46, XX true hermaphroditism associated with a terminal deletion of the short arm of the X chromosome

Testes are determined by the activity of the SRY gene product encoded by the Y chromosome. Mutations in SRY can lead to XY sex reversal (XY females) and the presence of the SRY gene in some XX individuals can lead either to complete (XX males) or incomplete (XX true hermaphrodites) sex reversal. Approximately 10% of XX true hermaphrodites contain a portion of the Y chromosome, including SRY, in their genome. The etiology of the remaining cases is unestablished but may be caused by mutations in other as yet unidentied sex determining genes downstream of SRY. Here we describe an SRY-negative true hermaphrodite with a 46,X,del(X)(p21.1-pter). The patient also presented with severe mental retardation, abnormal skin pigmentation and below average height. Histological examination of the gonad revealed bilateral ovotestis. We postulate that the Xp deletion has unmasked a recessive allele on the apparently normal X chromosome generating the intersex phenotype. This observation together with recent findings of certain XY females carrying duplications of Xp21.3 suggests that there may be a loci on Xp which acts as a switch in the testis/ovarian determination pathways.