A 22-year-old woman presents with primary amenorrhoea. She has normal secondary sexual characteristics, 46,XY karyotype, and bilateral testes in the inguinal canals. Serum testosterone is in the male range. The most likely diagnosis is:

• A Swyer syndrome (pure gonadal dysgenesis 46,XY)
• B Complete androgen insensitivity syndrome (CAIS) ✓
• C 5-alpha reductase deficiency
• D Kallmann syndrome

Explanation

CAIS is caused by mutations in the androgen receptor gene (AR), rendering all androgen-responsive tissues insensitive to testosterone. Affected individuals have 46,XY karyotype with testes (often inguinal/labial), develop female external genitalia and normal breast development (aromatisation of testosterone to oestrogen), absent pubic/axillary hair (androgen-mediated), primary amenorrhoea (no uterus), and male-range testosterone. Swyer syndrome has streak gonads and female phenotype with no secondary sexual development. 5-alpha reductase deficiency causes ambiguous genitalia.

Reference: Shaw's Textbook of Gynaecology, 17th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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