THU186 A Case Of 3beta-hydroxysteroid Dehydrogenase Type2 Deficiency Diagnosed By Whole Genome Sequencing In A Patient With Congenital Adrenal Hyperplasia

Disclosure: S. Chang: None. C. Kim: None. 3β-hydroxysteroid dehydrogenase type 2 deficiency (3βHSD2D) is a very rare type of congenital adrenal hyperplasia (CAH) caused by HSD3B2 gene mutations. The estimated prevalence is less than 0.5% of all CAH and less than 1/1,000,000 at birth. It is a disorder of impaired steroidogenesis and sex steroid deficiency characterized by variable degrees of salt wasting, hypoglycemia, male incomplete masculinization and female virilization. Some newborns with 3βHSD2D have increased level of 17-hydroxyprogesterone (17OHP) that clinicians misdiagnose them as having classic 21-hydroxylase deficiency. A male newborn was referred to our hospital for generalized hyperpigmentation. Laboratory test showed hyponatremia, hyperkalemia and hypoglycemia. Hormonal study showed high level of adrenocorticotropic hormone, 17OHP, progesterone, renin activity, dehydroepiandrosterone (DHEA), androstenedione and low level of aldosterone. Clinically diagnosing with CAH, we administered glucocorticoid and mineralocorticoid replacement. We performed PCR sequencing for CYP21A2 gene mutation to confirm 21 hydroxylase deficiency but revealed normal result. After follow-up for 17 years with replacement treatment, he happened to have the opportunity to perform whole genome sequencing. Whole genome sequencing allowed to detect two pathogenic mutations in the HSD3B2 gene, described in compound heterozygosity (p.Arg249Ter and c.-149_143-1766del). One mutation (c.-149_143-1766del) is inherited from his father and the mother was not done for gene study. While there have been less than 100 cases of 3βHSD2D reported worldwide, in our best knowledge, this is the first case of genetically confirmed 3βHSD2D in Korea. Presentation: Thursday, June 15, 2023