NGF and hereditary sensory and autonomic neuropathy type 5: The genetic analyses of northern Swedish individuals with a rare pain-free congenital disorder called hereditary sensory and autonomic neuropathy type V (HSAN V)6 revealed a mutation in the ngf gene in which arginine 100 was replaced by tryptophan (R100W), attracting attention as a disease that encompasses the specific role of NGF in pain.