The Clinical and Molecular Heterogeneity of 17βHSD-3 Enzyme Deficiency

17-β-Hydroxysteroid dehydrogenase type 3 (17βHSD-3) deficiency is a rare, but frequently misdiagnosed autosomal recessive cause of 46,XY disorder of sex development (DSD). 17βHSD-3 enzyme is present almost exclusively in the testes and converts Δ4-androstenedione (Δ4) to testosterone (T). The diagnosis can be easily missed in early childhood as the clinical presentation may be subtle. Any young girl with an inguinal hernia, mild clitoromegaly, single urethral opening or urogenital sinus should raise suspicion. If not diagnosed early, patients present with severe virilization and primary amenorrhea in adolescence and may undergo a change from a female to male gender role. A low T/Δ4 ratio on baseline or hCG (human chorionic gonadotropin)-stimulated testing is suggestive of 17βHSD-3 deficiency. The diagnosis can be confirmed with molecular genetic studies. This review summarizes the clinical presentations, reported mutations, diagnosis, treatment and clinical course of this disorder. The Arg80 site in exon 3 is the most common location of repeated mutations and can be considered a hot spot in certain Arab populations.