Comparison of marrow megakaryocyte ploidy distribution for HIV-infected thrombocytopenic patients and normal subjects. The megakaryocyte ploidy distribution for 20 normal subjects is depicted by the open bars. The ploidy distribution of marrow megakaryocytes for six thrombocytopenic HIV patients is shown by the hatched bars. While there is a significant increase in 64N megakaryocytes in patients with HIV thrombocytopenia (P < .0001), the overall megakaryocyte ploidy is nearly normal, because of the increase in 4N and 8N cells at the expense of 16N cells. The ploidy distribution in HIV thrombocytopenic patients is interpreted to represent TPO-driven stimulation of megakaryocyte growth and development.