DETECTION OF Y-CHROMOSOME SEQUENCES IN A 45,X 46,XXQ- PATIENT BY SOUTHERN BLOT ANALYSIS OF PCR-AMPLIFIED DNA AND FLUORESCENT IN-SITU HYBRIDIZATION (FISH)/

In some cases of gonadal dysgenesis, cytogenetic analysis seems to be discordant with the phenotype of the patients. We have applied techniq ues such as Southern blot analysis and fluorescent in situ hybridizati on (FISH) to resolve the phenotype/genotype discrepancy in a patient w ith ambiguous genitalia in whom the peripheral blood karyotype was 45, X. Gonadectomy at age 7 months showed the gonadal tissue to be prepube rtal testis on the left side and a streak gonad on the right. The kary otype obtained from the left gonad was 45,X/46,XXq- and that from the right gonad was 45,X. Three different techniques, PCR amplification, F ISH, and chromosome painting for X and Y chromosomes, confirmed the pr esence of Y chromosome sequences. Five different tissues were evaluate d. The highest percentage of Y chromosome positive cells were detected in the left gonad, followed by the peripheral blood lymphocytes, skin fibroblasts, and buccal mucosa. No Y chromosomal material could be id entified in the right gonad, Since the Xq- chromosome is present in th e left gonad (testis), it is likely that the Xq- contains Y chromosoma l material. Sophisticated analysis in this patient showed that she has at least 2 cell lines, one of which contains Y chromosomal material. These techniques elucidated the molecular basis of the genital ambigui ty for this patient. When Y chromosome sequences are present in patien ts with Ullrich-Turner syndrome or gonadal dysgenesis, the risk for go nadal malignancy is significantly increased. Hence, molecular diagnost ic methods to ascertain for the presence of Y chromosome sequences may expedite the evaluation of patients with ambiguous genitalia. (C) 199 5 Wiley-Liss, Inc.