Bone marrow in megakaryocytic disorders.

Megakaryocytic disorders induce serious consequences: myelofibrosis and osteomyelosclerosis, hemorrhage, and thrombosis. They are characterized by four main structural types: myeloproliferation, dysmegakaryocytosis, amegakaryocytosis, and secondary megakaryocytosis. Whereas the first and third are primarily defined by histology, the second and fourth are to be interpreted only in the context of clinical findings. Nevertheless, bone marrow biopsy has revealed marked quantitative and qualitative anomalies of megakaryocytes also in these groups: isolation, pleomorphism, and degeneration of nuclei, and immaturity, vacuolization, and disruption of cytoplasm. The pathophysiologic impact of these impressive changes is almost unknown. It deserves further consideration.