Neurofibromatosis (nu-ro-fi-bro-ma-tóe-sis), or NF, is a little-known genetic disorder that primarily affects the growth of neural (nerve) cells. NF is the most common neurological disorder caused by a single gene. This causes tumors to grow on nerves and produce other abnormalities such as skin changes and deformities. But NF may affect almost any organ of the body. It occurs equally in both men and women, in all races and ethnic groups. 50% of NF patients inherit the disease from a parent and 50% will result from a spontaneous genetic mutation with no family history of NF. Because the symptoms are varied, uncertain, and progressive, NF is hard to define or picture.