Alveolo-capillary membrane in primary pulmonary hypertension.

This study was undertaken to detect diagnostic ultrastructural changes in the alveolar walls in biopsies of patients with primary pulmonary hypertension (PPH). Open lung biopsies from 8 patients referred to the Hospital of the University of Pennsylvania were available for study. By light microscopy 4 patients were diagnosed as having plexogenic pulmonary arteriopathy, 2 thromboembolic arteriopathy and 2 veno-occlusive (PVOD) disease. In 4 patients the diagnosis of PPH was further confirmed at autopsy. Changes were observed in the basement membrane of the alveolar capillaries in 6 of the patients. These consisted in marked thickening and duplication of the basement membrane of alveolar capillaries in the 4 patients with the plexogenic form of pulmonary hypertension. Patients with PVOD instead showed uniform thickening of the basement membrane. No changes were detected in the 2 biopsies of patients with the thromboembolic form of PPH. We conclude that ultrastructural studies contribute significantly to the precise characterization of pathologic changes in the lungs of patients with PPH.