Freckling in the axillary area, groin, and other skin folds that are not exposed to the sun is common. Neurofibromas are another common feature. These benign tumors lie under the surface of the skin, and the number present is extremely variable. While some people only have a few tumors and others have hundreds or even thousands, most fall between the extremes. Scoliosis is also common in people with NF-1.
Tumors can form within the spinal column.
NF-1 affects roughly one person in 3000. Although roughly half of newly diagnosed cases are new mutations, any person who has NF-1 has a fifty percent chance of passing it on to their offspring. The gene for NF-1 is on chromosome 17. These can result in deafness, and symptoms usually appear in early adulthood. It affects roughly one person in 50,000.