Idiopathic pulmonary hemosiderosis: ultrastructural studies and responses to azathioprine.

Two boys are presented who fulfilled criteria for a diagnosis of idiopathic pulmonary hemosiderosis. A lung biopsy specimen from the first patient showed alveolar-capillary basement membrane abnormalities, together with abnormalities of capillary endothelial cells and hemosiderin-laden macrophages. A lung biopsy specimen from the second patient showed mainly capillary endothelial abnnormalities and interestitial fibrosis. Both patients had a noticeable improvement in symptoms and relative stabilization of their roentgenographic and pulmonary function abnormalities following azathioprine therapy.