Neurofibromatosis type I (NF-1) is a complex multi-system human disorder caused by the mutation of a gene on chromosome 17 that is responsible for production of a protein called neurofibromin which is needed for normal function in many human cell types. NF-1 causes tumors along the nervous system which can grow anywhere on the body. NF-1 is one of the most common genetic disorders and is not limited to any person's race or sex. NF-1 is an autosomal dominant disorder which means that mutation or deletion of one copy (or allele) of the NF-1 gene is sufficient for the development of NF-1, although presentation varies widely. As of 2015[update], there are at least 100,000 people in the U. S. and about 15,000 people in the UK who have been diagnosed with NF. Common symptoms of NF-1 include brownish-red spots in the colored part of the eye called Lisch nodules, benign skin tumors called neurofibromas, and larger benign tumors of nerves called plexiform neurofibromas, scoliosis (curvature of the spine), learning disabilities, vision disorders, mental disabilities, multiple café au lait spots and epilepsy. NF-1 affected individuals also have a much higher rate of cancer and cardiovascular disease than the population in general.