Uniparental isodisomy of chromosome 1 unmasking an autosomal recessive 3-beta hydroxysteroid dehydrogenase type II-related congenital adrenal hyperplasia

Steroid 3-beta hydroxysteroid dehydrogenase type ii (3β-hsd2) deficiency is a rare autosomal recessive form of congenital adrenal hyperplasia (cah). we report the genetic basis of 3β-hsd2 deficiency arising from uniparental isodisomy (upd) of chromosome 1. we describe a term undervirilized male whose newborn screen indicated borderline cah. the patient presented on the 7th day of life in salt-wasting adrenal crisis. steroid hormone testing revealed a complex pattern suggestive of 3β-hsd deficiency. chromosomal microarray and single nucleotide polymorphism analysis revealed complete upd of chromosome 1. sanger sequencing of hsd3b2 revealed a previously described missense mutation,c.424g>a (p.e142k) in homozygous state,thus confirming the diagnosis of 3β-hsd2 deficiency. we provide evidence of the existence of an uncommon mechanism for hsd3b2 gene-related cah arising from upd of chromosome 1. © 2017 by turkish pediatric endocrinology and diabetes society.