Ullrich-Turner Syndrome (45,X-Syndrom) [Q96]
Dipl.-Biol. Uwe Heinrich
With an incidence of 1:2,500 in female newborns as well as an estimated number of 1:100 conceptions (approx. 98% of all pregnancies end in miscarriage during the 1st trimester), the Ullrich-Turner syndrome is one of the most frequent chromosomal abnormalities. Prenatal ultrasound examination can detect hygroma colli or hydrops fetalis at an early stage, which is in many cases an indication for invasive prenatal diagnosis and can bring evidence for the chromosomal abnormality. In severe cases, clinical signs and symptoms are short stature (approx. 150 cm), primary amenorrhoea, streak gonads, pterygium colli and mild facial signs of dysmorphia such as drooping eyelids. Intelligence is within the norm. Prenatally, a dilation of the lymphatic vessels with lymphedema and hygroma colli is frequently observed. Hormone replacement therapy should be administered for the development of secondary sexual characteristics. Although a deficiency in growth hormones is not present, in many patients an improvement in growth can be achieved by growth hormone substitution. If a 45,X/46,XY mosaic is present, the gonads should be removed prophylactically due to an increased risk for gonadoblastoma. Regarding differential diagnosis, the Noonan syndrome should be considered.
Approximately 55% of all patients exhibit a pure monosomy X, the rest exhibit gonosomal mosaicism or X chromosomal structural abnormalities.