Neurofibromatosis type 1 (NF1) is a hereditary syndrome caused by mutations in a single gene, NF1. Kallionpää et al. used data from population-based cohort of Finnish patients with NF1 and nationwide health care registers, to study the association of NF1 and diabetes. They observed a reduced risk of diabetes, especially type 2 diabetes, among individuals with NF1. The hazard of type 2 diabetes was reduced by ~70% in NF1. This indicates that pathogenic variants of the NF1 gene may protect against diabetes, highlighting the Ras cell signaling pathway as a potential player in the pathogenesis of diabetes. (By Professor Juha Peltonen, https://jmg.bmj.com/content/early/2020/06/22/jmedgenet-2020-107062 )