✅ Model Answer:
• Diagnosis: Complete androgen insensitivity syndrome (CAIS) – 46,XY DSD.
• Evidence: 46,XY, female phenotype, primary amenorrhea, blind vaginal pouch, absent uterus, inguinal testes, elevated testosterone with elevated LH (androgen resistance), elevated estradiol from peripheral aromatization.
• Next step: Gonadectomy after puberty (age 16-18) to prevent malignancy (risk of germ cell tumor ~5-10%), then lifelong estrogen replacement. Genetic counseling for family (X-linked recessive). Multidisciplinary care (endocrinology, psychology, gynecology).

✅ Model Answer:
• Gene: AR (androgen receptor) located on chromosome Xq11-12.
• Inheritance: X-linked recessive (males are affected; females are carriers).
• Prevalence: 1 in 20,000-64,000 male births (most common cause of 46,XY DSD).
• Pathophysiology: Mutations in the AR gene lead to complete or partial resistance to androgens (testosterone and DHT). In CAIS, the receptor is completely non-functional → androgen signaling is absent → female phenotype despite 46,XY karyotype.
• Testes: Produce normal testosterone and AMH – Müllerian structures regress (no uterus), Wolffian structures do not develop (no epididymis, vas deferens).
• Most common mutation: Various (missense, nonsense, frameshift, deletion) – over 1,000 mutations reported.

✅ Model Answer:
• Classic features:
- Female external genitalia: Normal female phenotype at birth (often diagnosed at puberty).
- Primary amenorrhea.
- Blind vaginal pouch: Short, blind-ending vagina (no uterus or cervix).
- Absent or scanty pubic/axillary hair (androgen resistance).
- Breast development: Normal or enhanced (due to peripheral aromatization of testosterone to estradiol).
- Inguinal testes: Testes may be palpable in the inguinal canal or labia (10-20% risk of hernia).
- Tall stature.
• Other features:
- Normal female gender identity.
- No Müllerian structures (no uterus, fallopian tubes).
- No Wolffian structures (epididymis, vas deferens).
- Risk of gonadal malignancy: Increased after puberty (germ cell tumors – seminoma, gonadoblastoma).

✅ Model Answer:
• Karyotype: 46,XY (essential).
• Hormonal studies:
- Testosterone: Normal to high (male range).
- DHT: Normal (differentiates from 5α-reductase deficiency).
- LH: Elevated (due to lack of negative feedback).
- FSH: Normal or mildly elevated.
- Estradiol: Elevated (due to peripheral aromatization).
- AMH: Normal (testes are functional).
- Inhibin B: Normal.
• Pelvic ultrasound/MRI: Absent uterus, inguinal or abdominal testes.
• Genetic testing: AR gene sequencing (confirmatory).
• Androgen binding assay: In fibroblasts (confirms receptor defect – rarely done now).
• Family history: X-linked pattern (maternal uncles may be affected).

✅ Model Answer:
• Gonadectomy:
- Timing: After puberty (usually age 16-18), once breast development is complete.
- Reason: Prevent gonadal malignancy (risk increases with age; 5-10% risk).
- Laparoscopy: Removal of intra-abdominal or inguinal testes.
• Estrogen replacement therapy:
- Start after gonadectomy: Transdermal or oral estradiol (to maintain female secondary sexual characteristics and bone health).
- Dose: 0.025-0.1 mg/day (transdermal) or 1-2 mg/day (oral).
- Add progesterone: Cyclical progesterone to protect endometrium (if uterus is absent, may not be needed).
• Psychosocial support:
- Disclosure: Careful counseling about diagnosis, karyotype, and fertility.
- Support groups.
• Vaginal dilation: If needed for sexual function (vaginal hypoplasia).
• Bone density monitoring: Ensure adequate estrogen for bone health.

✅ Model Answer:
• Gonadal malignancy:
- Risk: 5-10% (especially seminoma, gonadoblastoma).
- Risk increases: With age (especially after puberty).
- Prevention: Gonadectomy.
• Infertility: No uterus → inability to carry pregnancy (but eggs can be harvested before gonadectomy for surrogacy).
• Vaginal hypoplasia: May require dilation or surgical vaginoplasty.
• Osteoporosis: If estrogen replacement is inadequate.
• Psychosocial: Gender identity, body image, coping with karyotype.
• Hernia: Inguinal hernia containing testes (may present in infancy).

✅ Model Answer:
• Prognosis:
- Excellent with appropriate management.
- Gender identity: Usually female (consistent with sex of rearing).
- Quality of life: Good with multidisciplinary care.
- Fertility: Can have children via surrogacy (oocyte retrieval before gonadectomy).
- Life expectancy: Normal.
• Long-term follow-up:
- Monitor estrogen levels and bone density.
- Monitor for late complications.
- Psychosocial support.
- Genetic counseling: X-linked recessive (carrier testing for female relatives).

✅ Model Answer:
• CAIS (Complete Androgen Insensitivity):
- Karyotype: 46,XY.
- Gonads: Testes (inguinal or abdominal).
- Hormones: High testosterone, high LH, normal AMH.
- Breast development: Present (due to aromatization).
- Pubic/axillary hair: Sparse or absent.
- Uterus: Absent (Müllerian regression).
- Risk: Gonadal malignancy (requires gonadectomy).
- Inheritance: X-linked recessive.
• MRKH syndrome (Mayer-Rokitansky-Küster-Hauser):
- Karyotype: 46,XX.
- Gonads: Normal ovaries.
- Hormones: Normal female levels (no androgen excess).
- Breast development: Present (normal puberty).
- Pubic/axillary hair: Normal.
- Uterus: Absent (Müllerian agenesis).
- Risk: No gonadal malignancy.
- Inheritance: Sporadic (autosomal dominant with incomplete penetrance).