Ultrastructural diagnosis of histologically atypical idiopathic thrombocytopenic purpura.

The histological and electron microscopic findings in the spleen of a 61-year-old white man with corticosteroid-unresponsive idiopathic thrombocytopenic purpura (ITP) are described. Light microscopically, the spleen lacked features characteristic of ITP, such as germinal centers and foamy histiocytes. Ultrastructurally, however, platelet phagocytosis, which is diagnostic of this entity, was readily demonstrable in splenic cord macrophages.