Two SRY-negative XX male brothers without genital ambiguity.

We report a Mexican family in which two sibs were identified as "classic" XX males without genital ambiguities. Molecular studies revealed that both patients were negative for several Y sequences, including SRY. A review of familial cases disclosed that this is the first family where a complete male phenotype was observed in Y-negative XX male non-twin brothers. These data suggest that an inherited loss-of-function mutation, in a gene participating in the sex-determining cascade, can induce normal male sexual differentiation in the absence of SRY.