Neurofibromatosis Type 1

Diagnosis

Doctors familiar with NF1 can usually make a diagnosis based on physical findings. They'll look for two or more of the following signs or symptoms (read more about symptoms):

• Six or more café au lait spots on the skin, larger than 5 millimeters (mm) across in children or 15 mm across in adolescents and adults
• Two or more neurofibromas or one plexiform neurofibroma
• Freckling under the arms or in the groin area
• An optic pathway glioma (a tumor — also called an optic nerve glioma)
• Two or more Lisch nodules
• Abnormal development of the temple bone (sphenoid dyplasia) or thinning of long bones (such as the tibia in the shin)
• A parent, sibling or child with NF1

Skin markings can be detected by visual examination. Lisch nodules are detected with a slit lamp, which uses a narrow beam of light and a microscope.

Other symptoms usually require more in-depth testing, including:

• Magnetic resonance imaging (MRI)
• X-rays
• Evaluation of skin lesions and possible removal
• Vision tests

To confirm a family history of NF1, parents, siblings or children may also need to be examined.

Genetic testing is also available for people without a family history or enough definitive symptoms to make a diagnosis. Testing cannot yet predict the symptoms or severity of symptoms that a person will experience.

Genetic testing is based on DNA analysis and has about a 95 percent chance of detecting a mutation in an individual with NF1. In addition to confirming the diagnosis, DNA results may help in prenatal diagnosis and detection of other family members at risk.