nF-1 or classic neurofibromatosis, is characterised by the familiar cafe- au-lait spots, axillary freckling, cutaneous and visceral neurofibromas (which sometimes undergo malignant transformation), gliomas, scoliosis, and Lisch nodules of the iris. NF-1 is associated with the the von recklinghausen Neurofibromatosis locus that encodes the NF-1 protein, a gTPase activating protein which interacts with the ras proteins. The gene is located on chromosome 17.
nF-2, also called acoustic or central neurofibromatosis, features neurofibromas restricted to the acoustic nerve (usually bilateral) and the central nervous system, skin lesions may or may not be present. The gene is located on chromosome 22.
There are no biochemical markers of the disorder, but the cloning of both the nF-1 and NF-2 genes makes dNA-based diagnosis possible in some families. Both genes appear to be tumour suppressor genes. Both conditions are autosomal dominant, but the variable penetrance and expressivity and [[high frequency of new mutations make genetic counseling difficult.