Neurofibromatosis
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.
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