Acute megakaryoblastic leukemia with translocation t(1;22)(p13;q13) in a 10-week-old infant.

A 10-week-old girl without Down syndrome developed an acute megakaryoblastic leukemia (AMKL). Bone marrow aspirates and biopsy showed megakaryoblastic infiltration with myelofibrosis. The diagnosis was made based on the findings that the positive reactions of leukemic cells to platelet peroxidase and to monoclonal antibodies which recognize platelet-specific surface glycoprotein (GP) IIb/IIIa and GP78. The blasts also showed myeloid and monocytoid differentiation antigens. The leukemic cells had a karyotype of 46,XX,t(1;22)(p13;q13). Our case and two other infantile cases reported by other investigators establish the novel association of the t(1;22) with AMKL.