What is Turner Syndrome?
Turner syndrome (45,X) is a genetic disorder that occurs only in females and arises from partial or complete absence of the X chromosome. Turner syndrome occurs in 1 in 2,500 female births. H.H.Turner first described Turner syndrome in 1938 and the chromosomal basis of this syndrome was established in 1959 by Ford.
The physical phenotype of this syndrome includes:
- gonadal dysgenesis
- lack of pubertal maturation
- short stature
- shield chest
- webbing of the neck
- coarctation of the aorta
- horseshoe kidney
The neurocognitive profile of females with Turner syndrome includes:
- Preserved verbal skills
- Specific deficits in visuo-spatial tasks, visual memory, and arithmetic
- Verbal IQ is greater than Performance IQ
The psychosocial profile of females with Turner syndrome includes:
- Difficulty with school adjustment and facial affect recognition
- Social hypersensitivity
- Poor peer relations
What causes Turner Syndrome?
Turner syndrome is the only sex chromosome disorder in which complete absence of an X chromosome is compatible with life. The loss of one of the sex chromosomes in Turner syndrome probably occurs after the zygote has formed or just after the fusion of the gametes. It has been determined that approximately 50% of cases have a 45,X karyotype with the remainder having mosaic karyotypes. In addition, it has been found that in 70 to 80 % of the cases, the retained X is maternal in origin. Researchers have begun to speculate as to the possibility that genes are present on the X chromosome which are expressed differently depending on the parental origin of the X chromosome. The effects of genomic imprinting can be analyzed from the standpoint of physical and physiologic parameters in females with Turner syndrome.
Current TS Research at Stanford
Mosaic Karyotype in Turner Syndrome
- We are also conducting studies of brain development and cognitive functioning in girls with mosaic karyotype of Turner syndrome (45X/46XX and 45X/47XXX).
- We are examining the if mosaic karyotype modifies the neurocognitive and psychosocial profiles typically seen in females with Turner syndrome.
- The goal of this study is to increase our understanding of the relationship between genetics, brain development and behavior.