A 19-year-old woman presents with primary amenorrhoea. She has normal breast development (Tanner stage 4) and absent pubic/axillary hair. External genitalia appear female with a blind-ending vaginal pouch. Serum testosterone is 6.8 nmol/L (normal male range 8–29 nmol/L). Karyotype is 46,XY. The MOST likely diagnosis is:
- A Complete androgen insensitivity syndrome (CAIS) ✓
- B 5-alpha reductase deficiency
- C Müllerian agenesis (MRKH syndrome)
- D Swyer syndrome (complete gonadal dysgenesis)
Explanation
Complete androgen insensitivity syndrome (CAIS) presents with: 46,XY karyotype, phenotypically female with female external genitalia and breast development (due to aromatisation of androgens to oestrogens), complete absence of pubic and axillary hair (due to androgen receptor insensitivity), blind-ending vagina (absent Müllerian structures due to AMH from testes), and normal-to-elevated male testosterone. MRKH has 46,XX. Swyer syndrome has streak gonads and no breast development without HRT. 5-alpha reductase deficiency presents with ambiguous genitalia and virilisation at puberty.
Reference: Shaw's Textbook of Gynaecology, 17th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.