IDIOPATHIC PULMONARY HEMOSIDEROSIS - EVIDENCE OF CAPILLARY BASEMENT-MEMBRANE ABNORMALITY

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Abstract
EM examination of a lung biopsy obtained from a child in the active stage of idiopathic pulmonary hemosiderosis disclosed prominent changes in the basement membrane of alveolar capillaries. The literature shows that a structural defect of lung capillary walls in this disease was previously proposed on theoretic grounds not adequately documented at the ultrastructural level. Concentric multilayering of pulmonary capillary basal lamina was observed in this material. This is a rare phenomenon in this location, although it is well described in extrapulmonary, microcirculatory beds and is probably a nonspecific reaction to vascular injury. The conceptual difficulties attending a definition of idiopathic pulmonary hemosiderosis are briefly discussed.