Persistent Müllerian duct syndrome - a rare but important cause of male factor infertility.

Persistent Müllerian duct syndrome (PMDS) is a rare difference of sex development, characterized by the presence of Müllerian duct derivatives in 46,XY individuals with male-typical development. PMDS typically presents during childhood with features of cryptorchidism, inguinal hernia or transverse testicular ectopia. Untreated PMDS is associated with risks of infertility and malignancy. Infertility is common, arising from cryptorchidism, anatomical malformations (such as epididymal aplasia) or extrinsic compression of the ejaculatory duct by Müllerian structures. At the time of diagnosis, just one in five men with PMDS are reported to have conceived naturally. Preservation of fertility potential requires prompt diagnosis and management via a holistic patient-centred approach that addresses the underlying cause. With cryptorchidism, which is a common manifestation of PMDS, early orchidopexy is the key initial intervention. The input of fertility specialists and assisted reproductive techniques can further support successful conception. Beyond its effects on fertility, PMDS carries a risk of malignant transformation in the testes and Müllerian structures, warranting complex management with inclusion of a multi-disciplinary team and consideration of orchidopexy, orchidectomy, excision of Müllerian remnants and onward surveillance. Thus, although rare, PMDS is an important cause of male factor infertility that might be encountered by urologists. Preservation of fertility potential requires a high index of clinical suspicion and timely intervention. Raising awareness of PMDS among clinicians is crucial to improve its detection, advance its clinical management and provide a basis for future research.