Abstract
A 1 10/12 year-old boy with Down's syndrome (DS) was admitted to the Saitama Children's Medical Center with anemia and petechiae in March, 1982. On admission physical examination showed the presence of hepatosplenomegaly and systolic heart murmur. His hemoglobin was 9.9 g/dl, platelet count 4.6×109/l and white blood cell 3.7×109/l with 6% blasts. He was diagnosed as having refractory anemia with excess of blasts according to FAB classification. Chromosome analysis of cells from bone marrow revealed 48, XY, +11, -15, +21, +der(15)t(1;15)(q25;p11). Subsequent follow-up without chemotherapy showed no consistent change. In September, however, leukemic cells increased to 70% in the bone marrow. The blasts were negative for peroxidase, periodic acid-Shiff, α-naphtyl acetate esterase and α-naphtyl butylate esterase, positive for acid phosphatase stainings. About 70% of blasts were shown to posses platelet peroxidase on electron microscopic study. Cell marker studies using KOR-P77, which is monoclonal antibody to the platelets, showed to be positive, He was diagnosed as having acute megakaryoblastic leukemia (AMkL, M7 of FAB). He was treated with aclarubicin and enocitabin, and obtained complete remission. After 3 courses of this regimen he relapsed and died of pneumonia.
AMkLs with DS in the literature were discussed. A trisomic for a long arm of chromosome 1 in this case, which has been frequently reported in solid tumors, has been described in 5 cases with acute leukemia and Down's syndrome. We considered that addition of no. 21. chromosome was associated with leukemogenesis of AMkL.
