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What are the genetics of neurofibromatosis?
There are two genetically distinct forms of neurofibromatosis.
The gene for NF-1 is more commonly affected and is located on chromosone 17. It is known as "peripheral neurofibromatosis."
The gene for NF-2 is less commonly affected and is located on chromosone 22. It is called "central neurofibromatosis" because it tends to affect parts of the body not readily seen by the outside observer.
The rest of this guide will refer specifically to neurofibromatosis type I.
How common is neurofibromatosis?
NF type I affects about 1 in every 3,000 newborn babies. There are many signs and symptoms. Doctors have come up with ways to rank their importance to be able to make more reliable diagnoses.
Patients may have "café-au-lait" spots which are darkened marks on the skin measuring about 5 mm in children and 15 mm on average in adults. Freckling in the armpit or groin area is also common. Other tumors may developl: optic glioma (a tumor of the main nerve to the eye), Lisch nodules (tumors of the iris which is the colored part of the eye), and bone lesions such as thinning or fracture of the tibia.
Other more rare signs include kyphoscoliosis (see Patient Guide to Scoliosis and Patient Guide to Kyphosis), differences in length between the two legs, elephantiasis, mental retardation, and high blood pressure.
The diagnosis may be more suspected in a person who has a family member affected by the disease.
What causes neurofibromatosis?
It is known that the disease is genetic, but how exactly this works is currently unknown.
What is the treatment?
There are indications for both medical and surgical care in neurofibromatosis.
Care should be coordinated by an expert in genetics (i.e. "medical geneticist") in cases involving peripheral and central lesions.
In cases where the tibia has not developed appropriately, bracing of the leg is commonly used. In cases when the tibia has actually fractured, surgery is necessary. The most common surgical procedure involves placing a rod down the middle of the tibia and then using bone graft (i.e. pieces of bone from another part of the patient's body or donated by another person to the bone bank) to close the fracture.
Electrical stimulation to the fracture area may sometimes help in the healing process. One final surgical possibility is taking part of the fibula and transferring it along with its blood supply to the affected limb.
In cases of scoliosis (see Patient Guide to Scoliosis) it may be necessary to brace the spine. This is done when the curve is over 25 degrees and does not have a sharp angle. More severe scoliosis may require the placement of metal rods along the back of the spine to straighten the curvature.
In cases where one leg grows longer than the other, a surgeon can fuse the growth plate so that the shorter leg has time to catch up. There are also techniques to lengthen the shorter leg.
What is the prognosis of neurofibromatosis?
Many serious medical conditions accompany this disorder as mentioned above. Life expectancy is shortened due to these factors. All individuals vary which makes prognosis different in each and every case. The orthopaedic manifestations can be supervised by the pediatric orthopaedic surgeon.
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