<unk>  <unk> R2D) is an autosomal recessive condition caused by a mutation in SRD5A2, a gene encoding the enzyme<unk> -reductase type 2 <unk> R2). The condition is rare, affects only genetic males, and has a broad spectrum of presentations, most apparent in the genitalia where a male is born with an underdeveloped penis that might develop to various extents in puberty and hence be "raised as female" up to a certain age.<unk> R2 is expressed in specific tissues and catalyzes the transformation of testosterone (T) to<unk> -dihydrotestosterone (DHT). DHT plays a key role in the process of sexual differentiation in the external genitalia and prostate during development of the male fetus.<unk> R2D is a result of impaired<unk> R2 activity resulting in decreased DHT levels. This defect results in a spectrum of phenotypes including overt genital ambiguity, female appearing genitalia, hypospadias, penile urethra, and isolated micropenis. Affected males still develop typical masculine features at puberty (deep voice, facial hair, muscle bulk) since most aspects of pubertal virilization are driven by testosterone, not DHT. Management of this condition in the context of sex assignment is a challenging and controversial area. Diagnostic availability, local laws, parental anxiety all play roles in treatment decisions. The investigation of<unk> R2D as a disease has played a key role in the biochemical characterization of the SRD5A2 gene, the<unk> R2 enzyme, and DHT in male sexual differentiation.
5α-Reductase 2 deficiency
Isolated 17,20-lyase deficiency
17β-Hydroxysteroid dehydrogenase III deficiency
Aromatase deficiency
Cortisone reductase deficiency
Androgen-induced hermaphroditism
Multiple sulfatase deficiency
Gonadotropin-releasing hormone insensitivity