5-α reductase deficiency

Pathogenesis

• 46,XY genotype
• Impaired conversion of testosterone to DHT
• Impaired virilization during embryogenesis
• Normal male testosterone & estrogen levels

Clinical features

• Male internal genitalia (eg, testes, vas deferens)
• Female external genitalia (eg, blind-ending vagina)
• Phenotypically female at birth
• Virilization at puberty (↑ testosterone)
  • Clitoromegaly
  • Increased muscle mass
  • Male pattern hair development
  • Nodulocystic acne

DHT = dihydrotestosterone.