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The respiratory section of lung biopsies from patients with primary pulmonary hypertension (PPH) was studied by electron transmission microscopy. The alterations found allow to suggest the presence of apoptotic degeneration of cells of the capillary endothelium and lung epithelium, this being confirmed also by an alveolar macrophages increase. The role of apoptosis in the PPH pathogenesis is discussed.

Morphological investigation of 12 cases of primary pulmonary hypertension (PPH) (4 males and 8 females, from 20 to 48 years old, duration of the disease from 1 to 10 years) is performed. Heart weight increase (from 390 to 640 g) and thickening of the right ventricle wall were observed. 3 groups were distinguished on the basis of histology: 1) plexigenic pulmonary arteriopathy (PPA)-2 cases, 2) recurrent pulmonary thromboembolism (RPT)-5 cases, 3) vein-occlusive disease (VOD-5 cases. The third group was divided into two subgroups: vascular-occlusive disease (VOD) with thrombotic lesions of arteries and veins and vein-occlusive disease proper (VOD-p) with thrombosis of pulmonary veins only. Morphometrically, thickening of arterial intima and media was found in PPA and RPT and in some cases of VOD-p. The thickening of the above layers in veins found in some cases of PPA and RPT was obviously secondary and indicated the development of mixed pre- and postcapillary pulmonary hypertension.