Complete androgen insensitivity syndrome in a 15-year-old female with primary amenorrhea and undescended testes: a rare case report

Morris syndrome, also known as Complete Androgen Insensitivity Syndrome (CAIS), is a rare genetic disorder of sex development characterized by a 46, XY karyotype with female external genitalia due to androgen receptor mutations. We present a case of a 15-year-old phenotypically female patient who presented with primary amenorrhea despite normal secondary sexual characteristics. Physical examination revealed a BMI of 14.81 kg/m², developing breasts and sparse pubic hair consistent with Tanner stage 3, normal external female genitalia, and a blind-ended vaginal canal. Imaging studies demonstrated absence of uterus and ovaries, with 2 solid oval-shaped hypoechoic structures in the right inguinal region consistent with undescended testes, while the left inguinal region remained empty. Hormonal analysis revealed markedly elevated testosterone levels (643.6 ng/dL) within the male reference range and decreased estradiol levels (25.45 pg/mL). Cytogenetic analysis confirmed a 46, XY karyotype in all cells examined. This case highlights the importance of considering androgen insensitivity syndrome in phenotypically female patients presenting with primary amenorrhea, elevated testosterone levels, and absent uterine structures. Early diagnosis is crucial for appropriate management, including psychological support, hormone replacement therapy planning, and timely gonadectomy due to increased malignancy risk in undescended testes.