Unexpected Virilization in a Patient with Turner Syndrome with Unbalanced Y/7 Translocation in the Gonadal Tissue: Gonadoblastoma Diagnosis.

Turner syndrome (TS) may involve tissue-restricted mosaicism, undetectable in standard peripheral blood karyotyping. This poses a diagnostic challenge, particularly when occult Y-chromosome material increases gonadoblastoma risk. We report an 18-year-old girl with TS (45,X), short stature on recombinant human growth hormone and severe intellectual disability, who developed virilization at age 12. Laboratory testing showed hypergonadotropic hypogonadism with elevated testosterone. Imaging failed to detect gonads. Bilateral gonadectomy revealed streak gonad tissue and testicular tissue with intratubular germ cell neoplasia and focal gonadoblastoma. High-resolution cytogenetics confirmed gonadal mosaicism with unbalanced Y/7 translocation, absent in lymphocytes. This case highlights that unexplained virilization in TS warrants immediate evaluation and that high-resolution genomic methods and timely gonadectomy are essential for cancer risk reduction.