Ring Y chromosome without mosaicism.

: A 53-year-old man with a short stocky build, mild mental retardation, gynecomastia and hypogonadism was found to have a small ring Y chromosome unassociated with mosaicism. The ring Y was represented by a minute portion of chromatin or sometimes paired dots which were no larger than the short arm of the normally expected Y. No brightly fluorescent segment of the ring Y was present nor was it observed elsewhere in the karyotype. A primary medical problem was severe osteoarthritis, necessitating bilateral hip arthroplasties. Plasma testosterone was markedly decreased and plasma gonadotropins were increased. Potency was improved following testosterone injections. We conclude that genes responsible for testicular differentiation, maleness and possibly height are located close to the centromere of the Y chromosome, possibly on both the short and long arm. We also conclude that multiple genes are required for a fully developed male phenotype and apparently some of these genes were deleted or not expressed in this patient.