Descripción general
Schwannomatosis is a condition that results in slow-growing tumors on nerve tissue. The tumors can grow on nerves in the ears, brain, spine and eyes. They also can grow on peripheral nerves, which are nerves located outside of the brain and spinal cord. Schwannomatosis is rare. It's usually diagnosed in early adulthood.
There are three types of schwannomatosis. Each type is caused by an altered gene.
In NF2-related schwannomatosis (NF2), tumors grow in both ears and can cause hearing loss. The altered gene that causes this type is sometimes passed down from a parent. NF2-related schwannomatosis was previously known as neurofibromatosis 2 (NF2).
The other two types of schwannomatosis are SMARCB1-related schwannomatosis and LZTR1-related schwannomatosis. The altered genes that cause these types usually are not passed down through families.
The tumors caused by schwannomatosis usually are not cancerous. Symptoms can include headaches, hearing loss, trouble with balance and pain. Treatment focuses on managing symptoms.
Síntomas
Schwannomatosis symptoms depend on the type.
NF2-related schwannomatosis
Symptoms of NF2-related schwannomatosis (NF2) usually result from slow-growing tumors in both ears, known as acoustic neuromas or vestibular schwannomas. The tumors are benign, which means that they are not cancerous.
The tumors grow on the nerve that carries sound and balance information from the inner ear to the brain. These tumors can cause hearing loss.
Symptoms tend to appear during the late teen and early adult years, and can vary. Symptoms may include:
- Gradual hearing loss.
- Ringing in the ears.
- Poor balance.
- Headaches.
Sometimes NF2 can lead to the growth of tumors on other nerves, including in the brain, spine and eyes. They also can grow on peripheral nerves, which are located outside of the brain and spinal cord. People who have NF2 also may develop other benign tumors.
Symptoms of these tumors can include:
- Numbness and weakness in the arms or legs.
- Pain.
- Poor balance.
- Facial drop.
- Changes in vision or cataracts.
- Seizures.
- Headaches.
SMARCB1- and LZTR1-related schwannomatosis
These two types of schwannomatosis typically affect people after age 20. Symptoms usually appear between ages 25 and 30.
SMARCB1- and LZTR1-related schwannomatosis can cause tumors to grow on nerves in the brain, spine and eyes. Tumors also may grow on peripheral nerves located outside of the brain and spinal cord.
Symptoms of SMARCB1- and LZTR1-related schwannomatosis include:
- Long-lasting pain, which can occur anywhere in the body and can be disabling.
- Numbness or weakness in various parts of the body.
- Loss of muscle, known as atrophy.
These types of schwannomatosis also can cause tumors to grow in the ear. But it happens rarely, and tumors usually grow in only one ear. This differs from NF2, which causes tumors to grow in both ears. For this reason, people with SMARCB1- and LZTR1-related schwannomatosis don't have the same hearing loss as people who have NF2.
When to see a doctor
See a healthcare professional if you have symptoms of schwannomatosis. Although there is no cure, complications can be treated.
Causas
Schwannomatosis is caused by an altered gene. The specific genes involved depend on the type:
- NF2-related schwannomatosis (NF2). The NF2 gene produces a protein called merlin, also called schwannomin, that suppresses tumors. An altered gene causes a loss of merlin, leading to cell growth that's not controlled.
- SMARCB1- and LZTR1-related schwannomatosis. So far, two genes are known to cause these types of schwannomatosis. Changes of the genes SMARCB1 and LZTR1, which suppress tumors, are linked with these conditions.
Factores de riesgo
Patrón de la herencia autosómica dominante
Patrón de la herencia autosómica dominante
En un trastorno autosómico dominante, el gen alterado es un gen dominante. Está ubicado en uno de los autosomas, que son los cromosomas no sexuales. Solo se necesita un gen alterado para que una persona se vea afectada por este tipo de afección. Una persona con una afección autosómica dominante, en este caso, el padre, tiene un 50 % de probabilidades de tener un hijo con un gen alterado. Del mismo modo, tiene un 50 % de probabilidades de tener un hijo que no se vea afectado.
The gene that causes schwannomatosis is sometimes passed down from a parent. The risk of inheriting the gene differs based on the type of schwannomatosis.
For about half of people who have NF2-related schwannomatosis (NF2), they received an altered gene from a parent that caused the disease. NF2 has an autosomal dominant inheritance pattern. This means that any child of a parent who is affected by the disease has a 50% chance of having the gene change. People who have NF2 and whose relatives aren't affected are likely to have a new gene change.
In SMARCB1- and LZTR1-related schwannomatosis, the disease is less likely to be passed down from a parent. Researchers estimate that the risk of inheriting SMARCB1- and LZTR1-related schwannomatosis from an affected parent is about 15%.
Complicaciones
Complications can occur in schwannomatosis, and they depend on the type the person has.
NF2-related schwannomatosis complications
NF2-related schwannomatosis (NF2) complications can include:
- Partial or total hearing loss.
- Facial nerve damage.
- Vision changes.
- Small benign skin tumors, known as skin schwannomas.
- Weakness or numbness in the legs or arms.
- Having many benign brain tumors or spinal tumors, known as meningiomas. These require frequent surgeries.
SMARCB1- and LZTR1-related schwannomatosis complications
The pain caused by this type of schwannomatosis can be weakening. People with this type may need surgery or management by a pain specialist.