Identification of a novel mutation in the SRD5A2 gene of one patient with 46,XY disorder of sex development

Mutational analysis of compound heterozygous mutation p.Q6X/p.H232R in SRD5A2 causing 46,XY disorder of sex development

Background

Over 100 mutations in the SRD5A2 gene have been identified in subjects with 46,XY disorder of sex development (DSD). Exploration of SRD5A2 mutations and elucidation of the molecular mechanisms behind their effects should reveal the functions of the domains of the 5α-reductase 2 enzyme and identify the cause of 46,XY DSD. Previously, we reported a novel compound heterozygous p.Q6X/p.H232R mutation of the SRD5A2 gene in a case with 46,XY DSD. Whether the compound heterozygous p.Q6X/p.H232R mutation in this gene causes 46,XY DSD requires further exploration.

Methods

The two 46,XY DSD cases were identified and sequenced. In order to identify the source of the compound heterozygous p.Q6X/p.H232R mutation, the parents, maternal grandparents, and maternal uncle were sequenced. Since p.Q6X mutation is a nonsense mutation, p.H232R mutation was transfected into HEK293 cells and dihydrotestosterone (DHT) production were analyzed by liquid chromatography–mass spectrometry (LC–MS) for 5α-reductase 2 enzyme activities test. Apparent michaelis constant (Km) were measured of p.H232R mutation to analyze the binding ability change of 5α-reductase 2 enzyme with testosterone (T) or NADPH.

Results

The sequence results showed that the two 46,XY DSD cases were the compound heterozygous p.Q6X/p.H232R mutation, of which the heterozygous p.Q6X mutation originating from maternal family and heterozygous p.H232R mutation originating from the paternal family. The function analysis confirmed that p.H232R variant decreased the DHT production by LC–MS test. The Km analysis demonstrated that p.H232R mutation affected the binding of SRD5A2 with T or NADPH.

Conclusions

Our findings confirmed that the compound heterozygous p.Q6X/p.H232R mutation in the SRD5A2 gene is the cause of 46,XY DSD. p.H232R mutation reduced DHT production while attenuating the catalytic efficiency of the 5α-reductase 2 enzyme.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13052-022-01243-4.

Rupture and hemorrhage of a seminoma mixed with yolk sac tumors in 46XY partial gonadal dysgenesis: a case report and literature review

Background

46XY partial gonadal dysgenesis (PGD) is a rare subtype of disorder of sex development (DSD). 46YY PGD is a congenital disease with atypical chromosomal, gonadal, or anatomical sex development. The patient in this case report had male and female genitalia simultaneously. We created a flowchart of the differential diagnosis for clinicians.

Case presentation

A 41-year-old male was admitted to the hospital complaining of lower quadrant abdominal pain for 1 day. Physical examination revealed that his penis size was normal, but a urethral orifice was located in the perineum area between the scrotum and anus. One small testicle was in the left scrotum, but no testicle was present on the right. The patient’s abdomen was bulging, and he had lower abdominal pain. According to the emergency CT scan, a lesion (74*65 mm) was found in the right pelvis between the bladder and rectum. The lesion showed an unclear boundary and hematocele appearance. The lesion was removed by emergency surgery, and the pathology report indicated a mixed germ cell tumor with a seminoma and yolk sac tumors.

Conclusion

This article is a case report of germ cell tumors in 46XY PGD patients. The literature review summarizes the clinical diagnosis, and a flowchart is provided for physicians in future practice. The importance of this report is that it will help acquaint physicians with this rare disease and make the right initial clinical decision quickly through the use of this flowchart. However, the variants of special subtypes of 46XY DSD are myriad, and all the diagnoses could not be covered in one flowchart.