Small-fiber neuropathy can be mixed, purely sensory, or purely autonomic, depending on the involvement of the nerve fibers (Johnson et al., 2021).In a study conducted on 921 patients with pure small-fiber neuropathy, 53% had idiopathic small-fiber neuropathy; in the remaining patients, immunological diseases (sarcoidosis, Sjogren, celiac, and autoimmune) were reported in 19%and sodium-channel-gene mutations (SCN9A, SCN10A, and SCN11A) in 16.7%. Here, SCN9A is linked to neuropathy, small fiber.