Turner syndrome (synonyms: 45,X/46,XX mosaic; 45,X/46,XY mosaic; gonadal dysgenesis; karyotype 45,X; karyotype 46,X iso (Xq); karyotype 46,X with gonosome abnormality, except iso (Xq); mosaic 45,,X/cell lines a. n.k. with gonosome anomaly; Turner anomaly of sex chromosomes; Turner syndrome; Ullrich-Turner syndrome; Ullrich-Turner syndrome (UTS); X0 syndrome; X monosomy; ICD-10 Q96.-: Turner syndrome) is a congenital disorder in which, due to a chromosomal aberration (abnormalities of the sex chromosomes), only one functional X chromosome is present in all or only part of all body cells instead of the two sex chromosomes XX. There is also the case that the second X chromosome is present but structurally altered.
Turner syndrome occurs only in girls or women. Due to the chromosomal abnormality, there is a deficiency of growth and sex hormones.
The clinical picture is associated with a wide variety of symptoms (see “Symptoms – Complaints”). The syndrome is fully expressed when one X chromosome is missing. Characteristic are short stature and absence of puberty.
The cause of the disease is spontaneous mutations. Turner syndrome cannot be inherited.
Frequency peak: It is estimated that about 3% of female embryos have functional Turner syndrome, but only 1-2% do not die during pregnancy.
The prevalence (disease incidence) is 0.0004% in live female births (in the world).
The incidence (frequency of new cases) is approximately 10 cases per 100,000 population per year among female live births (in the world).
Course and prognosis: The first characteristics of Turner syndrome can already be seen at birth. Thus, lymphedema (retention of lymphatic fluid in the tissues) as well as pterygium colli (wing-shaped lateral neck folds/wing skin) are observed. During puberty, there is absence of menstruation as well as underdevelopment of sex-specific characteristics. Also, body growth is greatly reduced. Turner syndrome has only a minor effect on cognitive ability. Significant developmental problems can be observed in only 10% of cases. In 2% of cases, a natural pregnancy may occur, but associated with a high rate of abortions (miscarriages).Therapy with growth and sex hormones allows affected individuals to lead an approximately normal life.
Mortality (number of deaths in a given period, relative to the number of the population concerned) is only slightly increased in relation to the normal population. With increasing age, the risk of dying from the congenital malformations (especially cardiac abnormalities) decreases steadily.
Comorbidities (concomitant diseases): Turner syndrome is increasingly associated with metabolic disorders, especially obesity.
Turner syndrome makes the risk of developing hemophilia (bleeding disorder) much higher because the usual second functional X chromosome is missing.
