RESUMO
46 XY pure gonad dysgenesia, also known as Swyer syndrome, is a disorder of sexual differentiation. The patients are phenotypic females with a 46 XY karyotype and hypoplastic gonads without germ cells. They present most often with primary amenorrhea. The study of this abnormality in testicular differentiation contributed to the identification of the gene SRY, testis determining factor. To date, 20% of 46 XY pure gonad dysgenesia are explained by a mutation or a deletion in SRY. In 80%, SRY is apparently normal. The risk of gonadal neoplasia is high, dictating early prophylactic removal of these dysgenetic gonads. Gonadoblastoma and dysgerminoma are the most frequently reported malignancies. Because of the possible inheritance of XY gonad dysgenesia all family members should undergo a thorough screening.