Crouzon Syndrome: The Gentic Cause of the Skull Deformity
Crouzon syndrome is considered to be one of the commonest types of craniosynostosis - the premature fusion of skull bones. It is believed to be seen in 16 per million newborns. The growth of the skull is restricted as the flat plates of the skull fuse early. This distorts the shape of the skull and can lead to an unusual facial appearance. Almost all of the symptoms and features of this condition are derived from the early fusion of these bones. This can lead to a range of common problems including: -
- Bulging eyes
- High, prominent forehead
- Obstruction of the airways
- Beaked nose
- Underdeveloped upper jaw
- Optic nerve damage
- Increased pressure inside the skull
- Dental problems
- Hearing loss
In normal development the skull expands as the child’s brain grows. The expansion occurs at sutures - these are places where the bone plates meet. However, in Crouzon syndrome some of these plates have fused and so expansion cannot occur at the sutures. Therefore, compensatory expansion will occur at sutures that have not yet fued, and this can lead to abnormal shapes of the face and head.
Crouzon Syndrome Cause
The genetic causes of Crouzon syndrome are mutations in the FGFR2 gene. This gene codes for a protein called fibroblast growth factor receptor 2. Fibroblast growth factor receptors are involved in a number of processes including embryonic development, cell division, and regulation of cell growth and maturation. One of the functions of the FGFR2 protein is to signal immature cells to become bone cells during embryonic development.
It has been postulated that the genetic mutations lead to an overstimulation of the signalling of these proteins and this causes the bones to fuse prematurely.
Crouzon Syndrome Genetics
Crouzon syndrome follows an autosomal dominant pattern of inheritance. This means that a child will inherit the condition if it receives one abnormal gene from either of its parents.
If an affected parent has a child with an unaffected partner there is a 50% chance of the child inheriting the condition.
However, in about 50% of cases Crouzon syndrome occurs because of spontaneous genetic mutations. That is, neither parent has the condition.
Crouzon Syndrome Treatment
In common with many other genetic disorders there is no cure. However, many people with Crouzon syndrome will live a normal lifespan. Surgery is one treatment option which can stop the fusion of sutures from damaging the brain’s development. This can also help to reduce the pressure that can sometimes build up in the brain.
Other treatments include draining of excessive fluid round the brain, and supportive treatments for dental, eye, nose and throat problems. Speech therapy can also be used to help children with Crouzon syndrome to communicate.