Neurofibromatosis-1 is an inherited disorder, characterized by formation of neurofibromas (tumors involving nerve tissue) in the skin, subcutaneous tissue, cranial nerves, and spinal root nerves.

NF1 is an autosomal dominant disease, meaning that if either parent has NF1, their children have a 50% chance of having the disease. NF1 also appears in families with no previous history of the condition, as a result of a new genetic mutation in the sperm or the egg. NF1 is caused by abnormalities in one of the genes encoding a protein called neurofibromin.

Neurofibromatosis causes unchecked growth of tissue along the nerves, which can put pressure on affected nerves and cause pain and severe nerve damage. This leads to loss of function in the area served by the nerve. Problems with sensation or movement can occur as a result, depending on the particular nerves affected.

Symptoms can be extremely varied, depending on the age of the patient and severity of the disease.

Symptoms may include:

• Mild impairment of intellectual function, attention deficit disorder
• Fracture of the long bones of the leg in early childhood
• "Coffee with milk" (cafe-au-lait) spots on the skin
• Freckles in the underarm or groin
• Convulsions
• Pain (associated with affected peripheral nerves)
• Blindness
• Rubbery tumors of the skin called nodular neurofibromas
• Soft tumors called plexiform neurofibromas which may have a darker color

The diagnosis of neurofibromatosis is generally made based on physical findings. The cafe-au-lait spot (meaning literally the color of coffee with milk) is the hallmark of neurofibromatosis. Although many healthy people have 1 or 2 small cafe-au-lait spots, adults with 6 or more spots greater than 1.5 cm in diameter are likely to have neurofibromatosis.

Other signs include:

• Freckling in the armpits, groin, or underneath the breast in women
• Multiple soft tumors apparent on the skin or deeper in the body viewed by various scanning methods
• Soft nodules under the skin
• Large infiltrating tumors under the skin (plexiform neurofibromas), which can cause disfigurement
• Pigmented, raised spots on the colored part (iris) of the eye (Lisch nodules)

• Examination by a doctor familiar with NF1, such as a neurologist, geneticist, or dermatologist
• Eye exam by an ophthalmologist familiar with NF1
• MRI of the affected site
• Removal of skin lesions
• Other specific tests associated with complications
• Genetic testing that demonstrates a mutation in the neurofibromin gene