The persistent Mullerian (paramesonephric) duct, or the uterine hernia, syndrome is a rare disorder of male sexual development. It is characterized by the persistence of the uterus, fallopian tubes and upper vagina in otherwise normally virilized boys. Despite the normal male genotype and the subsequent normal development of fetal testis, Mullerian structures do not regress due to failure in production or in response to the anti-Mullerian hormone. Since the secretion and action of testosterone is not affected, the Wolffian (mesonephric) duct derivatives and the external genitalia of the fetus progress in the normal male direction. An intersex condition is, therefore, not usually suspected but the malformation is incidentally detected during operative treatment of associated abnormalities such as inguinal hernia and undescended testis, generally in the first year of life.

The diagnosis of persistent Mullerian duct syndrome is often established when a uterus and/or fallopian tube is found along with undescended testis in a genotypically and phenotypically normal male child during repair of inguinal hernia. The relative risk of testicular tumor is not increased in patients with persistent Mullerian duct syndrome if orchiopexy is performed before two years of age. The aetiology of persistent Mullerian duct syndrome is poorly understood. Some studies suggest that inheritance which may be either X-linked or autosomal recessive with male sex limitation is a possible cause of the disorder. The observation that most cases of persistent Mullerian duct syndrome are bilateral is noteworthy. Anti-Mullerian hormone is secreted by the Sertoli cells of the fetal testis and acts ipsilaterally. The sensitivity of Mullerian duct to this hormone is present only during the ambisexual stage of the embryonic period.