Sex Chromosome Fragment in a Phenotypically Normal Female: Significance of Occult Y-related Material

The authors report a 15-year-old short, nonvirilized, prepubertal female whose peripheral karyotype revealed a mosaicism in which 62 percent of the cells had a karyotype of 45X, and the other 38 percent had a karyotype of 46X plus a small unidentified marker chromosome. Since the authors were unable to determine from the karyotype whether this marker was derived from an X or a Y chromosome and because of the high risk for neoplasia in abnormal gonads containing Y material, she underwent surgical exploration, with removal of gonadal tissue. Microscopic examination of the streak gonads revealed a mixture of dysgenetic ovarian and testicular type tissues. The presence of testicular-like tubules strongly implied the presence of Y material in the genotype. Review of the literature reveals at least 19 similar cases in which presumed sex chromosomal markers or fragments were found in phenotypically normal females. Because of the risk of gonadal neoplasia in patients with occult Y chromosomal material, gonadectomy is indicated when the origin of the marker chromosome is uncertain.