Neuropathy hereditary sensory and autonomic type 1
Overview
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).[3] Historical names include: Hereditary sensory radicular neuropathy, ulcero-mutilating neuropathy, thevenard syndrome, familial trophoneurosis, mal perforant du pied, and familial syringomyelia.[3] Sub-type 1C is also currently known as Charcot-Marie-Tooth type 2B syndrome (HMSN 2B).[3] 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. 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.
Prevention
Foot ulcers are frequently caused by breakdown of callus. Therefore, it is important to prevent callus formation by removing sources of pressure and to treat existing callus by softening the skin. Routine foot care by a diabetic clinic or by a podiatrist instructed to treat as for a diabetic foot is recommended. Burns can be prevented by using gloves as needed (e.g., during cooking). A diabetic education clinic is an excellent source of advice regarding skin care.
Diagnosis
The clinical diagnosis of HSN1 is based on the presence of prominent sensory loss with foot ulcers and shooting pains in one or more affected members of a family with what appears to be a CMT2 syndrome (i.e., axonal form of hereditary motor and sensory neuropathy). Sequence analysis of SPTLC1, the only gene known to be associated with HSN1, is available on a clinical basis.
Treatment
Wounds on neuropathic limbs heal if they are clean and protected and the limb is rested. Principles of treatment are the same as for leprosy surgery; see Warren & Nade (1999). Foot drop can be treated with ankle/foot orthotics (AFOs), but these need sleeving with stockings or some form of second skin to prevent skin abrasion. Charcot joints may require arthrodesis. Shooting pains are difficult to treat and only partial relief can be obtained with carbamazepine, gabapentin, or amitryptiline, or a combination of an antiepileptic and an antidepressant. Opiates are contraindicated as HSN1 is a chronic disorder.