Neurofibromatosis is a genetically-transmitte disease in which nerve cells (Schwann cells) grow tumors (neurofibromas) that may be harmless or may cause serious damage by compressing nerves and other tissues. The tumors may cause bumps under the skin, colored spots, skeletal problems, pressure on spinal nerve roots, and other neurological problems. The disease occurs in approximately one in every 3,000 children.