There have been several reports of the association between Down's Syndrome and acute megakaryoblastic (M7) leukemia (AMKL). The diagnosis of this rare form of leukemia has been better delineated by the use of the platelet peroxidase reaction and the antifactor VIII antibody immunoperoxidase test. In the past, the prognosis of patients with a combination of Down's Syndrome and AMKL has been extremely poor, with a median survival of 6.9 months for 11 reported cases in the literature. The present report reviews the previously reported cases and describes a unique patient with mosaic Down's syndrome and AMKL with favorable response to therapy.

The experience with the treatment of malignant histiocytosis has been disappointing. Despite modest treatment success with a combination of cyclophosphamide, Adriamycin (doxorubicin), vincristine and prednisone, the overall prognosis remains poor. There are only a few reports of prolonged complete remissions in pediatric patients. The following report describes two children who have had long-term remission with an aggressive combination chemotherapy program that included intrathecal prophylaxis. The chemotherapeutic regimen described merits further evaluation in a larger number of patients.