5 alpha reductase enzyme deficiency

 The presentation of primary amenorrhea with virilisation, clitoromegaly, blind-ended vagina, and Tanner stage 2 pubic hair development, alongside a 46 XY genotype, suggests 5-alpha reductase deficiency.  

Definition:  

5-alpha reductase deficiency is a condition with a deficiency in the enzyme 5-alpha reductase, which converts testosterone to dihydrotestosterone (DHT).  

Features:  

DHT is crucial for the development of male external genitalia.  

Individuals with this deficiency typically have normal testosterone levels because the enzyme defect doesn't affect testosterone production.  

At birth, they are often assigned female because they have ambiguous genitalia or appear female externally. 

• ​During puberty, testosterone levels increase, leading to virilization (e.g., clitoromegaly).

• ​They usually have a blind-ending vagina and often prepubertal breast development because DHT is important for male genital development but not for pubic hair development, which relies on testosterone.