Turner Syndrome and X Chromosome Defects
Since Turner syndrome and X chromosome defects are related, it's a good idea to have a basic understanding of the X chromosome problems that can cause the disorder. A woman with Turner syndrome will have one of three X chromosome defects, which include: defect of the X chromosome in all cells, absence of the X chromosome in some cells, and absence of the X chromosome in all cells.
The cause of Turner syndrome is a partial or complete absence of one of the two X chromosomes (sex chromosomes).
A woman with Turner syndrome will have one of three X chromosome problems:
- Defect of the X chromosome in all cells (see Turner syndrome and X chromosome defects)
- Absence of the X chromosome in some cells (see Mosaic Turner Syndrome)
- Absence of the X chromosome in all cells (see X Chromosome Monosomy).
A third cause of Turner syndrome involves X chromosome defects, rather than complete loss. For example, one X chromosome may be fragmented, have portions deleted, or have other structural problems, such as ring formation preventing the normal expression of X chromosome genes.
In a woman having one normal and one defective X chromosome, the symptoms vary widely.
A small deletion on the X chromosome may result in a single Turner syndrome feature, such as ovarian failure or short stature, and no other effects. Larger deletions or deletions on the X chromosome, affecting critical areas regulating the whole chromosome, may result in a full spectrum of Turner syndrome features.