Muenke syndrome, which is named for Maximilian Muenke, the geneticist in whose lab the genetic disorder was first identified, is also known as FGFR3-related craniosynostosis. The condition occurs in approximately one in every 30,000 newborns and is characterized by deformities. It cannot be cured. Early surgery of the head and face is nearly always required to correct the deformities.
Definition & Facts
Muenke syndrome occurs as a result of early closure of the coronal suture of the skull. Sutures are the areas of separation between the skull bones, which are connected by thick fibrous tissue bands. As the child grows, the brain becomes larger, and sutures provide expansion room. The sutures gradually fill in and harden as the child grows, so the skull becomes solid, usually between the ages of 12 to 18 months.
The coronal suture separates the frontal bone over the top of the head and forehead from the parietal bones toward the back of the skull. In Muenke syndrome, the coronal suture closes much earlier than normal, which affects the shape of the head and face. In some cases, children with Muenke syndrome also have other abnormalities such as skeletal changes in the hands and feet, hearing loss, vision problems, or developmental delays.
Symptoms & Complaints
The upper jaw, cheekbones, and eyes sockets do not grow as much as the rest of the face. An underbite in which the lower teeth stick out further than the upper teeth is also typical. Children with Muenke syndrome often have broad toes.
Most also have a condition called brachydactyly, in which the fingers and toes are shorter than normal because the bones have not developed. Some children have a head that is larger than normal (macrocephaly). Hearing loss may be present in about one third of the cases.
Strabismus is the most common eye symptom and describes a condition in which the eyes are crossed. Children with Muenke syndrome usually have normal intellect, but developmental delays and learning disabilities can occur.
In some cases, people have the genetic mutations associated with Muenke syndrome but have no visible symptoms of the disorder. Symptoms can also vary considerably from one person to another.
Like other inherited head and facial development disorders, Muenke syndrome is caused by a genetic mutation. It stems from a mutation of the FGFR3 gene. The mutation causes the protein that FGFR3 gene makes to become overly active; it interferes with normal bone growth, which causes the skull bones to grow together much earlier than they normally would. Muenke syndrome is an autosomal dominant disorder. This means that the mutated gene can be inherited from only one parent.
Diagnosis & Tests
There are no specific laboratory tests for Muenke syndrome, although genetic testing can confirm the presence of the genetic mutation. The diagnosis is based on physical examination and imaging studies such as computed tomography (CT) scans or magnetic resonance imaging (MRI).
Doctors typically suspect Muenke syndrome when the suture on top of the an infant's skull is more narrow that would be expected for his or her age. The early closure may occur on one or both sides of the skull. In addition, the middle of the child’s face is underdeveloped. Symptoms can be mild or variable, so if a doctor suspects Muenke syndrome, he or she will usually recommend genetic testing.
Treatment & Therapy
Abnormal growth patterns may continue until the child reaches adulthood. Early and accurate diagnosis allows for early intervention, which can help prevent long-term disability.
Surgical correction of the skull is necessary to allow for proper brain development and is usually performed between the age of six and 12 months. In some cases, however, surgery may occur as early as three months. The surgeon(s) enter through an incision at the top of the head to remove the bone of the skull and reshape the facial bones.
A number of health professionals are involved in caring for a child with Muenke syndrome. The team may include both a craniofacial surgeon and neurosurgeon and a medical geneticist. In addition, children with Muenke syndrome may need care from an ophthalmologist, otolaryngologist, pediatrician, radiologist, psychologist, dentist, audiologist, speech therapist and/or social worker.
Prevention & Prophylaxis
In both cases, genetic testing can identify the presence of the defective FGFR3 gene. Once the presence of the gene has been confirmed, prospective parents can make an informed decision about their future.