Crouzon syndrome is a form of craniosynostosis, which is characterized by skull and facial malformations. The condition occurs when the sutures between the bones of the skull close prematurely leading to distinctive facial abnormalities. The range and severity of abnormalities and symptoms can vary significantly from person to person.
Definition & Facts
Crouzon syndrome is named after French neurosurgeon Dr. O. Crouzon, who first described the condition in 1912. The disorder is rare in that it affects less than two out of every 100,000 people. Crouzon syndrome accounts for approximately four to five percent of all cases of craniosynostosis.
Individuals with the condition may also experience cervical spine deformities along with subtle anomalies of the elbows, musculoskeletal system, or internal organs. Crouzon syndrome differs from other forms of craniosynostosis in that it does not typically involve significant abnormalities of the hands and feet. Crouzon syndrome does not normally cause intellectual disability.
Symptoms & Complaints
Shallow eye sockets will make the eyes appear prominent and wide-set. It is also common for the eyes to have an outward gaze. Affected individuals may also have a small mid-face and beak-like nose. Other symptoms may include:
- Jaw and mouth anomalies—The upper jaw grows more slowly than the lower jaw, which will cause the lower jaw to protrude over time. The roof of the mouth may be tall and narrow, which can lead to crowded and misaligned teeth.
- Hearing loss—Approximately one-half of all patients with Crouzon syndrome have some degree of hearing loss and may require hearing aids.
- Joint problems—Approximately 30 percent of individuals with Crouzon syndrome have abnormalities involving the cervical spine.
- Skin abnormalities—People with Crouzon syndrome often have dark, thick, velvety skin around the mouth, neck, and eyelids. This condition is referred to as acanthosis nigricans.
- Breathing difficulties—A small nose and narrowed nasal cavity may lead to sleep apnea.
Infants may develop a bulging soft spot, become irritable or lethargic, or have a head that rapidly increases in size. Older children may complain of headaches, vision problems, or nausea and vomiting.
Crouzon syndrome is the result of a specific genetic mutation. The condition is considered autosomal dominant. This means that any child inheriting a copy of the gene from one parent has a 50 percent chance of being born with the condition.
The genetic mutation that causes Crouzon syndrome involves the fibroblast growth factor receptors, FGFR2 and FGFR3 located on chromosomes 4 and 10. These genes are responsible for producing a protein that signals cells in the developing embryo to become bone. It is believed that the mutated gene overstimulates the signaling of this protein, which leads to the early skull fusion.
There are instances of Crouzon syndrome in individuals with no family history of the condition. In these individuals, Crouzon syndrome may be the result of a random mutation occurring without a known cause.
Diagnosis & Tests
Since Crouzon syndrome frequently occurs in utero, the shape of a baby’s head is often the first indication that leads a doctor to suspect the child has the condition. A CT scan can help the doctor determine which sutures have fused and provide detailed information about the structures of the skull and brain.
X-rays may be used to identify potential abnormalities of the cervical spine. X-rays of the hand may also be used to differentiate whether the child has Crouzon syndrome or another form of craniosynostosis. The doctor may collect a small sample of cells from the neck to check for the presence of acanthosis nigricans. Genetic testing may also be recommended to determine if the child inherited the Crouzon genetic mutation from its parents or if the condition is the result of a mutation that is of unclear origin.
Treatment & Therapy
Surgery can be performed to reshape and expand the skull by removing the closed sutures. The surgery is typically performed during the first year of life, but the exact timing is determined by the number and type of closed sutures. Children with Crouzon syndrome are at risk for various visual impairments, so they should see an ophthalmologist on a regular basis to address potential problems.
Children with Crouzon syndrome should also be monitored for symptoms of hydrocephalus, which is a buildup of fluid in the brain. A cerebral shunt may be required to help the fluid drain from around the brain. Hearing aids and speech therapy may be useful in addressing hearing and speech difficulties resulting from abnormalities of the ear canal and palate.
Children with Crouzon syndrome should also see an orthodontist to address teeth crowding and misalignment caused by the palate's malformation. Dental extractions, dental braces, and jaw surgery may all be used to provide a more natural bite.
Babies having trouble breathing through their nose due to Crouzon syndrome may require a surgical tracheostomy to place a breathing tube in the windpipe. Older children with sleep apnea due to Crouzon syndrome may require a procedure designed to move the midface forward so that the upper and lower jaw align to create a larger airway.
Prevention & Prophylaxis
Approximately one-half of individuals with Crouzon syndrome without acanthosis nigricans has a detectable mutation of the FGFR2 gene. All patients who have Crouzon syndrome with acanthosis nigricans have a detectable mutation of the FGFR3 gene. It is important that anyone wishing to undergo genetic testing speak with a genetic counselor before testing to ensure they fully understand the risks and benefits of testing.