A Novel SRD5A2 Loss-of-Function Variant in a Chinese Child with 5α-Reductase type 2 Deficiency

Differences or disorders of sex development (DSD) represent a range of congenital conditions that lead to discrepancies among a person's sex chromosomes, gonads, and anatomical sex. Variants in the SRD5A2 gene can lead to 5-alpha-reductase type 2 (5α-RD2) deficiency, a condition within the DSD spectrum. Here, we report a case of 5α-RD2 deficiency in a Chinese child, resulting from a newly identified compound heterozygous variant in SRD5A2. The proband, a 2-month-old child assigned female at birth, was initially observed to have bilateral hypertrophy of the labial folds during routine child healthcare visits at a local hospital. An ultrasound scan revealed testicular structures on both sides of the labial folds. The testosterone (T)/dihydrotestosterone (DHT) ratio after stimulation was 37, consistent with 5α-RD2 deficiency. Whole-exome sequencing and copy number variation analysis identified a novel compound heterozygous variant in SRD5A2, consisting of a 175.06 Kb deletion (including exon 1) located at chr2:31802204-31977267 and a c.607G>A (p.G203S) point mutation. Cytogenetic analysis confirmed a 46,XY karyotype. This case highlights a previously unreported compound heterozygous variant in SRD5A2 associated with 5α-RD2 deficiency in a Chinese child.