We have studied a large Swedish family with a mutation in the nerve growth factor beta (NGFB) gene causing insensitivity to deep pain without anhidrosis (hereditary sensory and autonomic neuropathy, type V; HSAN V). Painfree joint destruction and fractures were common. Peripheral nerve conduction was normal, but temperature thresholds were increased. Sural nerve biopsies showed a moderate loss of A delta fibers and a severe reduction of C fibers. The three most severely affected cases were all born to consanguineous parents, and were homozygotes for the causal genetic mutation. Treatment of these patients is discussed.