A novel A10E homozygous mutation in the HSD3B2 gene causing severe salt-wasting 3 beta-hydroxysteroid dehydrogenase deficiency in 46,XX and 46,XY French-Canadians: Evaluation of gonadal function after puberty

Severe 3 beta-hydroxysteroid dehydrogenase (S beta HSD) deficiency is a rar e form of congenital adrenal hyperplasia resulting from mutations in the HS D3B2 gene that impair steroidogenesis in both the adrenals and gonads and c ause salt-wasting in both sexes and incomplete masculinization of the exter nal genitalia in genetic males. About two thirds of the reported patients a re 46,XY. We describe two French-Canadian patients from two families withou t a known relationship who presented with severe salt-wasting 3 beta HSD de ficiency in infancy. Although the diagnosis was considered clinically, plas ma steroid profiles were confusing. We have thus directly sequenced DNA fra gments generated by PCR amplification of the four exons, exon-intron bounda ries, and the 5'-flanking regions of the HSD3B2 gene. Sequencing of exon II revealed the presence of a C to A transversion in both alleles of these tw o cases, thus converting codon 10 (GCA), which codes for Ala, into GAA, enc oding Glu. This Ala is highly conserved in the vertebrate 3 beta HSD gene f amily and is located in the putative NADbinding domain of the enzyme. The m utant type II 3 beta HSD enzyme carrying an A10E substitution exhibited no detectable activity in intact transfected Ad293 cells. Both homozygous pati ents share the same haplotype, spanning approximately 3.3 centimorgans surr ounding the HSD3B2 locus, which is consistent with a founder effect for thi s missense mutation. The 46,XY patient presented with ambiguous genitalia a t birth and underwent normal masculinization at puberty, but was azoospermi c at 18.5 yr of age. The 46,XX patient presented progressive breast develop ment, menarche, and evidence of progesterone secretion. The only previously reported cases with pubertal follow-up revealed paternity in one male and hypogonadism in one female. These findings demonstrate the complex relation ships between the genotype and the gonadal phenotype in severe 3 beta HSD d eficiency and the difficulty in predicting fertility.