Neurofibromatosis 1 is a condition in which noncancerous tumors called neurofibromas grow along nerves in the skin, brain, and other parts of the body. Neurofibromatosis 1 is a subtype of neurofibromatosis. Beginning in early childhood, almost all people with neurofibromatosis 1 have multiple café-au-lait spots, which are flat, round spots on the skin that are the color of coffee with milk. These spots increase in size and number as the individual grows older. Freckles under the arms and in the groin develop later in childhood. Neurofibromatosis 1 is also characterized by the presence of neurofibromas, which are usually located on the skin and often increase in number over time. Neurofibromas may also occur in the spinal cord or along nerves elsewhere in the body. Cancers, which can include brain tumors and leukemia, occur in about 10 percent of individuals with neurofibromatosis 1. During childhood, benign (noncancerous) growths called Lisch nodules often appear in the iris (the colored part of the eye). Lisch nodules do not interfere with vision. Another type of tumor, called an optic glioma, can occur on the nerve leading from the eye to the brain and sometimes causes decreased vision or total vision loss. Additional signs and symptoms include high blood pressure and bony changes such as curvature of the spine (scoliosis). Most people with neurofibromatosis 1 have normal intelligence. Fewer than 10 percent are mentally retarded, but about half of affected children have learning disabilities.