17βHSD-3 enzyme deficiency due to novel mutations in the HSD17B3 gene diagnosed in a neonate

17-β-Hydroxysteroid dehydrogenase type 3 (17βHSD-3) is present almost exclusively in the testes, and converts androstenedione (A) to testosterone (T). 17βHSD-3 deficiency is rare. The diagnosis can be missed in early childhood as the clinical presentation may be subtle. The most frequent presentation of 17 HSD-3 deficiency is a 46,XY individual with female external genitalia, labial fusion and a blind ending vagina, with or without clitoromegaly. A low testosterone/androstenedion (T/A) ratio is suggestive of 17βHSD-3 deficiency, and such diagnosis can be confirmed with molecular genetic studies. A 12-day newborn was referred to our hospital because of palpable gonads in the labia majora. On physical examination, the baby had female external genitalia and palpable gonads in the labia majora. T/A ratio was 0.26 and the diagnosis was 17βHSD-3 deficiency, which was confirmed by the evidence of compound heterozygousity novel frameshift mutations in exon 9 and 10 of HSD17B3 gene.