Chemotherapy in Treating Children With Down Syndrome and Myeloproliferative Disorder, Acute Myelogenous Leukemia, or Myelodysplastic Syndrome

DISEASE CHARACTERISTICS: * Cytogenetically proven Down Syndrome (constitutional trisomy 21) with transient myeloproliferative disorder (TMD), myelodysplastic syndromes (MDS), or acute myelogenous leukemia (AML) * Must be confirmed by bone marrow aspirate, cerebrospinal fluid exam, or blood test * Trisomy 21 mosaicism allowed * Group I: * Diagnosis of TMD in patients no older than 90 days at initial presentation * Must have nonerythroid blasts (any amount) in the peripheral blood and one of the following: * Verification with a second sample * More than 5% bone marrow blasts * Hepatomegaly and/or splenomegaly * Lymphadenopathy * Cardiac or pleural effusions OR * Histologically or cytologically proven TMD with blasts in an affected organ or in fluid (pericardial, pleural, or peritoneal) * Bone marrow aspirate is required * Group II (closed to accrual as of 6/24/04): * Diagnosis of MDS or AML (except M3 subtype) in patients older than 90 days with more than 29% blasts in bone marrow (with or without history of TMD), or any of the following histologies: * Refractory anemia (RA) * RA with excess blasts (RAEB) * RAEB in transformation * RA with ringed sideroblasts (RARS) * Primary cytopenia (later confirmed by bone marrow aspirate as due to marrow hypoplasia) defined by one or more of the following: * Absolute neutrophil count less than 500/mm\^3 * Untransfused platelet count less than 30,000/mm\^3 * Untr…