RESUMEN
We report the first known case of p450 oxidoreductase deficiency (PORD) in a Spanish boy who presented ambiguous genitalia at birth as a unique feature. He had palpable gonads in the inguinal canal and a normal 46,XY karyotype. Blood tests showed increased lanosterol and androgen precursors (17-OH-pregnenolone and 17-OH-progesterone) and low adrenal androgens (dehydroepiandrosterone and its sulfate). Blood pressure and serum electrolytes were normal. As he had low-testosterone response to human chorionic gonadotropin stimulation but responded to exogenous testosterone with phallic growth, male sex was assigned. Testosterone/dihydrotestosterone ratio and inhibin B were normal. Adrenal insufficiency was detected by corticotropin test. Hydrocortisone replacement treatment was administered. Congenital adrenal hyperplasia was ruled out and molecular analysis of POR gene showed the missense mutation p.Gly539Arg in compound heterozygosity located at splice acceptor site of intron 2 and the coding variant p.Gly80Arg. Surgery for cryptorchidism and hypospadias was performed.