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Neurofibromatosis is a genetic disorder that causes tumors to form on nerve tissue. These tumors can develop anywhere in your nervous system, including your brain, spinal cord and nerves. Neurofibromatosis is usually diagnosed in childhood or early adulthood.
The tumors are usually noncancerous (benign), but sometimes can become cancerous (malignant). Symptoms are often mild. However, complications of neurofibromatosis can include hearing loss, learning impairment, heart and blood vessel (cardiovascular) problems, loss of vision, and severe pain.
Neurofibromatosis treatment aims to maximize healthy growth and development and to manage complications as soon as they arise. When neurofibromatosis causes large tumors or tumors that press on a nerve, surgery can help ease symptoms. Some people may benefit from other therapies, such as stereotactic radiosurgery or medications to control pain.
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There are three types of neurofibromatosis, each with different signs and symptoms.
Neurofibromatosis 1 (NF1) usually appears in childhood. Signs are often evident at birth or shortly afterward, and almost always by age 10. Signs and symptoms are often mild to moderate, but can vary in severity.
Signs and symptoms include:
Flat, light brown spots on the skin (cafe au lait spots). These harmless spots are common in many people. Having more than six cafe au lait spots is a strong indication of NF1. They are usually present at birth or appear during the first years of life and then stabilize.
Freckling in the armpits or groin area. Freckling usually appears by ages 3 to 5. Freckles are smaller than cafe au lait spots and tend to occur in clusters in skin folds.
Tiny bumps on the iris of your eye (Lisch nodules). These harmless nodules can't easily be seen and don't affect your vision.
Soft bumps on or under the skin (neurofibromas). These benign tumors usually develop in or under the skin, but can also grow inside of the body. Sometimes, a growth will involve multiple nerves (plexiform neurofibroma).
Bone deformities. Abnormal bone growth and a deficiency in bone mineral density can cause bone deformities such as a curved spine (scoliosis) or bowed lower leg.
Tumor on the optic nerve (optic glioma). These tumors usually appear by age 3, rarely in late childhood and adolescence, and almost never in adults.
Learning disabilities. Impaired thinking skills are common in children with NF1, but are usually mild. Often there is a specific learning disability, such as problem with reading or mathematics. Attention-deficit/hyperactivity disorder (ADHD) is also common.
Larger than average head size. Children with NF1 tend to have a larger than average head size due to increased brain volume.
Short stature. Children with NF1 often are below average in height.
Neurofibromatosis 2 (NF2) is much less common than NF1. Signs and symptoms of NF2 usually result from the development of benign, slow-growing tumors (acoustic neuromas) in both ears. Also known as vestibular schwannomas, these tumors grow on the nerve that carries sound and balance information from the inner ear to the brain.
Signs and symptoms generally appear in the late teen and early adult years, and can vary in severity. Signs and symptoms can include:
Gradual hearing loss
Ringing in the ears
Sometimes NF2 can lead to the growth of schwannomas in other nerves of the body, including the cranial, spinal, visual (optic) and peripheral nerves. Signs and symptoms of these schwannomas can include:
Numbness and weakness in the arms or legs
Vision problems or the development of cataracts
This rare type of neurofibromatosis usually affects people after the age of 20. Schwannomatosis causes tumors to develop on skull (cranial), spinal and peripheral nerves — but not on the nerve that carries sound and balance information from the inner ear to the brain. Because tumors don't usually grow on both hearing nerves, schwannomatosis doesn't cause the hearing loss experienced by people with NF2.
Schwannomatosis causes chronic pain, which can occur anywhere in your body. Other symptoms include:
Numbness or weakness in various parts of your body
Loss of muscle
When to see a doctor
See your doctor if you or your child develops signs or symptoms of neurofibromatosis. The tumors associated with neurofibromatosis are often benign and slow growing. So although it's important to obtain a timely diagnosis, the situation isn't an emergency.
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Neurofibromatosis is caused by genetic defects (mutations) that either are passed on by a parent or occur spontaneously at conception. The specific genes involved depend on the type of neurofibromatosis:
NF1. The NF1 gene is located on chromosome 17. This gene normally produces a protein called neurofibromin that helps regulate cell growth. The mutated gene causes a loss of neurofibromin, which allows cells to grow uncontrolled.
NF2. The NF2 gene is located on chromosome 22, and produces a protein call merlin. The mutated gene causes a loss of merlin, leading to uncontrolled cell growth.
Schwannomatosis. So far, two genes are known to cause schwannomatosis.
The biggest risk factor for neurofibromatosis is a family history of the disorder. About half of people with NF1 and NF2 inherited the disease. NF1 and NF2 that isn't inherited results from new gene mutations.
NF1 and NF2 are both autosomal dominant disorders, which means that any child of a parent with the disorder has a 50 percent chance of inheriting the genetic mutation.
The inheritance pattern for schwannomatosis is less clear. Researchers currently estimate that the risk of inheriting schwannomatosis from an affected parent is about 15 percent.
Complications of neurofibromatosis vary, even within the same family. Generally, complications result from tumor growth distorting nerve tissue or pressing on internal organs.
Complications of NF1 include:
Neurological problems. Learning and thinking difficulties are the most common neurological problem associated with NF1. Uncommon complications include epilepsy and buildup of excess fluid in the brain.
Concerns with appearance. Visible signs of neurofibromatosis — such as extensive cafe au lait spots, numerous neurofibromas in the facial area or large neurofibromas — can cause anxiety and emotional distress, even if they're not medically serious.
Skeletal problems. Some children have abnormally formed bones, which can result in bowing of legs and fractures that sometimes don't heal. NF1 can cause curvature of the spine (scoliosis) that may need bracing or surgery. NF1 is also associated with decreased bone mineral density, which increases your risk of weak bones (osteoporosis).
Vision problems. Occasionally in children, an optic glioma can develop, affecting vision.
Problems during times of hormonal change. Hormonal changes associated with puberty, pregnancy or menopause might cause an increase in neurofibromas. Most women with NF1 have healthy pregnancies but will likely need monitoring by an obstetrician familiar with the disorder.
Cardiovascular problems. People with NF1 have an increased risk of high blood pressure and, rarely, blood vessel abnormalities.
Breathing problems. Rarely, plexiform neurofibromas can put pressure on your airway.
Cancer. An estimated 3 to 5 percent of people with NF1 develop cancerous tumors. These usually arise from neurofibromas under the skin or from plexiform neurofibromas. People with NF1 also have a higher risk of other forms of cancer, such as breast cancer, leukemia, brain tumors and some types of soft tissue cancer.
Benign adrenal gland tumor (pheochromocytoma). This noncancerous tumor secretes hormones that raise your blood pressure. A pheochromocytoma is generally surgically removed.
Complications of NF2 include:
Partial or total deafness
Facial nerve damage
Small benign skin tumors (skin schwannomas)
Weakness or numbness in the extremities
Multiple benign brain tumors or spinal tumors requiring frequent surgeries (meningiomas)
The pain caused by schwannomatosis can be debilitating and may require surgical treatment or management by a pain specialist.