Crouzon syndrome

What is it?

Crouzon syndrome is an inherited genetic disorder which causes craniosynostosis. In this condition the flat plates of bone that form the skull fuse together early in life, interfering with the growth of the skull, distorting the shape of the head and causing an unusual facial appearance.

It may be clear as soon as a baby with Crouzon syndrome is born that they have unusual features. As they grow, the shape of the head may distort further causing various problems.

Common problems in Crouzon syndrome include:

• Premature fusion of skull bones, including those around the eye and upper jaw
• High, prominent forehead
• Beak-shaped nose
• Abnormalities of the eyes, including hypertelorism (wide spacing), exophthalmos (protrusion), divergent strabismus (squint)
• Increased pressure inside the skull
• Hydrocephalus (too much cerebrospinal fluid in the brain cavities)
• Damage to the optic nerve
• Small upper jaw and short upper lip, with overcrowding of teeth
• Deafness due to blockage of the ear canal
• Obstruction of the airways
• Learning disabilities in about 12 per cent of cases
• Thickening of the skin and abnormal pigmentation in about 5 per cent of cases

What causes it?

It's caused by a problem with the gene for a chemical called fibroblast growth factor receptor 2 (FGFR2), which is involved in the formation of bones, skin and connective tissues. This is the same gene involved in Apert syndrome, but the mutation or change occurs in different parts of the gene.

The condition is inherited in an autosomal dominant way, so that each child of a person with Crouzon syndrome has a 50 per cent chance of inheriting the condition. However, in about half of all cases the syndrome has resulted from a new mutation (that is, neither parents were affected).

Like Apert syndrome, Crouzon syndrome may be more common among children born to older fathers.

What happens?

As a child's brain grows, normally the skull around it expands. This expansion occurs at joints called sutures, where the plates of skull bones meet. In Crouzon syndrome there's premature fusion of certain sutures. This begins in the first year of life and is complete by the second or third year.

The fused bones act as a single bony structure. Compensatory growth (in a different direction) occurs at those sutures that haven't yet fused, but this can change the shape of the face or head.

The rate and order in which different skull sutures fuse determines exactly how the skull becomes deformed and how severely the child is affected.

Typically, there's limited growth of the middle of the face, causing the eyes to protrude, and a short nose and small upper jaw (which can cause obstruction of the airways and difficulty breathing).

How's it treated?

Like other genetic conditions, Crouzon's cannot be 'cured'. But with the right help and care, most children lead a relatively normal life.

Surgery to unlock and move the bones of the skull, especially early in life, may be vital to prevent or treat increased pressure on the growing brain. It may also be used to reconstruct the appearance of the face and relieve protrusion of the eyes.

Excessive fluid around the brain (hydrocephalus) may need to be drained by inserting a tube called a shunt. Other specialist help, for example, to treat dental, eye or ear, nose and throat problems, is often needed.

Long-term supportive treatments such as speech therapy, psychological and educational help, and genetic counselling for the family are also important in helping the child to reach their potential.