A novel SRD5A2 mutation in a Taiwanese newborn with ambiguous genitalia

The 5α-reductase type 2 deficiency is a rare autosomal recessive 46,XY disorder of sex development caused by the mutated 5α-reductase type 2 (SRD5A2) gene. In this disease, defective conversion of testosterone to dihydrotestosterone leads to variable presentations of male ambiguous genitalia during fetal development. The most crucial clinical decision for the affected individual is proper gender assignment; therefore, a prompt and correct diagnosis is important. In this present study, we report a normal male karyotype manifesting microphallus, bifid scrotum/labia majora with bilateral palpable gonads, and a blind-ended pseudovagina. The mutation analysis of the SRD5A2 gene revealed one novel C to T transition changing glutamine to a stop codon at codon 71 (p.Q71X) in exon 1 and one known G to A transition changing arginine to glutamine at codon 227 (p.R227Q) in exon 4. The p.Q71X mutation presumably results in a truncated protein, while the p.R227Q mutation is conceived to impair enzyme function and has been reported in patients of East Asian descent. This report demonstrates the essential role of hormonal and molecular studies for genetic counseling and gender assignment in males with pseudovaginal disorder of sex development, and our report helps identify a novel SRD5A2 gene mutation in the Taiwanese population.