HUMAN ALVEOLAR CAPILLARIES UNDERGO ANGIOGENESIS IN PULMONARY VENOOCCLUSIVE DISEASE

The bronchial circulation undergoes angiogenesis in several pathologic al conditions, such as lung neoplasm and bronchiectasis, but whether t he pulmonary circulation can do this has been questioned. A woman trea ted with mitomycin C and 5-fluorouracil developed progressive, fatal p ulmonary hypertension over 5 months. In addition to light and transmis sion electron microscopic examination of her lung, her pulmonary vascu lature was cast and the casts were studied with scanning electron micr oscopy. Light microscopy showed that she had pulmonary veno-occlusive disease and angiomatoid capillary growth in the alveolar walls. Transm ission electron microscopy confirmed the presence of pulmonary hyperte nsion and showed thickened endothelial basement membrane. Scanning ele ctron microscopy of the cast blood vessels showed distortion and destr uction of alveolar capillaries prohibiting the passage of erythrocytes . Large new capillaries developed on top of, and were connected to, th e shrivelled capillaries that made up the alveolar wall. The new capil laries were larger and fewer, which reduced the alveolar-capillary int erface. Arteries and veins were irregularly narrowed and the veins had broad muscularity. Oedema was present, and the pulmonary lymphatics w ere extensively cast, especially in the lobular septa, but the lymphat ics had a normal appearance. It appears that this patient suffered ext ensive capillary damage and venous occlusion and that the response was extensive new capillary formation, sometimes in angiomatoid configura tions, and hypertrophy of pulmonary veins and arteries. Casting the mi crovasculature and viewing it with scanning electron microscopy identi fied new alveolar capillaries in this patient with acquired pulmonary hypertension.