Neurofibromatosis Type 1 (NF or NF1) is an inherited condition that may cause changes in the skin, nervous system, bones, and endocrine glands. NF1 occurs in approximately 1 out of every 3,000 individuals. There are eight distinct types of NF, and NF1 comprises over 85% of all cases. Neurofibromatosis affects all races and is slightly more common in males. The skin shows evidence of café-au-lait spots and neurofibromas. Café-au-lait spots are light or dark-brown in color, flat and vary in size from small to very large (>20 cm). Café-au-lait spots may be present at birth or develop early in infancy or childhood. Small freckle-like spots are often seen in the underarm area or groin. Neurofibromas are usually smooth, soft, skin colored nodules that may occur anywhere on the skin and usually appear during puberty. Some skin findings may be present at birth. Some children with NF1 may have an increased head size.
Two of the following criteria for NF1 must be met:
Multiple (6 or more) café-au-lait spots >1.5 cm in size or >0.5 cm in size in children 5 years old or younger
Multiple freckles in the underarms and/or skin folds of the groin
Two or more neurofibromas, or a special type of neurofibroma found at birth or early infancy called a plexiform neurofibroma
A distinctive bone lesion, such as thinning of the outer shell of a long bone
Optic glioma (a benign tumor of the optic nerve)
Two or more Lisch nodules (dark spots on the iris of the eye)
First-degree relative with NF1
Symptoms and appearance
Café-au-lait spots are usually present during the first three years of life, while neurofibromas usually appear during adolescence and gradually increase in size and number. Freckles under the arms or in skin folds usually develop during the first 3-5 years of the child’s life. The course of NF varies considerably between patients depending on which organs are involved. Individuals with NF1 have a 50% chance of passing this condition on to their offspring.