The symptoms of NF1 range from mild to severe, with some people experiencing more symptoms than others. Also, recognizable symptoms of NF1 typically develop before the age of 10 in most people, although some symptoms do not appear before the onset of puberty.

While NF1 has many manifestations, the appearance of multiple, flat, brown spots called café-au-lait spots is the most common sign. Café-au-lait spots are named from the French term “coffee with milk” because of their coloring, which is typically at least a shade darker than the general pigmentation of the skin. The spots commonly appear in the first few months of life and may continue to increase in number for several years. They are harmless and easily mistaken as birthmarks. Anyone can have one or two café-au-lait spots without having NF1; most people with NF have at least six and most have many more. The presence of this feature only suggests the possibility of NF1.

The disorder primarily affects the skin, nervous system, and the eyes, although bones and the vascular system can also be affected. The most common symptoms of NF1 include:

• Six or more café-au-lait spots on the skin
• Freckles under the arms and in the groin region
• Tan bumps on the iris (called Lisch nodules)
• Neurofibromas, soft benign tumors that develop under the skin