5-alpha-reductase type 2 deficiency (5-ARD) is an autosomal recessive sex-limited condition resulting in the inability to convert testosterone to the more physiologically active dihydrotestosterone (DHT). Because DHT is required for the normal masculinization of the external genitalia in utero, genetic males with 5-alpha-reductase type 2 deficiency are born with ambiguous genitalia (ie. 46,XY disorder of sexual development (DSD)).
Patients with 5-alpha-reductase type 2 deficiency classically present with striking ambiguity of the genitalia, with a clitoral-like phallus, bifid scrotum, pseudovaginal perineoscrotal hypospadias, and a rudimentary prostate. Occasionally, patients can appear more masculinized; they may lack a separate vaginal opening, and have isolated penile hypospadias
or even a penile urethra.
The uterus and fallopian tubes are absent because of the normal secretion of the müllerian-inhibiting factor. Testes are intact and are usually found in the inguinal canal or scrotum; however, cryptorchidism is frequently described with testes occasionally located in the abdomen. Wolffian duct differentiation is normal with seminal vesicles, vasa differentia, epididymides, and ejaculatory ducts. The prostate is small, nonpalpable, and rudimentary in adulthood. Neither benign prostate hyperplasia (BPH) nor prostate cancer has been reported in these patients.