Testicular failure must have occurred after the onset of formation of Mullerian-inhibiting substance and before the initiation of testosterone synthesis; that is, after Sertoli cell development, but before the onset of Leydig cell function. In others, testicular failure must occur later in gestation, and these individuals may constitute problems in gender assignment. Some have incomplete Mullerian regression, but none has normal Mullerian development. At the final extreme is the syndrome of bilateral anorchia in which phenotypic men have an absence of Mullerian structures and gonads but a male Wolffian system and male external genitalia (Fig. 11.25). The pathogenesis is not understood. Management depends on the phenotype.
