✅ Model Answer:
• Diagnosis: Swyer syndrome (46,XY complete gonadal dysgenesis).
• Evidence: 46,XY karyotype, female external genitalia, no palpable gonads, streak gonads (no AMH, low testosterone), elevated gonadotropins (primary gonadal failure).
• Next step: Gonadectomy (high risk of gonadoblastoma), then estrogen replacement at puberty (age 11-12 years). Genetic testing (SRY, NR5A1, SOX9). Multidisciplinary care (psychology, gynecology).

✅ Model Answer:
• Most common cause: SRY gene mutation (located on Y chromosome) – ~15% of cases.
• Other genes: NR5A1 (SF1), SOX9, WT1, DHH, MAP3K1, DMRT1 – involved in testicular development.
• Inheritance: Usually sporadic (de novo SRY mutations); can be autosomal recessive or dominant depending on the gene.
• Pathophysiology: Defective testicular determination → dysgenetic gonads (streak gonads) that do not produce AMH or testosterone → female phenotype with no Müllerian or Wolffian development.
• Prevalence: Rare (1 in 80,000 live births).

✅ Model Answer:
• Neonatal:
- Female external genitalia: Normal female phenotype at birth (often not recognized).
- No palpable gonads.
- Normal female internal genitalia: Uterus, fallopian tubes are present (Müllerian structures develop because no AMH is produced).
• Adolescence:
- Primary amenorrhea.
- No pubertal development (no breast development, no pubic hair – due to lack of gonadal hormones).
- Tall stature (due to lack of sex hormone-mediated epiphyseal closure).
• Other features: May have Turner-like features (webbed neck, cubitus valgus) if associated with sex chromosome mosaicism (45,X/46,XY).

✅ Model Answer:
• Karyotype: 46,XY (essential for diagnosis).
• Hormonal studies:
- FSH/LH: Elevated (hypergonadotropic hypogonadism).
- Testosterone: Low (undetectable).
- AMH: Undetectable (no Sertoli cells).
- Estradiol: Low.
• Pelvic ultrasound/MRI:
- Streak gonads: Small, fibrotic gonads (may not be visible).
- Uterus and fallopian tubes: Present (Müllerian structures).
• Genetic testing: SRY, NR5A1, SOX9, WT1, DHH, MAP3K1 gene sequencing.
• Bone age: Delayed (in adolescence).
• Gonadal biopsy: Not routinely performed (streak gonads with fibrous tissue).

✅ Model Answer:
• Gonadectomy:
- Timing: Soon after diagnosis (to prevent malignancy – high risk of gonadoblastoma and dysgerminoma).
- Procedure: Laparoscopic removal of streak gonads.
- Risk: Gonadoblastoma in 30-40% by age 30 if not removed.
• Estrogen replacement therapy:
- Start: At age 11-12 years (to induce pubertal development).
- Transdermal or oral estradiol: Gradually increase to adult dose over 2-3 years.
- Add progesterone: Cyclical progesterone after 2-3 years (to protect endometrium).
• Psychosocial support:
- Disclosure: Careful counseling about diagnosis and karyotype.
- Fertility: Uterus is present – may consider egg donation and IVF.
• Bone density monitoring: Ensure adequate estrogen for bone health.

✅ Model Answer:
• Gonadal malignancy:
- Risk: 30-40% (gonadoblastoma, dysgerminoma, seminoma).
- Prevention: Prophylactic gonadectomy.
• Infertility: Streak gonads do not produce eggs; but uterus is present → can use egg donation + IVF.
• Osteoporosis: If estrogen replacement is inadequate.
• Psychosocial: Gender identity, body image, coping with 46,XY karyotype.
• Short stature: If associated with sex chromosome mosaicism (45,X/46,XY).
• Other: Associated with renal or cardiac anomalies (depending on genetic cause).

✅ Model Answer:
• Prognosis:
- Good with early gonadectomy and hormone replacement.
- Gender identity: Usually female (consistent with sex of rearing).
- Quality of life: Good with multidisciplinary care.
- Fertility: Possible with egg donation and IVF (uterus is present).
- Life expectancy: Normal.
• Long-term follow-up:
- Monitor estrogen levels and bone density.
- Monitor for complications.
- Psychosocial support.
- Genetic counseling.

✅ Model Answer:
• Swyer syndrome:
- Gonads: Streak gonads (no testicular tissue).
- AMH: Undetectable (no Sertoli cells).
- Testosterone: Low/undetectable.
- FSH/LH: Elevated (hypergonadotropic).
- Uterus: Present (Müllerian structures develop because no AMH).
- Breast development: Absent without estrogen replacement.
- Pubic/axillary hair: Absent or sparse.
- Malignancy risk: High (gonadoblastoma, dysgerminoma) – requires gonadectomy.
- Genetics: SRY mutation (most common).
• CAIS (Complete Androgen Insensitivity):
- Gonads: Testes (inguinal or abdominal).
- AMH: Normal (Sertoli cells present).
- Testosterone: Normal male range.
- FSH/LH: LH elevated, FSH normal (androgen resistance).
- Uterus: Absent (Müllerian regression due to AMH).
- Breast development: Present (due to aromatization of testosterone).
- Pubic/axillary hair: Sparse/absent (androgen resistance).
- Malignancy risk: Moderate (5-10%) – requires gonadectomy after puberty.
- Genetics: AR mutation (X-linked).