Crouzon syndrome is a genetic disorder. Its main feature is craniosynostosis, which is the abnormal growth and premature fusion of bones of the face and skull. The human skull is made up of over a dozen bones that grow together, and then slowly harden and fuse throughout early life, usually ending in your 20s. Crouzon syndrome occurs due to a mutation, most often in the FGF receptor-2 gene, which helps control bone and tissue growth in the skull. When this mutation occurs, bones grow too quickly and fuse too fast, often leading to a particular face shape – a flattened midface with either a sunken or beak nose, a long head, shallow eye sockets that make the eyes look very prominent, thin lips, and a large forehead. Crouzon syndrome can also cause increased intracranial (brain) pressure, which can have a variety of effects, ranging from mild to severe. Crouzon’s syndrome does not usually lead to intellectual disabilities, but in rare cases it can.
The symptoms of Crouzon syndrome are mostly caused by craniosynostosis. When the bones of the face and skull fuse too early, it can lead to symptoms that include:
Crouzon syndrome occurs due to mutations in the FGF2 gene. Normally, the FGF2 gene writes out the instructions required to make a protein called fibroblast growth factor receptor 2. One of the functions of that protein is to cause bone growth. People with Crouzon syndrome have a mutation in the FGF2 gene that makes that protein overactive, and the bones of their skull grow too fast and fuse too early.
The FGF2 mutation in Crouzon’s syndrome is an autosomal dominant mutation. This means that only one copy (not two) of the mutated gene is needed for Crouzon’s syndrome to show up. Sometimes this copy is inherited from parent to child. Other times, this mutation occurs sporadically, (due to a random, spontaneous mutation in the FGF2 gene, not inherited from parents).
Because Crouzon syndrome is a genetic disorder, the only risk factor that we’re sure of is known family history.
Diagnosing Crouzon’s syndrome requires combining a lot of information – symptoms, past medical history, imaging, and genetic testing. Usually, diagnosis starts with asking about your medical and family history, as well as doing a physical exam. This exam will have a special emphasis on the face and head, focusing on the features of Crouzon’s syndrome that are the most distinct. Then your doctor may want to do blood tests and imaging studies, such as MRIs and CT-scans of your brain. Finally, the most definitive diagnosis of Crouzon’s syndrome usually comes through genetic testing. Genetic testing is done easily and painlessly, usually by taking a sample of blood or saliva. Pieces of DNA in this sample can be used to diagnose Crouzon’s syndrome.
Most treatments for Crouzon syndrome centre around correcting facial abnormalities, and most of these corrections are done through surgery. Calvarial (calvaria means skull) vault remodelling for example, is a type of surgery that helps open up fused sutures. It’s usually performed in infancy (less than 1 year of age) so the babies still soft skull has time to remodel and shape correctly.
Other surgeries that treat Crouzon syndrome include the Lefort 3 procedure, which helps correct some of the midface abnormalities, and the monobloc procedure which helps correct some abnormalities of the eye socket.