Chromosome clues to acute leukemia in Down's syndrome

Surprisingly few cases of Down's syndrome with acute leukemia have been documented by chromosome banding studies of the leukemia cells. We studied a Down's syndrome child with acute myelomonocytic leukemia and found that, including this case, only 24 cases of Down's syndrome and acute leukemia have been reported with chromosome banding analysis. Twenty-three of the patients had a trisomy 21 chromosome complement, whereas, one had a translocation. The types of acute leukemia included acute myeloblastic leukemia, acute myelomonocytic leukemia, acute monoblastic leukemia, acute lymphoblastic leukemia, and erythroleukemia. Only three cases had chromosomes missing from the leukemic cells. Sixteen of the 24 patients had extra chromosomes in their malignant cells. Chromosomes #8 and #21 were extra in six cases each and chromosomes #19 and #22 were extra in four cases each. Chromosome rearrangements were observed in nine cases. Three of the nine cases had partial deletion of the long arm of chromosome #6. Cases of Down's syndrome with acute leukemia need to be reported with high-resolution chromosome banding of the leukemia cells. There is as yet no clear chromosome clue as to the precise basis of the etiologic association between Down's syndrome and acute leukemia.