Chromosome patterns in 26 South African children with acute nonlymphocytic leukemia (ANLL).

Of 46 black leukemic children 52% had acute nonlymphocytic leukemia (ANLL), whereas only 11% of 62 white leukemic children had the disease. An abnormal karyotype was found in 73% of the 26 children with ANLL, and the majority of abnormal karyotypes were pseudodiploid. "Balanced" translocations were noted in 10 children, of whom four had t(8;21) associated with M2 ANLL, two had t(15;17) and M3 ANLL, two had a t(9;22), one child with M5 ANLL had t(10p;11q), and an infant with congenital M5 ANLL had t(8;16). Monosomy #7 was detected in two preleukemic children who subsequently developed M4 ANLL. Hyperdiploidy was present in only three cases. These patterns were compared with those of other published series, confirming the increased frequency of chromosome abnormalities in children with ANLL. The differing ratio of ANLL:ALL, some of the distinctive clinical features, and the high frequency of detectable chromosome abnormalities in black children may be reflections of a particular oncogenic agent(s) within their environmental background that could be responsible for the initiation of the leukemic process.