A novel SRY nonsense mutation in a case of Swyer syndrome

Abstract

Swyer syndrome is a condition in which individuals with one X chromosome and one Y chromosome in each cell have a female appearance. They generally have female external genitalia, a normal uterus and Fallopian tubes, but no functional gonads. Its prevalence is about 1 in 30,000 births. Mutations in the SRY gene have been identified in 15-20% of the cases.

The authors present the clinical case of a female fetus, who was the first child of young, healthy, unrelated parents, with increased nuchal translucency in first trimester ultrasonography and combined risk for Down syndrome of 1/20. Prenatal karyotype was 46,XY. Delivery occured at 37 weeks gestation by cesarean section. Uneventful neonatal period. At birth she had adequate weight and height and presented complete female external genitalia with no other abnormalities. Pelvic ultrasound showed normal morphology of the uterus, ovaries were not visualized. Hormonal study was normal. Repeated postnatal karyotype confirmed 46,XY. Follow-up on Neonatology Consultation as outpatient. Abdomino-pelvic MRI (3 months old) showed presence of uterus with normal dimensions and appearance and ovaries not clearly defined. The molecular genetic testing revealed the Q 114X (c.340 C>T) mutation of the SRY gene, a nonsense mutation that as not been described.

Early diagnosis of Swyer syndrome in childhood is only possible if a karyotype is carried out for other reasons, such as for example as part of prenatal diagnosis (as it happened with our patient).

This prompt diagnosis is important for early institution of hormone replacement therapy and close monitoring, because of the risk of gonadal malignancy. Clinical and imaging surveillance is mandatory in order to program early gonadectomy if necessary. In our patient, the novel mutation detected in the SRY gene may be an aetiopathogenic factor in clinically defined 46,XY complete gonadal dysgenesis.