Morphogenesis of pulmonary veno-occlusive disease in a newborn. Image analysis study.

A 9-day-old girl was admitted to hospital because of respiratory distress. The girl died on the 11th day of life shortly after an haemodynamic study and the autopsy disclosed a pulmonary veno-occlusive disease with lesions in relatively early stages of development. Morphological pattern and computerized image analysis data induce to rule out a thrombosis as a previous event to the development of fibrotic changes and point to a "primary" intimal involvement, presumably triggered by an endothelial injury, determining a myxoid change of the intima and leading to a cellular proliferation and ultimate fibrotic occlusion of the small pulmonary veins. Apparently the lesions progress from the smaller pulmonary veins to the larger ones, in which the involvement is focal in character and related to the openings of collateral branches. The homogeneous character of the more recent lesions in the larger veins is in contrast to the heterogeneity of the fibrotic process in the smaller ones.