Neurofibromatosis type 1 (NF1), also called von Recklinghausen's disease, is a rare genetic disorder characterized by the development of multiple noncancerous (benign) tumors of nerves and skin (neurofibromas) and areas of abnormally decreased or increased coloration (hypo- or hyperpigmentation) of the skin.
Areas of abnormal pigmentation typically include pale tan or light brown discolorations (cafe-au-lait spots) on the skin of the trunk and other regions as well as freckling, particularly under the arms (axillary) and in the groin (inguinal) area.
Such abnormalities of skin pigmentation are often evident by one year of age and tend to increase in size and number over time.
At birth or early childhood, affected individuals may have relatively large benign tumors that consist of bundles of nerves (plexiform neurofibromas).
Individuals with NF1 may also develop benign tumor-like nodules of the colored regions of the eyes (Lisch nodules) or tumors of the optic nerves (second cranial nerves), which transmit nerve impulses from the innermost, nerve-rich membrane of the eyes (retinas) to the brain.