The presence of multiple café-au-lait spots strongly suggests, but doesn't prove, the diagnosis of NF1. In rare cases, there may be individuals who have as many as six café-au-lait spots but do not seem to have other features of NF1.

The presence of café-au-lait spots is one criterion for the diagnosis, but at least two features of the disorder need to be present to confirm the condition. Through an extensive physical examination and in some rare cases tests such as biopsies, X-rays, or additional medical tests, a doctor will look for two or more of the following features:

Diagnostic Criteria for Neurofibromatosis 1

1. Six or more café-au-lait spots measuring at least 5 mm in size before puberty and 15 mm in size after puberty
2. Two or more neurofibromas or one plexiform neurofibroma
3. Freckles in the axilla (under the arms) or groins
4. Lisch nodules on the iris of the eye
5. Optic glioma
6. Specific skeletal abnormalities such as tibial dysplasia (bowing of shin bone) and abnormality of the orbit
7. NF1 by above criteria in a parent, sibling, or offspring.