SRD5A2 and hyperinsulinemic hypoglycemia, familial, 4: Herein, we report the histological and immunohistochemical testicular analysis of a posptubertal patient with 5α-R2 deficiency; the diagnostic was considered in front of the clinical presentation, associated with a high T/DHT ratio, and confirmed by the genetic analysis, which revealed a homozyguous missense mutation in the SRD5A2 gene (c.344G > A; Gly115Asp).