MON-066 17B-hydroxysteroid dehydrogenase Type 3 Deficiency: An Under-Recognized Cause of 46,XY DSD in the United States?

Abstract

Title: 17β-hydroxysteroid dehydrogenase type 3 deficiency: An under-recognized cause of 46,XY DSD in the United States? Introduction: The 17β-hydroxysteroid dehydrogenase type 3 (17BHSD3) enzyme, expressed in the testes, converts androstenedione (A) to testosterone (T). 17BHSD3 deficiency causes a 46,XY difference of sex development (DSD), or intersex condition, characterized by lack of prenatal virilization followed by marked virilization at puberty due to peripheral conversation of A to T by other 17BHSD isoenzymes. Diagnosis is suspected with an abnormal T:A ratio of <0.8 and confirmed by HSD17B3 sequencing and deletion/duplication analysis. 17BHSD3 deficiency may present similarly to complete or partial androgen insensitivity syndrome (CAIS, PAIS) due to undervirilization in infancy, and to 5α-reductase deficiency due to virilization during puberty. Previously, only 12 cases of this autosomal recessive disorder have been reported in the US. We report 3 cases of 17BHSD3 deficiency diagnosed at a single pediatric center in the US. Clinical Cases: Patient A had atypical genitalia at birth and a presumed diagnosis of PAIS though sequencing of AR was normal. He underwent multiple genital surgeries throughout childhood, had significant psychiatric and behavioral concerns, and was referred to our multidisciplinary clinic at age 16 years. Additional diagnostic testing revealed a T:A ratio of 0.29 consistent with 17BHSD3 deficiency; confirmatory genetic testing was deferred per family preference.Patient B was noted to have testicular tissue present at age 3 years during an inguinal hernia repair and was diagnosed with CAIS. She presented to our institution at age 14 years with clitoromegaly. T:A ratio was 0.29 and genetic testing revealed a pathogenic splice site variant in HSD17B3. She requested gonadectomy due to unwanted virilization inconsistent with her female gender identity. Following gonadectomy at age 16 years, she began estrogen treatment and vaginal dilations.Patient C presented to our institution at age 18 years with pubertal delay and primary amenorrhea. She was noted to have palpable gonads and clitoromegaly. Evaluation revealed a 46,XY karyotype and a T:A ratio of 0.32. She was raised as a girl and identified as female. She requested gonadectomy to avoid further virilization, after which she began estrogen for pubertal induction. She deferred confirmatory genetic testing. Conclusions: Previous studies noted 17BHSD3 deficiency to be rare in the US, but the presence of 2 suspected and 1 confirmed diagnoses at a single US institution suggests it is likely more common and may be misdiagnosed as other types of DSD. Differentiating 17BHSD3 deficiency from other causes of 46,XY DSD is essential to inform accurate counseling about sex designation, gender identity, gonadal function, malignancy risk, potential fertility and heritability.