NF1 and neurofibromatosis type 1: Germline loss-of-function mutations in the SPRED1 (Sprouty-related protein with an EVH1 domain-1) gene have been identified in patients meeting NIH clinical diagnostic criteria for neurofibromatosis type 1 (NF1) in whom NF1 mutations could not be identified; SPRED1 mutations represent at least 2% of pathogenic mutations in patients clinically diagnosed with NF1 (1, 2, 3).