Specific minor chromosome deletions consistently occurring in myelodysplastic syndromes.

Forty-two patients with refractory anemia with or without sideroblasts have been investigated cytogenetically one to nine times (mean, 3) over a period of 1-36 months (mean, 16). The initial investigation showed numerical and/or major structural abnormalities [t(3;3), 5q-, -7, or 7q-, 11q-] in nine patients (21%). In addition, minimal terminal deletions were observed in 2p, 8p, 9p, 11p, 12p, 17p, 17q, 20q, and Xp. The detection of these deletions, which have not been reported earlier, was due to consistent application of the high resolution technique, G-banding without trypsin, and metaphase photography on large size negatives. Each deletion occurred as a clone on one or more occasions in 1-17 patients (mean, 7). One or other clonal minimal deletion was observed in 32 patients (76%). Preliminary indirect evidence indicates that alone or together with other factors the deletions promote leukemic transformation of refractory anemia.