A rare, genetic, peripheral neuropathy disorder due to gain-of-function mutations in voltage-gated sodium channels present in the small peripheral nerve fibers characterized by neuropathic pain of varying intensity (often beginning in the distal extermities and with a burning quality) associated with autonomic dysfunction (e.g. orthostatic dizziness, palpitations, dry eyes and mouth), abnormal quantitative sensory testing, and reduction in intraepidermal nerve ﬁber density. Large fiber functions (i.e. normal strength, tendon reflexes, and vibration sense) and nerve conduction studies are typically normal. The disease or phenotype is sodium channelopathy-related small fiber neuropathy (EFO_0700072).