Splenic ultrastructural features in idiopathic thrombocytopenic purpura.

Spleen samples from idiopathic thrombocytopenic purpura (ITP) patients were investigated for ultrastructure and peroxidase activity. The white pulp was characterized by the presence of many large secondary lymphatic follicles and periarteriolar sheaths formed from lymphocytes and plasma cells. Their ultrastructural details substantiate the process of lymphocyte differentiation and the immunopathologic mechanism of the disease. The vascular lesions proved to be subendothelial hyaline deposits. The platelet destruction process and phagocytosis resulted in the occurrence of fibrin clusters. Macrophages were also described as stainable body macrophages, foamy macrophages and a third type dealing with fibrin phagocytosis.