TETRASOMY-21 IN MEGAKARYOBLASTIC LEUKEMIA

A 23-month-old female evaluated for profound anemia proved to have meg akaryoblastic leukemia. The diagnosis is based on examination of bone marrow morphology, cytochemical characteristics, and immunophenotype. The chromosome complement of unstimulated blast cells in peripheral bl ood and bone marrow was 48,XX, +21, +21. Tetrasomy 21 is the sole clon al cytogenetic abnormality in this patient with megakaryoblastic leuke mia. The constitutional complement of the patient is normal female, 46 ,XX.