45,X 46,X,IDIC(YQ) MOSAICISM - CLINICAL, CYTOGENETIC, AND MOLECULAR STUDIES IN 4 INDIVIDUALS/

45,X/46,X,idic(Yq) mosaicism is associated with a variety of sex pheno types, including Ullrich-Turner syndrome (UTS), intersexuality, and co mplete male. It remains unclear whether the phenotypic variability res ults from a dilutional effect by the 45,X cell line in the primordial gonad or an abnormality of the SRY gene (SRY), We conducted cytogeneti c and molecular studies on four patients with such mosaicism, two of w hom had a complete male phenotype and two who had UTS. Chromosome anal yses showed that the frequency of cells carrying an idic(Yq) chromosom e in peripheral blood lymphocytes and skin fibroblasts was not related to the given sex phenotype. The SRY, PABY, and ZFY genes were present in all four patients. A fluorescence in situ hybridization (FISH) stu dy showed that both a patient with a complete male phenotype and anoth er with UTS had duplicate copies of SRY in their idic(Yq) chromosomes, whereas a patient with UTS had a single copy of the gene. These findi ngs suggested that the coexisting 45,X cell line is more influential o n the determination of the sex phenotype in individuals with 45,X/46,X ,idic(Yq) mosaicism, (C) 1998 Wiley-Liss, Inc.