True hermaphroditism: a clinical description and a proposed function for the long arm of the Y chromosome.

True hermaphroditism is a very rare form of ambiguous genitalia characterized by the presence of both ovarian and testicular tissue in the same individual. Sixty percent of these patients have a 46,XX karyotype; however, most have H-Y antigen detectable. Since H-Y antigen is thought to be the gene product of the short arm of the Y, then the short arm must be present somewhere in the karyotype. Products of the short arm loci are thought to initiate testicular differentiation and male determination. The long arm of the Y has not been detected in true hermaphrodites. Testicular histology in true hermaphrodites is characterized by spermatogenic arrest, causing us to speculate that the long arm of the Y might be essential for germ cell maturation beyond the spermatogonia state.