A case with mosaic di-, tetra-, and octacentric ring Y chromosomes

A newborn female infant presented with abnormalities of the external genitalia including a 3 x 1 cm phallic structure, a perineal urethral opening, bifid scrotum, and a single urogenital opening. Peripheral blood karyotype was 45,X[81]/46,X,+r(Y)[19], however, there were no signs of Ullrich-Turner syndrome. High resolution G-banding as well as C- and Q-banding did not demonstrate any specific banding pattern or presence of heterochromatin on the ring. However, it was noticed that some of the rings were larger than others. FISH with a probe for Yq12 was negative in all metaphases studied. A Y-specific paint probe hybridized to the entire ring chromosome, confirming its origin. PCR analysis showed the presence of the SRY locus and of proximal Yq locus DYS271. Triple color FISH with probes for the Y centromere, DYZ5 (Yp), and all human telomeres showed the existence of different types of rings, some dicentric, some tetracentric, and some probably octacentric. Owing to the increased risk for gonadoblastoma, a surgical removal of the gonads was performed.