Legius syndrome (https://omim.org/entry/611431) is an autosomal dominant disorder that shows some similarities to neurofibromatosis type I (NF1; 162200), which is caused by mutation in the neurofibromin gene (613113); however, Legius syndrome is less severe. Individuals with Legius syndrome typically have multiple cafe-au-lait spots, sometimes associated with skin fold freckling, variable dysmorphic features such as hypertelorism or macrocephaly, lipomas, and mild learning disabilities or attention problems. Legius syndrome is not associated with neurofibromas, optic gliomas, Lisch nodules, or tumor predisposition. The SPRED1 gene encodes a negative regulator of the RAS-MAPK pathway, similar to neurofibromin, and thus may be considered a RASopathy (review by Brems et al., 2012).