Morphogenesis in chronic Pneumocystis carinii infection--discussion of three cases

The clinical and histological features of three HIV1-positive patients are reported of whom two showed persistent focal lesions on serial chest X-rays without any demonstrable lesion on repeated bronchoscopies. The third patient presented with recurrent pneumothorax. By thoracoscopy peripheral lung tissue was obtained in all cases, showing localized histomorphological findings compatible with a prolonged interstitial reaction around Pneumocystis carinii (PC) organisms and their breakdown products. Based on the finding of foreign body granulomas and an increased number of alveolar macrophages, we propose a hypothetical pathway for the development of this unusual reaction to PC infection focusing on the possible secretion of tumor necrosis factor alpha by activated macrophages. By this model the unusual features of PC infection in our patients and in the literature could be explained. Furthermore, in these cases possibly an additional oral or intravenous treatment might be indicated.