A 28-year-old woman presents with primary amenorrhea, phenotypically female, breast development present (Tanner stage IV), absent pubic and axillary hair, and absent uterus on ultrasound. Karyotype is 46XY. Serum testosterone is in the normal male range. This is most consistent with:

• A Complete androgen insensitivity syndrome (CAIS) — 46XY with androgen receptor gene mutation ✓
• B Mayer-Rokitansky-Küster-Hauser syndrome (MRKH) — Müllerian aplasia with 46XX karyotype
• C 5-alpha reductase deficiency — 46XY, male pseudohermaphroditism with virilization at puberty
• D Swyer syndrome (46XY pure gonadal dysgenesis) — no testosterone production, no secondary sexual development

Explanation

The triad of 46XY karyotype, female phenotype with breast development (estrogen effect from testicular aromatization), absent pubic/axillary hair (androgen insensitivity), absent uterus/vagina (AMH from testes suppresses Müllerian structures), and male-range testosterone = Complete Androgen Insensitivity Syndrome (CAIS), caused by loss-of-function mutations in the androgen receptor gene. MRKH is 46XX with no breast/hair issue. 5-ARD presents with virilization at puberty (not feminization). Swyer syndrome has no testosterone production and no breast development.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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