Neurofibromatosis type 1: A model condition for the study of the molecular basis of variable expressivity in human disorders

Neurofibromatosis type 1 (NF1) is a pleiotropic autosomal dominant disorder with marked variability of clinical expression. As in other heritable disorders, the mapping and cloning of the gene responsible for NF1 have increased our understanding of the pathogenesis of the condition. In particular, the phenotypic variability and variable expressivity can be studied using molecular techniques. In this article we summarize the current knowledge of genotype/phenotype correlation in NF1 and examine the potential molecular basis for variable expressivity. Am. J. Med. Genet. (Semin. Med. Genet.) 89:7-13, 1999.