Schwannomatosis

What causes schwannomatosis?

Some cases of schwannomatosis are caused by changes (mutations) in the SMARCB1 or LZTR1 genes. SMARCB1 and LZTR1 are tumor suppressor genes, which means that they encode a protein that stops cells from growing and dividing too rapidly or in an uncontrolled way. Mutations in these genes result in abnormal proteins that are unable to carry out their normal roles. This contributes to the development of the many different types of tumors found in schwannomatosis.

When schwannomatosis is caused by a mutation in SMARCB1 or LZTR1 , the affected person is typically born with one mutated copy of the gene in each cell and is, therefore, genetically predisposed to develop the tumors associated with the condition. For a tumor to form, two copies of the gene must be altered. The mutation in the second copy of the gene is considered a somatic mutation because it occurs during a person's lifetime and is not inherited.

In affected people without a mutation in SMARCB1 or LZTR1 , the underlying cause of the condition is unknown.

Last updated on 05-01-20

How is schwannomatosis diagnosed?

A diagnosis of schwannomatosis is often suspected based on the presence of characteristic signs and symptoms, especially if there are other family members with the condition. Additional testing can then be ordered to further support the diagnosis and rule out other conditions with similar features (namely, neurofibromatosis type 2). This may include:

  • Tumor pathology confirming that the growths are, in fact, schwannomas
  • Imaging studies, such as an MRI examining the vestibular nerve. It is important to rule out the presence of bilateral (affecting both sides) vestibular schwannomas which would be suggestive of neurofibromatosis type 2 rather than schwannomatosis
  • Genetic testing for a change (mutation) in the SMARCB1 or LZTR1 genes. Unfortunately, genetic testing is not informative in all people affected by schwannomatosis.

Last updated on 05-01-20

Is schwannomatosis inherited?

Approximately 15% percent of all schwannomatosis cases are thought to be inherited. In these cases, the condition is thought to be inherited in an autosomal dominant manner with highly variable expressivity and reduced penetrance. This means that a person only needs a change (mutation) in one copy of the responsible gene in each cell to have a genetic predisposition to the tumors associated with schwannomatosis. In some cases, an affected person inherits the mutation from an affected parent. Other cases may result from new (de novo) mutations in the gene. These cases occur in people with no history of the disorder in their family. People with an inherited form of schwannomatosis have a 50% chance with each pregnancy of passing the condition on to the next generation.

Last updated on 05-01-20

How might schwannomatosis be treated?

Treatment for schwannomatosis is based on the signs and symptoms present in each person. For example, pain is one of the most common symptoms of the condition. Treatment with medications such as gabapentin or pregabalin and the use of short-acting opioids and/or nonsteroidal anti- inflammatories for pain can be successful for many patients. If pain cannot be managed with other means or if the schwannomas are causing other symptoms, they can be surgically removed. However this treatment is often used as a last resort because surgery may put patients at risk of further neurologic problems.

Last updated on 05-01-20

Where To Start

Schwannomatosis - Children's Tumor Foundation

The Children's Tumor Foundation provides information about schwannomatosis. Click on the above link to access this information.

Last updated on 04-27-20

Name: Nerve Tumours UK 1st Floor 44 Coombe Lane
London, SW20 0LA, United Kingdom
Phone: 44(0)208 439 1234 Toll Free: 07939 046 030 (Helpline) Email: info@nervetumours.org.uk Url: https://nervetumours.org.uk
Name: Children's Tumor Foundation CTF 120 Wall Street, 16th floor
New York, NY, 10005-3904, United States
Phone: +1-212-344-6633 Toll Free: 1-800-323-7938 Fax : +1-212-747-0004 Email: info@ctf.org Url: https://www.ctf.org/
Yohay K & Bergner A.. Schwannomatosis UpToDate. 2015; Reference Link

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