A 19-year-old with primary amenorrhoea has breast development (Tanner stage IV), no pubic or axillary hair, and a blind-ending vaginal pouch of 4 cm depth. Karyotype is 46,XY. Testosterone level is 6.8 nmol/L (normal male range 8–30). FSH and LH are normal male range. What is the diagnosis and its critical medico-legal implication?

• A Swyer syndrome (46,XY gonadal dysgenesis); gonads should be removed early due to high gonadoblastoma risk
• B 5α-reductase deficiency; virilisation will occur at puberty, gonads should be preserved
• C Mayer-Rokitansky-Kuster-Hauser (MRKH) syndrome; vaginal reconstruction required
• D Complete androgen insensitivity syndrome (CAIS); gonads are typically retained until after puberty then removed due to 2–3% malignancy risk ✓

Explanation

Complete androgen insensitivity syndrome (CAIS) results from mutations in the androgen receptor (AR) gene on Xq11–12, causing complete resistance to androgens in a 46,XY individual. The testes produce testosterone and anti-Müllerian hormone (AMH) — testosterone cannot act (receptor defect), causing female external phenotype; AMH causes Müllerian regression, hence absent uterus and upper vagina. Testosterone level is in the low male range (binding available but non-functional). Breast development occurs from peripheral aromatisation of testosterone to oestrogen. Intra-abdominal testes carry a 2–3% lifetime malignancy risk (gonadoblastoma, seminoma) — current CAIS consensus is to delay gonadectomy until after puberty to allow oestrogen-driven growth, then remove. This case is legally sensitive as the individual has female gender identity.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.