PARTIAL CHROMOSOME-21 AMPLIFICATION IN A CHILD WITH ACUTE LYMPHOBLASTIC-LEUKEMIA

Monosomy 21 and metacentric markers corresponding in size to chromosom es 8 to 12 were found as the only clonal chromosomal changes in a chil d with acute lymphoblastic leukemia (ALL). Chromosome painting with a whole chromosome 21-specific probe showed that the marker originated f rom chromosome 21. Fluorescence in situ hybridization with yeast artif icial chromosome (YAC) probes to chromosome 21 showed genomic amplific ation with two, four, or more copies of the probed DNA sequences prese nt an the marker. The most amplified regions of chromosome 21 were cen tromeric and telomeric to the Down's syndrome region. This observation supports the notion that amplification of only parts of chromosome 21 may be important in the leukemogenic process in spite of the high inc idence of complete trisomy 21 in ALL. (C) 1995 Wiley-Liss, Inc.