In a 46,XY patient with female external genitalia at birth and virilization at puberty, the combination of primary amenorrhea, lack of breast development, clitoromegaly, normal pubic hair development, CAUV, and high T level prompt the diagnosis of SRD5A2 deficiency [51]. The gene discussed is SRD5A2; the disease is hyperinsulinemic hypoglycemia, familial, 4.