Persistence of Müllerian ducts in male pseudohermaphroditism, and its relationship to cryptorchidism.

Twenty-two cases of male pseudohermaphroditism with persistence of Müllerian duct derivatives were reviewed. In 12 cases of mixed gonadal dysgenesis and five cases of dysgenetic male pseudohermaphroditism, testosterone-dependent steps of sex differentiation were also impaired, and testicular dysgenesis was prominent, even in the younger age group. The capacity of testes to inhibit the ipsilateral Müllerian duct was correlated with testicular descent: it is suggested that testicular dysgenesis explains both the functional and topographical testicular abnormalities observed in these male pseudohermaphrodites. Five other patients were cryptorchid but externally normally virilised, persistence of Müllerian derivatives representing their only abnormality of sex differentiation. Testicular structure was usually normal or showed changes attributable to long-standing cryptorchidism. It is suggested that in these patients, persistence of Müllerian derivatives is due to an inborn error of metabolism, affecting the binding of anti-Müllerian hormone to its receptor and that failure of testicular descent is caused by mechanical restraint by the abdominal Müllerian organs.