Transient myeloproliferative disorder (transient leukemia) and hematologicmanifestations of Down syndrome

Transient Myeloproliferative Disorder (Transient Leukemia) is found in appr oximately 10% of newborn infants with Down Syndrome. It is characterized by the large numbers of megakaryoblasts in the peripheral blood, variable thr ombocytopenia and, in a minority of cases, by a lethal course with hydrops fetalis or progressive hepatic fibrosis. Evidence is presented that this di sease is truly leukemia, which, in most cases, recovers spontaneously. Ther e is evidence that hematopoiesis is abnormal in Down Syndrome children who do not have leukemia. These abnormalities of red cells, platelets, and gran ulocytes are reviewed.