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This is the more common of the two disorders. It is also called Von Recklinghausen's disease. The classic symptom of NF I is light brown patches of pigment on the skin, called café-au-lait spots. Benign (non-cancerous) skin tumors associated with this condition are called neurofibromas. Neurofibromas are often found growing on the nerves and in various organs of the person's body. There is a high rate of brain tumors in patients associated with NF.
Ten to 15 percent of individuals with NF will have malignant (cancerous) changes in the neurofibromas. Lisch nodules, which are small tumors on the iris (colored part of the eye), may appear around adolescence, but usually do not cause problems. Hearing loss, headaches, seizures, scoliosis, and facial pain or numbness may also be present. Mental retardation is present in 2 to 5 percent of individuals with neurofibromatosis I, while other persons affected may have learning problems and hyperactivity.