Skip to content

C18 Conditions

Learn about C18 abnormalities

Genetic Basis

Chromosome 18 conditions are caused by a change in a person’s genetic makeup.
Keep reading >


18p- happens when part of the short arm of one of the two copies of chromosome 18 is missing. This means there is one copy instead of two for each of the genes in the deleted region of the chromosome.
Keep reading >


18q- occurs when there’s a deletion of any size, and from any region, on the long arm of chromosome 18, also called the q arm.
Keep reading >

Tetrasomy p18

Tetrasomy 18p occurs when there is an extra chromosome that is made up of two copies of the short arm of chromosome 18 (the p arm). Instead of having two copies of the p arm of chromosome 18, people with Tetrasomy 18p have four copies.
Keep reading > 

Trisomy 18

Trisomy 18 is sometimes called “Edwards syndrome”. Trisomy 18 occurs when there are three copies of chromosome 18 in every cell of the body.
Keep reading > 

Ring 18

Ring 18 happens when one of the two copies of chromosome 18 forms a ring instead of the rod shape. When a ring forms, the tips of the chromosome are usually deleted.
Keep reading >

Pitt-Hopkins syndrome

PTHS is caused by a mutation within or a complete deletion of the TCF4 gene.
Keep reading > 

Stay in touch

Subscribe to our newsletter to get updates on events, announcements and fundraisers.