[Acute megakaryoblastic leukemia. Relation to trisomy 21].

Two cases of acute megakaryoblastic leukemia in a 4 month-old and a 13 year-old girl are described. In the first case who presented with a large hepatomegaly and portal fibrosis, the diagnosis was made from the surface phenotyping of megakaryoblasts; a trisomy 13, 14 and 19 and an extra chromosome X were present in the bone marrow. An electron microscopy study of megakaryoblasts was necessary to identify the second case. Both children died shortly after treatment (cytosine-arabinoside at low dosage in the first case and polychemotherapy in the second). The 51 other cases reported in the literature are reviewed.