[Turner syndrome].

Turner syndrome occurs in 1:5000 live births (1:2,500 females) and is caused not only by X-chromosome monosomy, but also in a large degree, by the presence of a mosaicism (45,X) and/or an abnormal X or Y chromosome (deletion, isochromosome X, dicentric chromosome). Clinical features are heterogeneous and typical physical anomalies are often mild or absent. In all cases, patients are short but final height has been improved by growth hormone therapy. Ovarian failure, with variable onset depending on the chromosomal anomalies, is frequent. Others visceral diseases (bone anomalies, lymphedema, deafness, and cardiovascular, thyroid, gastrointestinal diseases) are less common and need a screening at diagnosis, then a survey during adolescence and adulthood. During gestation, typical forms can be diagnosed by ultrasound examination, but mild forms are discovered incidentally during amniocentesis for unrelated reasons (advanced maternal age) and prenatal advice is difficult. The quality of life and social life is better when puberty is not induced too late, and in absence of cardiac disease or deafness. Deafness can lead to learning difficulties and, during adulthood, sterility can have a negative effect on quality of life. The prognosis depends on heart diseases, obesity, arterial hypertension and osteoporosis. Therefore, a long-term follow-up is necessary.