Neurofibromatosis (NF) is a condition that causes tumors to grow on nerve tissue, producing skin and bone abnormalities. NF is often diagnosed in childhood. The effects of the disease are varied – one child might live almost unaffected by the condition, whereas another might be severely disabled. Children with more severe forms of the disorder are usually diagnosed in infancy. Although there’s no specific cure for NF, tumors can usually be removed and related complications can be treated. Children with NF may need special schooling because learning disabilities are seen in about half of children with the disease.
What Is Neurofibromatosis?
Neurofibromatosis is a neurocutaneous syndrome (a genetic neurological disorder affecting the brain, spinal cord, nerves, and skin) in which tumors, called neurofibromas, grow along nerves in the body, or on or under the skin. The tumors arise from changes in the cells of the nerves and skin, and as they increase in size, they may press on vital areas of the body, causing problems in the way the body functions. It’s not uncommon for neurofibromas to first appear during childhood or sometimes during puberty. One of the first noticeable signs of the disorder is often cosmetic disfigurement caused by these tumors. Neurofibromas can often be removed. Although usually benign (noncancerous), they can sometimes become cancerous.
There are two types of neurofibromatosis, referred to as NF1 and NF2. NF1 is more common, occurring in one of every 4,000 births, and affecting an estimated 100,000 Americans. It is also known as von Recklinghausen disease.
The second type, NF2, is known as bilateral acoustic neurofibromatosis and is rarer, seen in one in 50,000 births. People with NF2 usually develop tumors on the nerves in their ears, causing hearing loss, eventual deafness, and problems with balance.
In both types of neurofibromatosis, the severity of the disorder varies greatly. In families where more than one person has NF, the disorder can progress with different physical signs and complications for each person. When NF is first diagnosed in a child, it isn’t possible to know right away if the child will have a mild form of the disease or will develop severe complications.
“The disorder can range from very mild to quite serious,” Dr. Allan E. Rubenstein, founder and medical director of the National Neurofibromatosis Foundation, says. “It is mild in most children.”
What Causes Neurofibromatosis?
Both types of neurofibromatosis are autosomal dominant genetic disorders, which means a child has a 50% chance of inheriting the disease if either parent has NF. Neurofibromatosis can also be the result of a spontaneous change (mutation) in the genetic material of the sperm or egg at conception in families with no previous history of the disease. About half of cases of neurofibromatosis are inherited, and the other half result from genetic mutation.
In the past 8 years, researchers have discovered two genes involved in causing neurofibromatosis. The NF1 gene is located on chromosome 17, and NF2 has been traced to chromosome 22. These findings are important because they may eventually lead to the development of a blood test or other genetic test to find out if a relative has NF.
Signs and Symptoms
NF1 is sometimes diagnosed in younger children, especially those with more severe forms of the disorder. One key to early diagnosis of mild NF is the appearance of café-au-lait spots (light brown patches that take their name from the French words for “coffee with cream”) on the child’s skin.
Many people who do not have NF have a few café-au-lait spots. But if a young child has five or more of these spots, at least 1/4 inch in size, a doctor will likely look for other clues that may indicate NF, including neurofibromas – tumors on, under, or hanging off the skin – and Lisch nodules, tiny, noncancerous tumors on the iris (the colored part of the eye). Lisch nodules are of no clinical significance except that they help confirm a diagnosis of NF. Neurofibromas often become evident on the skin around 10 years of age. A child may also develop freckling in the folds of the skin of the armpit or groin.
Abnormalities of the skeleton, such as the thinning or overgrowth of the bones in the arms or lower leg, curvature of the spine (scoliosis), and other bone deformities may also be features of NF1.
NF2 is usually not diagnosed until a child is older. Hearing loss in the late teens and early twenties is often among the first symptoms of the disorder, and is caused by tumors growing on the auditory nerves (the nerves that carry electrical impulses from the inner ear to the brain, allowing us to hear) on one or both sides. Other symptoms of NF2 might be continuous ringing in the ears, headache, facial pain or weakness, and feeling unsteady or off balance.
How Is It Diagnosed and Treated?
Neurofibromatosis is usually diagnosed based on a combination of findings. A child must have at least two of the following signs to be diagnosed with NF1:
- Café-au-lait spots of a certain number, size, and location
- The appearance of two or more neurofibromas (often resembling pea-sized bumps on the skin)
- Lisch nodules on the irises of the eyes
- An optic glioma (tumor along the main nerve of the eye that is responsible for sight)
- Certain skeletal abnormalities such as scoliosis (abnormal curvature of the spine)
- A family member with NF1
Tests like magnetic resonance imaging (MRI) and X-rays may be used to screen for tumors or evidence of skeletal problems. A child’s head circumference will be measured because children with symptoms of NF can have a larger than normal head circumference for a given age. Blood pressure will be monitored. Doctors will also take a detailed personal history, looking for signs of learning difficulties at home or at school.