Androgen insensitivity syndrome

Other Names: AIS; Testicular feminization syndrome (formerly); DHTR deficiency; Androgen receptor deficiency; Dihydrotestosterone receptor deficiency

Androgen insensitivity syndrome is a condition that affects sexual development before birth and during puberty.

People with this condition are genetically male, with one X chromosome and one Y chromosome in each cell. Because their bodies are unable to respond to certain male sex hormones (called androgens), they may have mostly female external sex characteristics or signs of both male and female sexual development.

Epidemiology

Complete androgen insensitivity syndrome affects 2 to 5 per 100,000 people who are genetically male. Partial androgen insensitivity is thought to be at least as common as complete androgen insensitivity. Mild androgen insensitivity is much less common.

Cause

Mutations in the AR gene cause androgen insensitivity syndrome. This gene provides instructions for making a protein called an androgen receptor. Androgen receptors allow cells to respond to androgens, which are hormones (such as testosterone) that direct male sexual development. Androgens and androgen receptors also have other important functions in both males and females, such as regulating hair growth and sex drive. Mutations in the AR gene prevent androgen receptors from working properly, which makes cells less responsive to androgens or prevents cells from using these hormones at all. Depending on the level of androgen insensitivity, an affected person's sex characteristics can vary from mostly female to mostly male.

Inheritance

X-linked recessive inheritance

This condition is inherited in an X-linked recessive pattern. A condition is considered X-linked if the mutated gene that causes the disorder is located on the X chromosome, one of the two sex chromosomes in each cell. In genetic males (who have only one X chromosome), one altered copy of the gene in each cell is sufficient to cause the condition. In genetic females (who have two X chromosomes), a mutation must be present in both copies of the gene to cause the disorder. Males are affected by X-linked recessive disorders much more frequently than females.

About two-thirds of all cases of androgen insensitivity syndrome are inherited from mothers who carry an altered copy of the AR gene on one of their two X chromosomes. The remaining cases result from a new mutation that can occur in the mother's egg cell before the child is conceived or during early fetal development.

Signs and symptoms

Complete androgen insensitivity syndrome occurs when the body cannot use androgens at all. People with this form of the condition have the external sex characteristics of females, but do not have a uterus and therefore do not menstruate and are unable to conceive a child (infertile). They are typically raised as females and have a female gender identity. Affected individuals have male internal sex organs (testes) that are undescended, which means they are abnormally located in the pelvis or abdomen. Undescended testes have a small chance of becoming cancerous later in life if they are not surgically removed. People with complete androgen insensitivity syndrome also have sparse or absent hair in the pubic area and under the arms.

The partial and mild forms of androgen insensitivity syndrome result when the body's tissues are partially sensitive to the effects of androgens. People with partial androgen insensitivity (also called Reifenstein syndrome) can have genitalia that look typically female, genitalia that have both male and female characteristics, or genitalia that look typically male. They may be raised as males or as females and may have a male or a female gender identity. People with mild androgen insensitivity are born with male sex characteristics, but they are often infertile and tend to experience breast enlargement at puberty.

For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed.

80%-99% of people have these symptoms

• Absent axillary hair
• Absent pubic hair
• Ambiguous genitalia, male(Ambiguous genitalia in males)
• Aplasia/Hypoplasia of the fallopian tube(Absent/small fallopian tube)
• Aplasia/hypoplasia of the uterus(Absent/small uterus)
• Cryptorchidism(Undescended testes)
• Delayed puberty(Delayed pubertal development)
• Male infertility
• Male pseudohermaphroditism
• Sparse axillary hair(Limited armpit hair)
• Sparse pubic hair(Decreased sexual hair)

30%-79% of people have these symptoms

• Inguinal hernia

5%-29% of people have these symptoms

• Testicular neoplasm(Testicular tumor)

Diagnosis

Complete AIS is rarely discovered during childhood. Sometimes, a growth is felt in the abdomen or groin that turns out to be a testicle when it is explored with surgery. Most people with this condition are not diagnosed until they do not get a menstrual period or they have trouble getting pregnant.

Partial AIS is often discovered during childhood because the person may have both male and female physical traits.

Tests used to diagnose this condition may include:

• Blood work to check levels of testosterone, luteinizing hormone (LH), and follicle-stimulating hormone (FSH)
• Genetic testing (karyotype) to determine the person's genetic makeup
• Pelvic ultrasound
• Other blood tests may be done to help tell the difference between AIS and androgen deficiency.

Treatment

• Testicles that are in the wrong place may not be removed until a child finishes growing and goes through puberty. At this time, the testes may be removed because they can develop cancer, just like any undescended testicle.
• Estrogen replacement is prescribed after puberty.
• Treatment and gender assignment can be a very complex issue, and must be targeted to each individual person

Prognosis

The outlook for complete AIS is good if the testicle tissue is removed at the right time. The outlook for partial AIS depends on the appearance of the genitals.

Possible Complications

Complications include:

• Infertility
• Psychological and social issues
• Testicular cancer

NIH genetic and rare disease info

• NIH info on Androgen insensitivity syndrome

Androgen insensitivity syndrome is a rare disease.

Androgen insensitivity syndrome Resources
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