Karyotype investigations using classical cytogenetics, fluorescence in situ hybridization (FISH) and polymerase chain reaction (PCR) techniques were used for the characterization of Y chromosome structural anomalies found in two patients with ambiguous genitalia and features of Turner syndrome. Both exhibited mosaic karyotypes of peripheral blood lymphocytes. The karyotype was 45,X[90]/ 46,X,idic(Y)(p11.3).ish idic(Y)(wcpY+, DXYS130++,SRY++,DYZ3++,DYZ1++, DYS224++)[10] in one case, and the karyotype was 45,X[65]/46,X, idic(Y) (q11).ish idic(Y)(SRY++, RP11-140H23-)[35] in the other case. Derivative Y chromosomes were different in shape and size and positive for the SRY gene, a common underlying element of ambiguous genitalia phenotypes. These results add new information concerning the role of Y chromosome structural abnormalities in sex determination pathway perturbation which are poorly understood, and highlight the importance of the sex chromosomes integrity for a normal sex phenotype development.          

   Key words: Ambiguous genitalia; Fluorescence in situ hybridization (FISH) techniques; Isodicentric(idic(Y) chromosome; Polymerase chain reaction (PCR) markers ; Turner syndrome features