- Down Syndrome/Trisomy 21 is caused by an extra chromosome 21 and includes a combination of birth defects. Affected individuals have some degree of intellectual disability, characteristic facial features, often heart defects, and other health problems. The severity varies greatly among affected individuals.
|1 in 691; 1 in 300 births at age 35
- Trisomy 13 is caused by an extra chromosome 13. Affected individuals have multiple birth defects and generally die in the first weeks or months of life.
|1 in 7,906
- Trisomy 18 is caused by an extra chromosome 18 and the affected individual also has multiple birth defects and early death.
|1 in 3,762
|Sex-Linked Chromosomal Disorders: The disorder occurs on chromosome pair #23 or the sex chromosomes.
|Cases per Birth
- Turner Syndrome is caused when all or part of one of the X chromosomes is lost before or soon after conception due to a random event. The resulting zygote has an XO composition. Turner Syndrome affects cognitive functioning and sexual maturation in girls. Infertility and a short stature may be noted.
|1 in 2500 females
- Klinefelter Syndrome is caused when an extra X chromosome is present in the cells of a male due to a random event. The Y chromosome stimulates the growth of male genitalia, but the additional X chromosome inhibits this development. The male can have some breast development, infertility, and low levels of testosterone.
|1 in 700 males