CONGENITAL ALVEOLAR-CAPILLARY DYSPLASIA - RARE CAUSE OF PERSISTENT PULMONARY-HYPERTENSION

We report on a rare case of fatal congenital alveolar capillary dyspla sia. The newborn boy of a 37 weeks' normal gestation suffered from per sistent pulmonary hypertension without any cardiovascular malformation and died at the age of 4 weeks despite intensive treatment. The autop sy tissue was examined histologically, immunohistochemically, and ultr astructurally. Moreover, a three-dimensional tissue reconstruction bas ed on serial sections was performed comparing the affected lung with n ormal lung tissue. We observed a unique pattern of pulmonary dysplasia : An extreme decrease of capillaries was localized centrally within th ickened intra-acinar septa instead of capillaries intensely neighborin g pneumocytes; ectatic veins normally running in the interlobular sept a were found to accompany intralobular bronchovascular bundles, denyin g a clear distinction between pulmonary and bronchial veins; small mus cular pulmonary arteries extended to the precapillary level and type 2 pneumocytes exceeded by far the type 1 pneumocytes, inverting the nor mal ratio. In summary, alveolar capillary dysplasia is assumed to be a primary capillary disorder of unknown origin, which possibly involves the regular differentiation of pneumocytes, according to the close al veolocapillary relationship during pulmonary ontogenesis. We consider the venous alterations as being part of the dysplasia, whereas the art erial phenomena might occur secondarily. Recent reports on affected si blings suggest a genetic component of pathogenesis.