MUTATION IN THE HUMAN GENE FOR 3-BETA-HYDROXYSTEROID DEHYDROGENASE TYPE-II LEADING TO MALE PSEUDOHERMAPHRODITISM WITHOUT SALT LOSS

A 5-year-old XY pseudohermaphrodite was found to have a defect of ster oid biosynthesis consistent with a partial deficiency of the enzyme 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD). Circulating concentrat ions of Delta(5) steroids and Delta(5) urinary steroid metabolites wer e elevated and remained elevated after orchidectomy. There was no evid ence of salt loss, plasma renin being within normal limits, and no det ectable glucocorticoid abnormality. The coding sequences of the genes for 3 beta-HSD types I and II were amplified by PCR and screened for m utations by denaturing gradient gel electrophoresis (DGGE) and manual and automatic DNA sequencing. A mutation in the gene for 3 beta-HSD ty pe II was observed at codon 173 (CTA-->CGA), leading in the affected p atient to a homozygous substitution in which the leucine at residue 17 3 was altered to an arginine (L173R). The propositus's 2-year-old XX s ister was also homozygous for L173R and showed the biochemical charact eristics of partial 3 beta-HSD deficiency without clinical symptoms or signs. The mutation segregated as an autosomal recessive. Three relat ed heterozygous adult females showed evidence of a small overproductio n of Delta(5) steroids and steroid metabolites and a variable reductio n in ovarian function. Concentrations of Delta(5) steroids and steroid metabolites in the heterozygous father of the propositus were within the normal range. These data are discussed in relation to the endocrin e causes of pseudohermaphroditism and hirsutism. Evidence for tight li nkage between the genes for 3 beta-HSD types I and II was obtained usi ng a microsatellite polymorphism in the third intron of the gene for 3 beta-HSD type II and synonymous and non-synonymous mutations and poly morphisms in the gene for 3 beta-HSD type I. The latter polymorphisms were located 88 bp apart at the 3' end of the type I coding sequence a nd could be physically resolved as haplotypes using DGGE. The applicat ion of DGGE to the analysis of mutations in members of a multigene fam ily is discussed.