Turner syndrome is one of the most common chromosomal disorders with a prevalence of 1:2,500 in female newborns and an estimated 1:100 conceptions (98% of these pregnancies end in miscarriage in the 1st trimester). Prenatal ultrasound may reveal early hygroma colli or hydrops fetalis which often leads to an invasive prenatal screening with detection of the chromosomal disorder. The clinical manifestations are short stature (approx. 150 cm), primary amenorrhea, stranded gonads, pterygium colli and slight facial dysmorphic signs such as outwardly tilted eyelid axes. Intelligence is within the normal range. Prenatally, dilatation of the lymphatic vessels with lymphedema and hygroma colli is common. In order to develop the secondary sexual features, a substitution with sex hormones is necessary. Although a growth hormone deficiency is not present, supplementation of growth hormones can improve growth in many patients. In cases of 45,X/46,XY mosaicism, sonographic monitoring of the gonads is recommended due to an increased risk of gonadoblastoma. Noonan syndrome should be considered as the primary differential diagnosis.
In about 55% of patients, a complete monosomy X is present, whereas in the remaining patients, gonosomal mosaics or X-linked structural anomalies are present.
Boucher et al. 2001, J Med Genet 38:591 / Ogata et al. 2001, J Med Genet 38:1 / Wieacker 2001, Medgen 13:3 / Tarani et al. 1998, Gynecol Endocrinol 12:83 / Swillen et al. 1993, Genet Counsel 4:7