17β-Hydroxysteroid dehydrogenase type 3 deficiency as a result of a homozygous 7 base pair deletion in 17βHSD3 gene

17-β-Hydroxysteroid dehydrogenase type 3 (17βHSD-3) converts Δ 4 androstenedione (A) to testosterone (T) in the testes. This enzyme plays a key role in androgen synthesis and it is essential for normal fetal development of male genitalia. 17βHSD-3 deficiency is a rare cause of 46,XY disorders of sexual development. Here, we report a 16-year-old 46,XY patient with 17βHSD-3 deficiency raised as a female and significantly virilized in puberty. A homozygous 7 base pair deletion on exon 10 was determined in HSD17B3 gene (c.777-783del-GATAACC). Our patient had one of the veryrare mutations, which was previously unencountered in Turkish patients with 17βHSD type 3, and she is the second reported case with this deletion.