Medical Definition of Neurofibromatosis type 1

Reviewed on 6/3/2021

Neurofibromatosis type 1: NF1, a genetic disorder characterized by a number of remarkable skin findings including multiple cafe au lait (coffee with milk) spots, multiple benign tumors called neurofibromas on the skin, plexiform neurofibromas (thick and misshapen nerves due to the abnormal growth of cells and tissues that cover the nerve), and freckles in the armpit and groin.

The cafe au lait spots increase in number and size with age. Ninety-seven percent of people with NF1 have 6 or more cafe au lait spots by age 20. The skin neurofibromas appear later, usually in the second decade of life. In NF1 there is an increased risk of scoliosis, optic gliomas (benign tumors on the optic nerve), epilepsy, and learning disability. The risk of malignant degeneration of neurofibromas is below 5 percent.

NF1 is inherited in an autosomal dominant manner and is due to mutation of the NF1 gene (in chromosome band 17q11) that encodes a protein called neurofibromin. Half of cases are due to new mutations in the NF1 gene. Prenatal testing is available. Also called von Recklinghausen disease.

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