Ultrastructure of megakaryocytes from a thrombocytopenic family member.

Electron micrographs of 4 characteristic megakaryocytes from 1 affected individual (IV-10) are shown, arranged from least to most differentiated. (A) Very early megakaryocyte with a minimal demarcation membrane (DM) system; the diameter is 11 μm. (B and C) Most common megakaryocytic cells include a more obvious demarcation membrane system and occasional developing platelets (P); the diameters are 12 and 15 μm, respectively. (D) Most fully differentiated megakaryocyte observed with increased demarcation membranes; the maximum diameter is 14 μm. Nuclei (N) are indicated. Magnification, 2900 × for panels A, B, and D; 2300 × for panel C.