent infection in this case remains.

These cases are especially interesting in light of the fact that well-formed granulomas are generally not seen in AIDS patients, even in the presence of mycobacterial infection. Although this is generally ascribed to these patients’ defective T-cell function, one of us has observed granuloma formation in a study of nude rats injected with BCG; thus, proper T-cell function may not be absolutely essential for the granulomatous response. Unfortunately, studies of T-cell function such as T-helper/suppressor ratios were not available in our cases.
Finally, P carinii may rarely be found in other organs, usually lymph nodes or spleen, with widespread dissemination also possible. Again, this nearly always occurs in the setting of an immunosup-pressed patient, with recent reports documenting both extrapulmonary mass lesions containing Pneumocystis and disseminated P carinii in AIDS patients. In some of these cases the tissue response to the organism has been granulomatous, although most have revealed an acellular exudate similar to that typically seen in the lung. We believe that with the current incidence of AIDS and the frequent occurrence of P carinii pneumonia as one of its components, it is essential to keep in mind all of the possible radiographic and pathologic manifestations of this organism, no matter how rare its atypical presentations may be.
Since this article was submitted, we have seen an additional case of granulomatous Pneumocystis carinii pneumonia in a patient with Hodgkins disease and therapy-associated acute myelogenous leukemia. There was no evidence of AIDS in this patient.