In The US: About 1 in 3,000.
von Recklinghausen Disease
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The neurofibromatoses are a group of three genetically distinct disorders that cause tumors to grow in the nervous system. Tumors begin in the supporting cells that make up the nerve and the myelin sheath (the thin membrane that envelops and protects the nerves), rather than the cells that actually transmit information. The type of tumor that develops depends on the type of supporting cells involved.
Scientists have classified the disorders as neurofibromatosis type 1 (NF1, also called von Recklinghaus disease), neurofibromatosis type 2 (NF2), and a type that was once considered to be a variation of NF2 but is now called schwannomatosis. An estimated 100,000 Americans have a neurofibromatosis disorder, which occurs in both sexes and in all races and ethnic groups.
The most common nerve-associated tumors in NF1 are neurofibromas (tumors of the peripheral nerves), whereas schwannomas (tumors that begin in Schwann cells that help form the myelin sheath) are most common in NF2 and schwannomatosis. Most tumors are benign, although occasionally they may become cancerous.
Why these tumors occur still isn’t completely known, but it appears to be related mainly to mutations in genes that play key roles in suppressing cell growth in the nervous system. These mutations keep the genes—identified as NF1, NF2 and SMARCB1/INI1—from making normal proteins that control cell production. Without the normal function of these proteins, cells multiply out of control and form tumors.