Trisomy 18

background

In healthy individuals, cells contain 23 pairs of chromosomes (for a total of 46 chromosomes per cell). These chromosomes contain a person's genetic information. Each pair of chromosomes contains one chromosome from each parent. Trisomy 18, also called Edward's syndrome, is a genetic disease that is caused by the presence of an additional copy (or part of an additional copy) of chromosome 18.
When only some of a person's cells have the extra chromosome, it is called mosaic trisomy 18. In general, people who have only part of an extra copy of chromosome 18 and people with mosaic trisomy 18 have less severe symptoms than people who have an extra copy of the complete chromosome.
About one out of 3,000 conceptions are affected with trisomy 18. Additionally, about one out of 5,000-6,000 newborn babies have trisomy 18, suggesting that many embryos with trisomy 18 die before birth. About 80% of newborns affected with trisomy 18 are female.
Only 50% of newborns with trisomy 18 live past the first week of life, and only 5%-10% of newborns with trisomy 18 live past one year of age, due to a wide range of physical and mental developmental defects, including heart defects, kidney defects, mental retardation, and feeding problems. A small number of children may survive to their teenage years, but they will likely have serious medical problems. People who have only part of an extra copy of chromosome 18 and people with mosaic trisomy 18 are more likely to live longer than people who have an extra copy of the complete chromosome.

Related Terms

Chromosomal disorder, developmental defects, Edwards Syndrome, Edward's Syndrome, E3 Trisomy, genetic disorder, heart defects, kidney defects, nondisjunction, translocation.