Hereditary Sensory and Autonomic Neuropathy - Classification - Type 1

Type 1

Type 1 is the most common of the hereditary sensory and autonomic neuropathies (HSAN). Current names are: hereditary sensory neuropathy type I (HSN I), hereditary sensory and autonomic neuropathy type I (HSAN I). Historical names include: Hereditary sensory radicular neuropathy, ulcero-mutilating neuropathy, thevenard syndrome, familial trophoneurosis, mal perforant du pied, and familial syringomyelia. Sub-type 1C is also currently known as Charcot-Marie-Tooth type 2B syndrome (HMSN 2B).

Type 1 is transmitted as autosomal dominant trait and is characterized by a sensory deficit in the distal portion of the lower extremities, chronic perforating ulcerations of the feet and progressive destruction of underlying bones. Sweating abnormalities occur but other autonomic features are not found in this type. Symptoms appear in late childhood on early adolescence with trophic ulcers as pain sensation is affected more. Many patients have accompanying nerve deafness and atrophy of the peroneal muscles. Histopathologic examination reveals a marked reduction in the number of unmyelinated fibers. Motor nerve conduction velocities are normal, but the sensory nerve action potentials are absent.