5α-Reductase 2 deficiency (5αR2D) is an autosomal recessive condition caused by mutations impairing the function of SRD5A2, a gene located on chromosome 2 and encoding the enzyme 5α-reductase type 2 (5αR2). 5αR2 is expressed in specific tissues and catalyzes the transformation of testosterone (T) to 5α-dihydrotestosterone (DHT). DHT plays a key role in the process of sexual differentiation.