NF disease, or neurofibromatosis, is a group of genetic conditions that cause tumors to grow along nerves throughout the body. These tumors are usually noncancerous but can lead to a wide range of complications depending on where they develop. There are three distinct types, each caused by different gene mutations: neurofibromatosis type 1 (NF1), neurofibromatosis type 2 (NF2), and schwannomatosis.
The Three Types of Neurofibromatosis
NF1 is by far the most common form, affecting roughly 1 in 3,000 people. It causes soft, fleshy tumors called neurofibromas to grow on or under the skin, along with distinctive skin markings like light brown patches (called café-au-lait spots) and freckling in areas like the armpits and groin. NF1 can also affect bones, eyes, and the brain.
NF2 is much rarer and looks quite different. Its hallmark is tumors called vestibular schwannomas that grow on the nerves responsible for hearing and balance, almost always on both sides. Despite some name overlap, NF2 does not cause the skin neurofibromas seen in NF1.
Schwannomatosis is the rarest form. It produces multiple tumors called schwannomas on peripheral and spinal nerves, often causing chronic pain. Unlike NF2, it rarely involves the hearing and balance nerves.
How NF1 Affects the Body
NF1 is present from birth, but many of its features develop gradually during childhood and continue to change throughout life. The earliest signs are usually café-au-lait spots: flat, light brown patches on the skin. Six or more spots larger than 5 mm in a child (or 15 mm after puberty) are a key diagnostic marker. Freckling in the armpits or groin, which typically appears by age 3 to 5, is another early sign.
Neurofibromas, the condition’s signature tumors, tend to increase in number during puberty and pregnancy. Most are small, painless bumps on or just beneath the skin. A more concerning type, called plexiform neurofibromas, can grow along larger nerves and become quite large. These deeper tumors can press on surrounding tissues, cause pain, and in a small percentage of cases, transform into cancerous tumors.
NF1 can also affect the skeleton, causing curved bones (particularly the shinbone), scoliosis, and in some cases bones that fail to heal properly after a fracture. Some children develop a tumor on the optic nerve called an optic pathway glioma, which can affect vision. Small, harmless spots on the iris of the eye, visible only with a special lamp, are another common finding.
Learning and attention difficulties are among the most common challenges children with NF1 face, even when the condition is otherwise mild. High blood pressure is another known complication, which is why blood pressure checks are part of routine monitoring.
How NF2 Affects the Body
NF2 typically becomes apparent in the late teens or twenties. Almost all affected individuals develop tumors on both hearing and balance nerves by age 30. The first symptoms are often subtle: ringing in one ear, difficulty hearing on the phone, or feeling unsteady when walking in the dark or on uneven ground. Hearing loss can come on gradually or, less commonly, happen suddenly if the tumor compresses a blood vessel supplying the nerve.
Balance problems in NF2 deserve special attention. People with vestibular tumors can become dangerously disoriented underwater, which creates a real drowning risk during swimming. NF2 can also cause tumors on the membranes surrounding the brain and spinal cord.
Genetics and Inheritance
All three types of neurofibromatosis follow an autosomal dominant inheritance pattern, meaning a single copy of the altered gene is enough to cause the condition. If one parent has NF, each child has a 50% chance of inheriting it. NF1 is caused by a mutation in the NF1 gene on chromosome 17, which normally produces a protein that helps regulate cell growth. When that protein doesn’t work correctly, cells can grow more freely, leading to tumor formation.
About half of all NF1 cases are inherited from a parent, and the other half arise from a new, spontaneous gene mutation in someone with no family history. This means NF can appear for the first time in any family.
How NF Is Diagnosed
NF1 is diagnosed clinically, meaning doctors look for a combination of physical features rather than relying on a single test. Under the international consensus criteria, a person without an affected parent needs at least two of the following signs:
- Café-au-lait spots: six or more, with the size threshold adjusted for age
- Freckling in the armpits or groin
- Neurofibromas: two or more of any type, or one plexiform neurofibroma
- Optic pathway glioma
- Iris spots (Lisch nodules) or specific eye findings seen on imaging
- Bone abnormalities such as a curved shinbone or skull bone changes
- Genetic testing confirming a mutation in the NF1 gene
If a parent already has a confirmed NF1 diagnosis, only one of these features is needed to diagnose a child. At least one of the skin-related signs (café-au-lait spots or freckling) should appear on both sides of the body.
Treatment Options
There is no cure for neurofibromatosis, but treatments can manage specific symptoms and complications. For most people with mild NF1, the condition requires monitoring rather than active treatment. Neurofibromas that cause pain or cosmetic concerns can be surgically removed, though new ones may develop over time.
For children and adults with NF1 who have symptomatic plexiform neurofibromas that can’t be safely removed with surgery, the FDA has approved a medication (sold as Koselugo) that can shrink these tumors. It works by blocking a signaling pathway that drives tumor growth and is approved for patients one year of age and older. This was a significant development because plexiform neurofibromas were previously untreatable when surgery wasn’t an option.
NF2 management focuses on preserving hearing and neurological function for as long as possible. Treatment decisions around vestibular schwannomas involve balancing tumor growth against the risks of surgery or radiation to the hearing nerve.
Ongoing Monitoring
Children with NF1 need regular, structured follow-up. Recommended surveillance includes annual eye exams through adolescence, yearly physical exams to check for new or changing tumors, annual skeletal assessments for scoliosis and bone problems until growth is complete, blood pressure checks every year, and neurological evaluations for headaches, seizures, or pain. Brain MRI is not done routinely but is ordered when symptoms suggest a problem.
People with more complex disease, such as large or growing plexiform neurofibromas, intracranial tumors, or vascular issues, need more frequent and targeted follow-up.
Life Expectancy and Long-Term Outlook
NF1 varies enormously from person to person. Some people have only mild skin findings and live essentially normal lives. Others develop serious complications. A large study using U.S. death certificates found that the average age at death for people with NF1 was about 15 years lower than the general population. Even among those who survived past 40, life expectancy was still reduced by roughly 9 years. The leading causes of early death are malignant tumors that develop from neurofibromas and other NF1-related cancers.
These are population averages, and they include the full spectrum of severity. Many people with NF1 live into their 60s, 70s, and beyond, particularly with regular monitoring that catches complications early.