Neurofibromatosis (NF) is a group hree conditions in which tumors grow in the nervous system. The three types are neurofibromatosis type I (NF1), neurofibromatosis type II (NF2), and schwannomatosis. In NF1 symptoms include light brown spots on the skin, freckles in the armpit and groin, small bumps within nerves, and scoliosis. In NF2, there may be hearing loss, cataracts at a young age, balance problems, flesh colored skin flaps, and muscle wasting. In schwannomatosis there may be pain either in one location or in wide areas of the body. The tumors in NF are generally non-cancerous.The cause is a genetic mutation in certain genes. These can be inherited from a person's parents, or in about half of cases spontaneously occur during early development. Different mutations result in the three types of NF. The tumors involve the supporting cells of the nervous system rather than the neurons. In NF1 the tumors are neurofibromas (tumors of the peripheral nerves), while in NF2 and schwannomatosis tumors of Schwann cells are more common. Diagnosis is typically based on symptoms, examination, medical imaging, and biopsy. Genetic testing may rarely be done to support the diagnosis.