Severe undervirilisation in a 46,XY case due to a novel mutation in HSD17B3 gene

17-β-hydroxysteroid dehydrogenase type 3 (17β-hsd3) is an important enzyme involved in the final steps of androgen synthesis and is required for the development of normal male external genitalia. 46,xy individuals with deficiency of this enzyme present a wide clinical spectrum from a female appearance of the external genitalia through ambiguous genitalia to a predominantly male genitalia with micropenis or hypospadias. this paper reports a one-year-old 46,xy patient with 17β-hsd3 deficiency who presented with female external genitalia and bilaterally palpable gonads in the inguinal region. the low t/δ4 ratio after human chorionic gonadotropin (hcg) stimulation suggested 17β-hsd3 deficiency. a homozygous mutation,c.761_762delag,was determined at the intron 9/exon 10 splice site of the hsd17b3 gene. to the best of our knowledge,this mutation has not been reported thus far,but its localization and type would imply a complete disruption of the 17β-hsd3 which may explain the phenotype of our patient. © journal of clinical research in pediatric endocrinology,published by galenos publishing.