Neurofibromatosis type 1 (NF1) is a multisystem genetic disorder that commonly is associated with cutaneous, neurologic, and orthopedic manifestations. It is the most frequent of the so-called hamartoses, conditions characterized by non-neoplastic tissue overgrowth.
NF type 1 (NF1) is differentiated from central NF or NF type 2 in which patients demonstrate a relative paucity of cutaneous findings but have a high incidence of meningiomas and acoustic neuromas (which are frequently bilateral). NF1 has a lower incidence of central nervous system (CNS) tumors than NF2. However, complications of NF1 can include visual loss secondary to optic nerve gliomas, spinal cord tumors, scoliosis, vascular lesions, and long-bone abnormalities.
The manifestations of NF1 result from a mutation in or deletion of the NF1 gene. The gene product neurofibromin serves as a tumor suppressor; decreased production of this protein results in the myriad of clinical features.
The estimated incidence of NF1 is 1 in 3000, but the actual frequency may be higher because of less than complete ascertainment of mildly affected individuals. Approximately half of affected individuals represent first cases in the family as a result of a new genetic event or mutation.