A 22-year-old woman with primary amenorrhea has normal female external genitalia, absent uterus, blind vaginal pouch, and no axillary or pubic hair. FSH is 9 IU/L, LH 8 IU/L, testosterone 65 nmol/L (markedly elevated above female range). Her karyotype is 46,XY. This is BEST classified as:

• A 5-alpha reductase deficiency — autosomal recessive
• B Swyer syndrome (46,XY complete gonadal dysgenesis)
• C Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome type II
• D Complete Androgen Insensitivity Syndrome (CAIS) — type 1 with testicular feminization ✓

Explanation

Complete Androgen Insensitivity Syndrome (CAIS) is caused by mutations in the androgen receptor gene (AR, Xq11-12), resulting in complete end-organ resistance to androgens. The classic phenotype is: 46,XY karyotype, testes (intra-abdominal or inguinal), absent uterus and fallopian tubes (MIS/AMH from testes causes Müllerian regression), female external genitalia, absent pubic/axillary hair (as hair follicle androgenization is receptor-dependent), and markedly elevated testosterone (end-organ resistance). Swyer syndrome (46,XY gonadal dysgenesis) presents with streak gonads, low testosterone, and uterus present. MRKH is 46,XX with absent uterus but normal ovarian function. 5-alpha reductase deficiency presents with ambiguous genitalia at birth and virilization 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.