QUIZ: No. 19

Diagnosis: Complete Androgen Insensitivity Syndrome (CAIS)

Findings:

Ultrasound demonstrates absence of the uterus and ovaries within the pelvis. MRI pelvis shows complete absence of Müllerian duct structures, including the uterus, cervix, and upper vagina.  A short blind-ending vaginal pouch is identified.  Bilateral oval gonadal structures are seen along the pelvic sidewalls/inguinal regions, showing signal characteristics consistent with testes. No ovarian tissue is identified.  Urinary bladder appears normal. No associated pelvic mass or lymphadenopathy is seen.

Discussion:

• Complete androgen insensitivity syndrome is an X-linked disorder caused by mutations of the androgen receptor gene, resulting in complete resistance of peripheral tissues to androgens.

• Affected individuals have a 46, XY karyotype and functioning testes that produce testosterone and anti-Müllerian hormone (AMH).

• AMH causes regression of Müllerian structures, leading to absence of the uterus, fallopian tubes, and upper vagina.

• Despite normal or elevated testosterone levels, target tissues are unable to respond to androgens, resulting in a phenotypic female appearance.

• Patients typically present during adolescence with primary amenorrhea, normal breast development, sparse pubic and axillary hair, and a blind-ending vagina.

• MRI is the imaging modality of choice for demonstrating absent Müllerian structures and locating undescended testes.

Teaching Pearl:

In a phenotypic female with primary amenorrhea, absence of the uterus, a blind-ending vagina, and bilateral pelvic or inguinal testes is highly suggestive of Complete Androgen Insensitivity Syndrome (46, XY Disorder of Sex Development).