Crouzon syndrome

The FGFR2 gene provides instructions for making a protein called "fibroblast growth factor receptor 2." This is a protein (building block) that is important for many processes in the body such as cell division, cell growth, wound heading, creation of blood vessels, and the development of a baby. This protein is located on the outside of our cells and communicates with other chemicals and proteins outside of the cell. This protein plays an important role in bone growth especially in the early stages. If the FGFR2 gene has a harmful change (mutation) in it, cell communication and overall bone development is disrupted, leading to the features seen in Crouzon syndrome.

Not all mutations in the FGFR2 gene cause Crouzon syndrome. Mutations in the FGFR2 gene can also cause Apert syndrome, Beare-Stevenson cutis gyrata syndrome, Jackson-Weiss syndrome, lacrimo-auriculo-dento-digital syndrome, and Pfeiffer syndrome. Early fusion of the skull bones (craniosynostosis) is also seen in Apert syndrome, Beare-Stevenson cutis gyrata syndrome, Jackson-Weiss syndrome, and Pfeiffer syndrome.

Almost all people with a FGFR2 gene mutation associated with Crouzon syndrome are affected with the condition (complete penetrance). There has been only one family report in which two children and a father had a FGFR2 gene mutation associated with Crouzon syndrome, but two of these family members were mildly affected and one family member was not affected at all.

Only FGFR2 gene mutations are known to be associated with Crouzon syndrome. However, a specific mutation in the FGFR3 gene called p.Ala391Glu, p. A391G, or c.1172C>A causes Crouzon syndrome with acanthosis nigricans. Acanthosis nigricans is a skin condition where the folds and creases in the skin are dark colored (brown to black), thickened, and velvety.