Neurofibromatosis: Causes, Symptoms, and Diagnosis

Neurofibromatosis is a medical condition that is not isolated. This term describes three distinct disorders characterized by the growth of tumors that can impact the brain, spinal cord, and nerves that transmit information from the brain to the spinal cord to every place in the body. While some tumors may develop into malignant (cancerous), most are benign (non-cancerous). 

What is Neurofibromatosis?

Neurofibromatosis is a condition in which tumors develop on nerve tissue that is caused by a class of hereditary illnesses. The brain, spinal cord, and nerves are among the parts of the nervous system where these tumors can form. Neurofibromatosis type 1 (NF1), Neurofibromatosis type 2 (NF2), and schwannomatosis are the three forms of the disease. Children are typically diagnosed with NF1, but early adulthood is typically when NF2 and schwannomatosis are identified.

Usually benign (noncancerous), the tumors associated with these illnesses might occasionally develop into malignant (cancerous). Most symptoms are not severe. Neurofibromatosis can cause hearing loss, learning disabilities, heart and blood vessel issues, blindness, and excruciating pain, among other difficulties.

Types

Neurofibromatosis can be characterized into three types:

• Neurofibromatosis Type1 (NF1): Of the three disorders, neurofibromatosis 1 (NF1) is the most prevalent. 30% to 50% of instances of NF1 are caused by a spontaneous genetic mutation in the NF1 gene, even though many NF1 patients inherit the gene that causes the disorder. The faulty gene can be inherited after this mutation has taken place. There is a 50% probability that a child of an afflicted parent will inherit the gene mutation. With NF1, children and adults may experience various symptoms and health issues that vary with age. The majority of NF1 patients enjoy an average lifespan. Because numerous NF1 clinical characteristics evolve at various stages, correctly diagnosing might take years.
• Neurofibromatosis Type2 (NF2): Compared to NF1, neurofibromatosis 2 (NF2) is less frequent. In around half of the cases, the NF2 gene is inherited (familial); in the other half, a spontaneous genetic mutation causes the disorder. A parent with the faulty NF2 gene has a 50% probability of passing it on to each of their offspring.
• Schwannomatosis (SWN): The least frequent form, schwannomatosis (SWN), has several subtypes based on the particular genetic mutation causing it (e.g., SMARC-B, LZTR, XXX). There are instances where there are no symptoms. Others experience chronic discomfort, tingling in the fingers and toes, and slow-growing nerve tumors called schwannomas that are occasionally limited to a single body area.

Causes

Genetic flaws (mutations) that may arise spontaneously during conception or be passed on from one’s parents cause neurofibromatosis. Different genes are involved depending on the kind of neurofibromatosis.

• NF1: Chromosome 17 is home to the NF1 gene. This gene produces the neurofibromin protein, which aids in controlling cell proliferation. The mutant gene’s lack of neurofibromin permits unchecked cell growth.
• NF2: The NF2 gene, which is found on chromosome 22, generates the tumour-suppressive protein Merlin. The mutant gene’s lack of Merlin results in uncontrolled cell development.
• Schwannomatosis: Schwannomatosis is currently associated with two genes. Mutations affecting the tumour-suppressive genes SMARCB1 and LZTR1 are linked to this kind of neurofibromatosis.

Symptoms

Neurofibromatosis type 1 (NF1): Symptoms of NF1 consists of:

• Family history of NF1.
• The presence of pea-sized bumps (neurofibromas) on or just under the skin.
• Six or more café-au-lait spots on the skin.
• Larger patches on or under the skin that appear bloated (plexiform neurofibromas).
• Pigmented lumps on the iris of the eye are called Lisch nodules.
• Freckling beneath the arms or in the groin area.
• A tumor on the optic nerve may impair eyesight.
• Skeletal abnormalities, such as scoliosis, weakening of the shin bone, and bowing of the legs (tibial dysplasia).

Neurofibromatosis type 2 (NF2): Symptoms of NF2 consists of:

• Schwannomas, or tumors along the eighth cranial nerve.
• Hearing loss, deafness, or ringing sounds inside the ears (tinnitus).
• Brain cancers, including meningiomas.
• Balance issues.
• Early-stage cataracts.
• Tumors of the spine.
• Muscular atrophy, or muscular loss. 

Schwannomatosis: Most cases of this uncommon form of neurofibromatosis occur in adults over 20. It usually takes between 25 and 30 years to show symptoms. Tumors caused by schwannomatosis typically arise on the cranial, spinal, and peripheral nerves, but not on the nerve responsible for transmitting balance and sound information from the inner ear to the brain. People with schwannomatosis do not typically experience the same degree of hearing loss as those with NF2, as tumors do not form on both hearing nerves. However, these are a few symptoms to look out for:

• Severe chronic pain, which can happen anywhere in the body
• Loss of muscular mass
• Numbness or weakness in several body areas

Diagnosis

Clinical characteristics alone may make it impossible to differentiate between an individual with NF2 and someone with SWN. For those with characteristics of these disorders without a known family history or bilateral vestibular schwannomas (those that affect both sides of the body), genetic testing might be necessary to make the proper diagnosis.

Based on symptoms, subsequent imaging and detailed MRI imaging of the brain and spinal cord are required, which may reveal schwannomas on peripheral nerves.

Neurofibromatosis is a genetic disorder that affects the nervous system, disrupting the growth and development of nerve cells. It causes tumors to form on nerves, which are typically benign but can sometimes become cancerous. This condition arises from either a genetic mutation or inheritance. Once acquired, it can be passed down to children.

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