Sir.—There have been several reports of individuals with the 47,XYY chromosome constitution developing acute lymphoblastic leukemia (ALL), acute myeloid leukemia, chronic myelogenous leukemia, or other malignancies.1-13 Furthermore, it has been speculated that individuals with constitutional chromosomal abnormalities, including the 47,XYY constitution, have a predispositon to develop leukemia, similar to that observed with trisomy 21.5,8,14 We report herein a case of a 3½-year-old boy who was diagnosed as having ALL and was found to have a 46,XY/47,XYY constitutionally mosaic karyotype, with the aberrant hyperdiploid chromosome clone arising from the XY-bearing cell line.
—A previously healthy 3½-year-old boy presented with a history of fever, cough, and pallor of 1 week's duration. The physical examination findings were normal except for pallor. Growth and development were normal. A complete blood cell count showed pancytopenia. A bone marrow examination showed patchy infiltration with leukemic lymphoblasts, with areas of the marrow