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Neurofibromatosis (NF) is a genetic neurological disorder that causes tumors to form on the nerve tissue.
Neurofibromatosis (NF) is a genetic neurological disorder that causes tumors to form on the nerve tissue. These tumors, also known as neurofibromas, can develop in any part of the nervous system—the brain, spinal cord, and nerves supplying body parts. Typically, the tumors are noncancerous and grow on the nerves and on or underneath the skin. NF often causes bone deformities besides skin changes. Symptoms are usually present at birth or develop during childhood and may worsen as a patient grows older. Some people have mild symptoms that are not noticeable, whereas, in others, NF causes significant disability.
The life expectancy of a person with NF is approximately 8 years less than that of the general population. Lifetime risks of both benign and malignant tumors are increased in individuals with neurofibromatosis type 1 (NF1). If there are no complications, the life expectancy of people with NF is almost normal in most cases.
Types of neurofibromatosis
There are three types of neurofibromatosis (NF) each with distinct signs and symptoms:
- Neurofibromatosis type 1 (NF1)
- Neurofibromatosis type 2 (NF2)
- Schwannomatosis (SWN)
Neurofibromatosis type 1 (NF1)
Neurofibromatosis type 1 (NF1), also known as von Recklinghausen disease, is the more common type, mostly affecting the nerves of the peripheral nervous system. Usually, symptoms begin to appear at birth or early in life and include:
- Multiple birthmarks: Multiple coffee-colored birthmarks of various shapes measuring about 5-15 mm appear on the body before a child is 2 years of age.
- Axillary and inguinal freckling: Freckles appear in the armpit and groin areas.
- Multiple neurofibromas: Small, painless, and slow-growing tumors form nodules on the skin that may appear at any age but often appear around adolescence.
- Plexiform neurofibromas: Sometimes, a tumor involves multiple nerves and grows to a very large size and is called a plexiform neurofibroma. It causes pain, weakness in the arms or legs, and problems with appearance or can be life-threatening.
- Lisch nodules: These are small brown tumors that often appear on the iris. They do not affect vision and can be seen with a special lamp called a slit lamp.
- Learning disabilities: These appear in many children with NF1 causing difficulties in reading, mathematics, or spelling.
- Macrocephaly (an oversized head): Children with NF1 have a larger head size due to an increased brain volume.
- Short stature: Children who have NF1 are often below average in height.
- Orthopedic problems: Common orthopedic problems in children with NF1 include:
- Scoliosis: Noticeable sideways curve of the spine looking like the letter “S” or “C”
- Kyphosis: A spinal curve that results in an abnormally rounded back
- Congenital pseudarthrosis of the tibia: Bowing of the tibia occurs before a child is 2 years old
- Bone deformities: Abnormal development of the eye socket
- Cancer risk: Most NF1 tumors are benign; however, there is a slightly increased risk (10%) that a neurofibroma can become cancerous.
- Other complications: Signs of mental retardation, speech problems, and hypertension may be seen in some children with NF1.
Neurofibromatosis type 2 (NF2)
Neurofibromatosis type 2 (NF2), also known as bilateral acoustic neurofibromatosis (NF), is less common than neurofibromatosis type 1 (NF1) and is usually diagnosed in early adulthood. NF2 mostly causes tumors in the central nervous system and vestibulocochlear nerves that control hearing and balance.
People with NF2 may develop:
- Schwannomas: These are tumors of the Schwann cell (which produce a sheath that covers and protects the peripheral nerves).
- Auditory neuroma: Most people with NF2 develop tumors on the nerve that
- processes hearing. As the tumors grow bigger, it leads to progressive hearing loss.
- Meningioma: It is a tumor that arises in the tissue covering the brain and spinal cord.
- Ependymoma: It is a tumor that arises within the spinal cord.
- Visual problems: Cataracts or changes appear at an early age.
- Peripheral neuropathy: Individuals with NF2 may develop problems with nerve function leading to numbness and weakness in the arms and legs with or without muscle loss.
- Other complications:
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Schwannomatosis
Schwannomatosis (SWN) is the rarest form of neurofibromatosis (NF), and it causes intense pain. It is genetically and clinically distinct from neurofibromatosis type 1 (NF1) and neurofibromatosis type 2 (NF2). SWN causes multiple tumors or schwannomas to develop on the cranial, spinal, and peripheral nerves—but not on the auditory (vestibulocochlear) nerve. SWN is usually diagnosed in early adulthood. It usually affects people after the age of 20 years, and symptoms appear between the ages of 25 and 30 years.
People with SWN may have
- Chronic pain anywhere on the body due to enlarging tumors.
- Numbness and tingling of the arms or legs.
- Weakness in the fingers and toes.
- Loss of muscle.
What causes neurofibromatosis?
Neurofibromatosis (NF) occurs as a result of defects in different genes. Nearly half of the cases of NF are inherited, whereas the other half is caused by a spontaneous mutation of the gene.
- Neurofibromatosis type 1 (NF1) is caused by mutation of or faulty neurofibromin gene located on the pericentromeric region of chromosome number 17.
- Neurofibromatosis type 2 (NF2) is caused by mutation of or faulty gene on chromosome 22.
- Schwannomatosis (SWN) is caused by mutation of or faulty SMARCB or LZTR1 genes.