The past decade produced important advances in molecular genetic techniques potentially supplanting the traditional cytogenetic diagnosis of Turner syndrome (TS). Rapidly evolving genomic technology is used to screen 1st trimester pregnancies for sex chromosomal anomalies including TS, and genomic approaches are suggested for the postnatal diagnosis of TS. Understanding the interpretation and limitations of new molecular tests is essential for clinicians to provide effective counseling to parents or patients impacted by these tests. Recent studies have advanced the concept that X chromosome genomic imprinting influences expression of the Turner phenotype and contributes to gender differences in brain size and coronary disease. Progress in cardiovascular MRI over the past decade has dramatically changed our view of the scope and criticality of congenital heart disease in TS. Cardiac MRI is far more effective than transthoracic echocardiography in detecting aortic valve abnormalities, descending aortic aneurysm, and partial anomalous pulmonary venous return; recent technical advances allow adequate imaging in girls as young as seven without breath holding or sedation. Finally, important developments in the area of gynecological management of girls and young women with TS are reviewed, including prognostic factors that predict spontaneous puberty and potential fertility and recent practice guidelines aimed at reducing cardiovascular risk for oocyte donation pregnancies in TS. 1. Introduction Clinical consensus defines Turner syndrome (TS) as a genetic disorder due to “complete or partial” X chromosome monosomy, with short stature the most constant feature, and variable expressivity of ovarian, cardiovascular, and renal defects [1]. The phrase “complete or partial” is used to include several chromosomal etiologies leading to the syndrome. The most common is pure X monosomy (45,X—formerly designated 45X0). Some authors do not believe that complete X monosomy is compatible with survival and postulate the existence of a normal cell line that rescues the embryo during early gestation [2]. This view suggests that most if not all surviving apparently 45,X girls arose via loss of the 2nd sex chromosome during early mitotic cell divisions in preimplantation embryos [2]. This hypothetical scenario seems unlikely for several reasons. Firstly, available research on human gametes and embryos indicates that aneuploidy and chromosomal fragmentation commonly occur during meiosis, related to errors of homologous recombination [3, 4]. Moreover, if a sex chromosome is lost
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