[Ultrastructural examination and stereological study of bone marrow megakaryocytes in children with idiopathic thrombocytopenic purpura].

The ultrastructure and surface architecture of megakaryocytes (MK) were examined in 19 children with idiopathic thrombocytopenic purpura (ITP), the stereological parameters of alpha granules were computed. Transmission electron microscopy revealed vacuolization of cytoplasma of MKs, decrease in the number of alpha granules and degeneration of mitochondria. The granular MKs of chronic ITP appeared to be focal distribution of demarcation membrane system (DMS) in two cases with formation of large membrane complex. Staining with tannic acid indicated vesicular, tubular and cisternal dilation of DMA. Rough endoplasmic reticulum and Golgi complex were much more abundant than in normal MKs. In 5 cases of ITP, we found emperipolesis of hematopoietic cells within MKs. Under scanning electron microscopy many MKs showed complex surface processes including crowded blebs, villi and giant irregular projections. Occasionally perforations on the surface membrane could be seen. Stereological analysis showed that the Nv, Vv, and Sv of alpha granules of both acute and chronic ITP were markedly decreased as compared with normal control (P < 0.001), and the Nv of acute ITP was notably less than that of chronic ITP (P < 0.05). However the S/V, M.DIAM. and M. VOL. were no significant difference among normal control, acute and chronic ITP (P > 0.05).