A 16-year-old girl with primary amenorrhea has normal breast development (B4), absent pubic and axillary hair, and a blind-ending vagina. Karyotype reveals 46,XY. LH is elevated, testosterone is in the normal male range, and FSH is normal. This is:
- A Complete androgen insensitivity syndrome (CAIS) ✓
- B Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome
- C 5-alpha reductase deficiency
- D Swyer syndrome (46,XY complete gonadal dysgenesis)
Explanation
Complete androgen insensitivity syndrome (CAIS) presents as a phenotypically female 46,XY individual with normal breast development (from testosterone aromatized to estrogen), absent pubic/axillary hair (androgen action completely absent due to AR mutation), primary amenorrhea, and a blind-ending vagina (Müllerian regression from testicular AMH, no uterus). Testosterone is in the male range with elevated LH (lack of androgen feedback). Gonads are intra-abdominal testes requiring gonadectomy after puberty (malignant transformation risk). MRKH (46,XX) has normal pubic hair and normal gonadotropins. 5-alpha reductase deficiency (46,XY) presents with ambiguous genitalia at birth with virilization at puberty. Swyer syndrome has streak gonads and elevated FSH/LH with low estradiol.
Reference: Ghai Essential Pediatrics, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.