Novel karyotype in the Ullrich-Turner syndrome--45,X/46,X,r(X)/46,X, dic(X)--investigated with fluorescence in situ hybridization.

A 10-year-old girl with Ullrich-Turner syndrome was found to have the novel karyotype 45,X/46,X,r(X)(p11q11)/46,X,dic(X)(p11). Fluorescence in situ hybridization (FISH) with the alpha satellite X centromere probe established the origin of the small ring chromosome. Scanning a large number of cells by interphase FISH showed that the dicentric (X) was the least prevalent cell line. The common breakpoint of Xp11 suggests a sequence of errors as the mechanism whereby these 3 distinct cell lines have arisen.