Complete androgen insensitivity syndrome caused by the c.2678C>T mutation in the androgen receptor gene: A case report

BACKGROUND

Androgen insensitivity syndrome is an X-linked recessive genetic disease caused by mutations in the androgen receptor gene (AR). However, the underlying molecular mechanisms for the majority of AR variants remain unclear. In this study, we identified a point variant in three patients with complete androgen insensitivity syndrome (CAIS), summarized the correlation analysis, and performed a literature review.

CASE SUMMARY

The proband was raised as a girl. In infancy, she was first referred to hospital with a right inguinal hernia. Ultrasonography revealed the absence of a uterus and ovaries, and a testis-like structure located at the inguinal canal. Further diagnostic workup detected a 46, XY karyotype, and fluorescence in situ hybridization analysis showed the presence of the SRY gene. Histological analysis revealed the excised tissue to be testicular. Twelve years later, she was admitted to our hospital with a lack of breast development. Her pubic hair and breasts were Tanner stage I. She had normal female external genitalia. Blood hormone tests showed normal testosterone levels, low estradiol levels, and high gonadotropin levels. Her two siblings underwent similar examinations, and all three had a rare hemizygous missense mutation in AR: c.2678C>T. In vitro functional analyses revealed decreased nuclear translocation in AR-c.2678C>T mutation cells.

CONCLUSION

This case of CAIS was caused by an AR variant (c.2678C>T). Functional studies showed impaired nuclear translocation ability of the mutant protein.

Complete Androgen Insensitivity Syndrome due to Mutations in the DNA-Binding Domain of the Human Androgen Receptor Gene

Androgen insensitivity syndrome (AIS) is an X-linked recessive disorder with a 46,XY karyotype caused by alterations in the androgen receptor (AR) gene. We have identified 2 mutations in the AR gene that resulted in complete androgen insensitivity syndrome (CAIS) in 2 unrelated cases. This study includes cytogenetics, hormonal, molecular, and bioinformatics analysis including sequencing of the SRY (sex-determining region Y) and AR genes. Mutational analysis in the first case of primary amenorrhea revealed a novel nucleotide substitution (IVS2-2A>G) in the second intron of the AR gene. The mutation is located in the acceptor splice site (2 nucleotides before exon 3) and caused skipping of exon 3 and formation of an abnormal protein. The second mutation (g. 98762_98764delTCT) was identified in a case of oligoamenorrhea and caused the deletion of 1 amino acid (p.∆Phe583). Both identified mutations were located in the conserved P-box region of the DNA-binding domain which is responsible for base-specific contacts with the DNA major groove. Furthermore, a hormonal imbalance was also noticed in both cases with high levels of gonadotropins like FSH and LH in both cases. The present study concluded that both identified AR mutations are predicted to either abolish or decrease the binding ability of the AR to androgen response elements of its downstream genes.