What is Androgen Insensitivity Syndrome

Androgen Insensitivity Syndrome (AIS) is a genetic condition where an individual, who is genetically male (XY chromosomes), is resistant to the effects of androgens (male hormones). This resistance prevents the typical development of male physical characteristics, leading to a spectrum of presentations ranging from external genitalia that appear female to genitalia that may appear ambiguous or male with impaired fertility.

What causes Androgen Insensitivity Syndrome?

Androgen Insensitivity Syndrome is caused by mutations in the AR gene, which provides instructions for making the androgen receptor. Because the body cannot effectively respond to androgens, the internal and external development of the reproductive system is altered. This condition is inherited in an X-linked recessive pattern, meaning it is passed from a mother who carries the gene mutation to her children.

How is Androgen Insensitivity Syndrome classified?

The severity of Androgen Insensitivity Syndrome is typically categorized into three clinical forms based on the degree of androgen receptor function:

• Complete Androgen Insensitivity Syndrome (CAIS): Individuals have external female genitalia and are typically raised as female; they do not have a uterus, fallopian tubes, or ovaries.


• Partial Androgen Insensitivity Syndrome (PAIS): This form presents with a wide range of genital appearance, varying from mostly female to mostly male, often with ambiguous genitalia at birth.


• Mild Androgen Insensitivity Syndrome (MAIS): Individuals have external male genitalia but may experience undervirilization, such as gynecomastia or infertility.

How common is Androgen Insensitivity Syndrome?

Androgen Insensitivity Syndrome is rare, with an estimated prevalence for the complete form (CAIS) ranging from 1 in 20,000 to 1 in 99,000 genetic males. Because the presentation varies so significantly, it is possible that many individuals with milder forms remain undiagnosed throughout their lives.

How does Androgen Insensitivity Syndrome differ from other conditions?

Unlike other disorders of sex development (DSDs) that involve chromosomal abnormalities (such as Klinefelter syndrome), Androgen Insensitivity Syndrome specifically involves a functional receptor issue in an XY individual. It is distinct because the testes usually develop normally and produce testosterone, but the body remains unable to utilize that testosterone to promote male development.

Next steps

• Consult with a pediatric endocrinologist or a clinical geneticist for formal testing and evaluation.


• Connect with the 3 members of the DiseaseMaps community who have shared their experiences with Androgen Insensitivity Syndrome.


• Seek support from organizations like the AIS-DSD Support Group to connect with others navigating similar medical journeys.

Medical disclaimer: This information is for educational purposes only and should not replace professional medical advice, diagnosis, or treatment.

References

• NIH Genetic and Rare Diseases Information Center (GARD): Androgen Insensitivity Syndrome


• Orphanet: Complete Androgen Insensitivity Syndrome (ORPHA:790)


• OMIM (Online Mendelian Inheritance in Man): Androgen Receptor Gene (AR)


• AIS-DSD Support Group (aisdsd.org)