SMARCB1 Gene

Rhabdoid tumor predisposition syndrome (RTPS) is characterized by a high risk of developing cancerous (malignant) growths called rhabdoid tumors. These highly aggressive tumors are called rhabdoid because their cells resemble rhabdomyoblasts, which are cells that are normally found in embryos before birth and develop into muscles used for movement (skeletal muscles).

Rhabdoid tumors are rare in the general population. They usually occur in the first year of life, and are much less likely to appear after age 4. In people with RTPS, the tumors occur at an average age of 4 to 7 months, and can even occur before birth. Affected individuals may have multifocal synchronous tumors, which means that multiple tumors that develop independently (primary tumors) occur at the same time. The rhabdoid tumors that occur in RTPS usually grow and spread more quickly than those in children without this predisposition, and affected individuals often do not survive past childhood.

More than half of all malignant rhabdoid tumors (MRTs) develop in the cerebellum, which is the part of the brain that coordinates movement. Rhabdoid tumors in the brain and spinal cord (central nervous system) are called atypical teratoid/rhabdoid tumors (AT/RTs).

Rhabdoid tumors also occur outside the central nervous system. These tumors include rhabdoid tumors of the kidneys (RTKs) and tumors that develop in other organs and tissues of the body (called extrarenal malignant rhabdoid tumors or eMRTs). The type of rhabdoid tumor can vary among individuals with RTPS, even within the same family.

Tumors other than rhabdoid tumors can also occur in people with RTPS. Some affected children develop noncancerous (benign) tumors called schwannomas, which grow on nerve cells. Women with RTPS are at increased risk of developing a rare type of ovarian cancer called small cell cancer of the ovary hypercalcemic type (SCCOHT).

Schwannomatosis is a disorder characterized by multiple noncancerous (benign) tumors called schwannomas, which are a type of tumor that grows on nerves. Schwannomas develop when Schwann cells, which are specialized cells that normally form an insulating layer around the nerve, grow uncontrollably to form a tumor.

The signs and symptoms of schwannomatosis usually appear in early adulthood. The most common symptom is long-lasting (chronic) pain, which can affect any part of the body. In some cases, the pain is felt in areas where there are no known tumors. The pain associated with this condition ranges from mild to severe and can be difficult to manage. Other signs and symptoms that can occur with schwannomatosis depend on the location of the tumors and which nerves are affected. These problems include numbness, weakness, tingling, and headaches. The life expectancy of people with schwannomatosis is normal.

Schwannomatosis is usually considered to be a form of neurofibromatosis, which is a group of disorders characterized by the growth of tumors in the nervous system. The other two recognized forms of neurofibromatosis are neurofibromatosis type 1 and neurofibromatosis type 2. The features of schwannomatosis can be very similar to those of neurofibromatosis type 2. However, schwannomatosis almost never includes inner ear tumors called vestibular schwannomas, which are a hallmark of neurofibromatosis type 2. Additional features of the other forms of neurofibromatosis, including the development of other types of tumors, are much less common in schwannomatosis.