Variant Philadelphia translocations in CML: correlation with fragile sites.

Of 175 CML patients studied, 14 variants were found, seven of which are presently described. The breakpoints involved in the translocation, other than 9q34 and 22q11, are 3p21, 5q13, 6p21, 7q22, 10q22, and 11p13. Fragile sites were investigated in some of these patients. In two cases a coincidence between fragile site location and breakpoint of the third chromosome involved in Philadelphia formation was found. This observation suggests that the fragile sites can lead to Ph variants in patients developing CML.