Prenatal Diagnosis of Turner Syndrome Mosaicism: A Case Report

Turner syndrome is a chromosomal disorder affecting females characterized by the partial or complete absence of one X chromosome. The pathogenesis of Turner syndrome primarily arises from chromosomal nondisjunction during gametogenesis, leading to various genotypic presentations. The most common genotype is 45, XO, representing a monosomy of the X chromosome. However, mosaicism, where different cell lines carry distinct chromosomal compositions, is also observed in some cases. This paper presents a case of prenatal diagnosis of Turner syndrome mosaicism with a genotype of 45, XO/46, XY. The patient, initially managed by her obstetrician/gynecologist, was referred to a perinatologist at 20 weeks and four days of gestation due to multicystic kidney findings in the fetus. Initial non-invasive prenatal testing (NIPT) suggested trisomy 22, but confirmation through amniocentesis revealed mosaic Turner syndrome (45, XO/46, XY). The pregnancy culminated in the delivery of a phenotypically female infant at 39 weeks gestation. Mosaic 45, XO/46, XY presents with a broad spectrum of phenotypic variability, ranging from classic Turner syndrome features to ovotesticular disorder and genital ambiguity, and even male genitalia with infertility. Patients with mosaic Turner syndrome require multidisciplinary follow-up due to the complexity of their condition. Additionally, the presence of Y chromosome material significantly elevates the risk of gonadoblastoma, necessitating consideration of prophylactic gonadectomy.