45,X/46,XY gonadal dysgenesis, 46,XX/46,XY chimerism (and variants), and 46,XX testicular and ovotesticular DSD

45,X/46,XY gonadal dysgenesis occurs in around 1.5/10,000 conceptions. The clinical phenotype is highly variable; and features of Turner syndrome may be found to a variable extent in both males and females with this condition. Due to its rarity and heterogeneous presentation, long-term outcome data are scarce and large multicenter studies are needed to obtain reliable data on growth and results of growth hormone therapy, cardiovascular problems and other affected organ systems. Management of gonads in individuals who have a 45,X/46,XY karyotype is complex and needs to take in to account both gonadal function and an estimate of the risk for development of a germ cell tumor. An Xp:Yp translocation containing SRY often underlies 46,XX testicular DSD, these cases typically present as infertile males. Other causes are mostly associated with an ambiguous genital phenotype and ovotesticular gonadal development. New mechanisms, based on the loss of suppression of the antagonistic testicular pathway have been identified recently and seem to underlie at least a number of cases. Management of all these conditions is complex and should be performed by a multidisciplinary DSD team