What is Trisomy 18?
Edwards’ Syndrome, also known as Trisomy 18, is a genetic condition that occurs when there is an extra copy of chromosome 18. Unlike normal chromosomes that have only two copies, one from each parent, the child has three copies of the chromosome. This genetic condition is mostly not hereditary, and it often randomly occurs before conception. The extra copies are found in either the egg or the sperm. It is a rare condition, but when it occurs it ranges from mild to severe life long effects.
It is important to note that the typical karyotype contains 23 pairs of chromosomes. A karyotype is the complete set of chromosomes for each individual. The typical number of chromosomes in a normal karyotype is 46. A person with a trisomy such as Edwards’ Syndrome has 47 chromosomes in their DNA. Trisomy can happen on other chromosomes, such as in cases of Down Syndrome or Patau Syndrome, but Edwards’ Syndrome specifically affects the 18th chromosome.
the different types
The severity of complications differs depending on the type of Trisomy 18. It’s important to recognize that there are three different variations of this disorder. They vary in terms of the affected cells and the degree of chromosomal replication that occurs.
The first variation, Full Trisomy 18, occurs when a person has three complete copies of their 18th chromosome in all of their cells. This can be visualized through an image displaying the affected cells prominently.
Partial Trisomy 18 is the second variation, where a third copy of the chromosome is partially replicated in every cell of the individual affected.
Mosaic Trisomy 18 is the third variation and affects only a portion of the individual’s cells. In this type, there are fewer than 85% of the person’s cells that show this chromosomal abnormality.
It’s important to note that prenatal screening and postnatal testing may detect Edwards Syndrome. Early detection allows parents to make informed medical decisions that can result in the best possible outcomes for their child
