Craniofacial anomalies – Crouzon syndrome
This syndrome is associated with craniosynostosis (premature closure of the bones in the skull). Approximately 5% of people with craniosynostosis will have Crouzon syndrome.
What causes Crouzon syndrome?
Two genes are known to be associated with Crouzon syndrome, FGFR2 and FGFR3. FGFR stands for fibroblast growth factor receptor. There are several fibroblast growth factor receptor genes, numbered 1 through 4. These genes are involved in the growth of the bones. The FGFR2 gene is the most common gene associated with Crouzon syndrome. Occasionally people with Crouzon syndrome also have a skin condition called acanthosis nigricans, and in these cases it is the FGFR3 gene responsible. Acanthosis nigricans is a condition in which there is increased thickness and increased pigmentation in some areas of the skin. The thickening and increased pigmentation can happen anywhere on the body but it more likely to occur in regions that move a lot.
Can Crouzon syndrome occur more than once in a family?
In about 25- 50% of people Crouzon syndrome is sporadic. This means there is no family history of the syndrome and it is unlikely to occur again in another pregnancy.
Crouzon syndrome is a variable condition. This means that a person who has this syndrome may not show all the symptoms. They may not even know they have it until they have a child who happens to have more of the features of Crouzon syndrome.
Crouzon syndrome is an autosomal dominant condition, so if a parent has Crouzon syndrome they have a 50 % (1 in 2) chance for each pregnancy of having a child with Crouzon syndrome.
What are some of the features?
Some people have craniosynostosis at birth. If they are going to develop craniosynostosis, it usually occurs in the first year of life and is very unlikely to occur after the age of 2 or 3 years. Common features are the shallow orbits and ocular proptosis, meaning the eyes are prominent. Conductive hearing loss (sound is not conducted from the external ear to the inner ear) is present in 55% of people with Crouzon syndrome. Both surgery and hearing aids can often help improve hearing. Those with Crouzon syndrome are at risk for headaches and seizures. The nose can be curved and the upper jaw may be small. Decreased jaw size can often lead to over-crowded teeth. Most people with Crouzon syndrome (97%) do not have mental retardation or learning problems.
Is there genetic testing?
Yes. There are gene tests available for both Crouzon Syndrome and Crouzon Syndrome with nigricans. Testing involves taking a blood sample. Testing can detect greater than 50% of the gene changes that cause Crouzon Syndrome alone and virtually all the gene changes that cause Crouzon syndrome with nigricans.
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- Jones K.L., Smith’s Recognizable Patterns of Human Malformation. 5th Edition. W.B. Soliders Company A Division of Harcourt Brace and Company, 1997.
- Online Mendelian Inheritance in Man, OMIM (TM). Johns Hopkins University, Baltimore, MD. MIM Number: 123500: 2000