Background: The diagnosis of 46,XY disorder of sex development (DSD) due to 5-alpha reductase 2 (5α-RD2) deficiency has been based on testosterone:dihydrotestosterone (T:DHT) ratio, urinary steroid profiling and mutational analysis of SRD5A2 gene. The biochemical hallmarks of 5α-RD2 deficiency include increased T:DHT ratio. However, several difficulties are observed in the DHT measurement leading to misdiagnosis. The mutational analysis of the SRD5A2 has been proposed as the first line test in the investigation of 5α-RD2 deficiency.
Objective: To screen SRD5A2 for mutation in 21 patients divided in two groups: group 1: six patients with known T:DHT ratio (range from 11 to 129) and group 2: 15 referred patients without T:DHT ratio, 13 of them previously orchiectomized.
Methodology: PCR was used to amplify the SRD5A2 followed by sequencing. The variants were analyzed by PolyPhen and SIFT prediction websites. SRD5A2 CNVs was evaluated by MLPA technique.
Results: In group I, four allelic variants were identified in homozygous state, two novel variants, p.Trp140Glnfs*19 and p.Gly123Val, both predict as potentially damage. The variant p.Trp140Glnfs*19 was found in two unrelated patients with T:DHT ratio of 11 and 43. The patient homozygous for p.Gly123Val mutation had T:DHT ratio of 24. The p.Arg227* and p.Gln126Arg mutations were found in two patients with T/DHT ratio of 46 and 129. In another patient with T:DHT ratio of 39, the heterozygous variants, p.Val89Leu (damage) and p.Asp164Val (benign) were identified. SRD5A2 CNV was not identified in this patient. From group 2, one patient, previously gonadectomized, is homozygous for p.Gly183Ser mutation.
Conclusion: SRD5A2 sequencing identified mutations or potential deleterious allelic variants in 100% of patients with hormonal profile of 5α-RD2 deficiency and in two patients with normal or unavailable T:DHT ratio. Sequencing of SRD5A2 is a fast and effortless technique and should be used as the preferable approach for the diagnosis of 46,XY DSD due to 5α-RD2 deficiency.
20 - 22 Sep 2014
European Society for Paediatric Endocrinology