A 20-year-old woman presents with primary amenorrhea. She has normal female secondary sexual characteristics (breast development, female hair distribution) and height 165 cm. Examination reveals absent uterus and short, blind-ending vagina. Karyotype is 46,XY. The underlying diagnosis and the primary reason for normal breast development are:
- A Complete androgen insensitivity syndrome (CAIS); conversion of androgens to estrogen peripherally ✓
- B Müllerian agenesis (MRKH); normal ovarian estrogen
- C Swyer syndrome (46,XY pure gonadal dysgenesis); streak gonads producing estrogen
- D 5-alpha reductase deficiency; normal testicular estrogen secretion
Explanation
Complete Androgen Insensitivity Syndrome (CAIS) presents with 46,XY karyotype, absent Müllerian structures (AMH produced by testes prevents uterus/tubes), absent Wolffian structures (no androgenic response), normal female habitus, and absent pubic/axillary hair. Breast development occurs because testes produce testosterone, which is peripherally aromatised to estrogen — and without functional androgen receptors, estrogen effect predominates. MRKH has 46,XX karyotype. Swyer syndrome has streak gonads producing neither estrogen nor testosterone, so breasts do not develop without exogenous hormones.
Reference: Shaw's Textbook of Gynaecology, 17th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.