What causes achondroplasia?

Genes are instructions for cells to make proteins in the body. Achondroplasia is the result of a pathogenic (disease-causing) change in the FGFR3 gene located on chromosome 4.

This gene provides instructions for a protein that is important for bone growth. When there is a pathogenic change in the FGFR3 gene, the protein is affected and bone development is impacted.

This causes affected individuals to be short, and have shortened upper limbs, hands and feet. Bones in the spine and legs are also at risk of curving.

How is achondroplasia inherited?

Everyone carries two copies of each gene, one inherited from each parent.

Achondroplasia follows a dominant inheritance pattern, which means that a pathogenic change in one copy of the FGFR3 gene can cause achondroplasia. If one parent has achondroplasia, a child has a 50% chance of inheriting the disease.

About 80% of people with achondroplasia have parents who are of average height, while the remaining 20% have at least one parent who has achondroplasia.