SRXY11 is characterized by a genital phenotype that may range from predominantly female to predominantly male, including marked sex ambiguity depending on the duration of normal testicular function prior to the loss of testicular tissue. Approximately half of patients present with micropenis and bilateral cryptorchidism, and half present with female-appearing or ambiguous external genitalia (da Silva et al., 2019; McElreavey et al., 2020). The testicular regression syndrome (TRS) was delineated by Sarto and Opitz (1973), who called it the XY gonadal dysgenesis syndrome. It is characterized primarily by the absence of gonads in an XY person. In most cases, uterus and fallopian tubes are absent but small tubular structures interpreted as mullerian or wolffian rudiments (or both) are present. The range of virilizing effects due to early testicular tissue extends from none in phenotypic females with only slightly hypoplastic normal external genitalia, well-formed but hypoplastic uterus, and well-formed tubes (De Marchi et al., 1981) to the anorchic phenotypic male (Edman et al., 1977). Most affected individuals lack a vagina but a urogenital sinus or pseudovaginal urethral outpouching is found. Partial labioscrotal fusion and clitoris enlargement are common, breast development is absent, and postpubertal eunuchoid habitus is the rule. Sometimes nongenital anomalies are present (summary by Rosenberg et al., 1984).

Sex reversal in an individual with 46,XY karyotype caused by point mutations or deletions in the SRY gene, encoding sex-determining region Y protein.