Karyotype of Sweyer syndrome

Sweyer syndrome is an uncommon form of gonadal dysgenesis, characterized by a 46, XY karyotype. Despite the presence of a Y chromosome, the phenotype is female because the dysgenetic (streak) gonads produce neither AMH nor androgens. Consequently, the vagina, cervix, uterus, and fallopian tubes develop normally and the internal and external genitalia do not masculinize. In approximately 10-15% of patients, the disorder results from an inactivating mutation in the SRY gene, but in most, no cause can be identified. Patients with Swyer syndrome generally present after the expected time of pubey with delayed sexual maturation, primary amenorrhea, normal pubic hair, and normal female internal and external genital anatomy. Evaluation reveals hypergonadotropic hypogonadism, prompting a karyotype that establishes the diagnosis. Gonadectomy is indicated soon after diagnosis due to the significant risk for development of germ cell tumours in occult testicular elements (20-30%). Reference: Clinical Gynecologic Endocrinology; 8th edition; Chapter 9; Normal and Abnormal Sexual Development