A FAMILY WITH AUTOSOMAL DOMINANT MUTILATING NEUROPATHY NOT LINKED TO EITHER 3q13‐q22 OR 9q22 LOCI

Abstract

The clinical separation of CMT2 from HSAN I may be difficult in some kindreds in which the sensory and motor symptoms and deficits are approximately alike. The genetic studies of CMT2 families are also controversial: one form of CMT2 was shown to map on chromosome 3q13‐q22 and named CMT2B; the HSAN I locus was mapped to 9q22.1. We describe a family with an autosomal dominant inheritance in which at least three members, belonging to three generations, developed a progressive neuropathy that combined limb weakness, wasting, and severe distal sensory loss leading to prominent mutilating changes. The onset was in late childhood, with progressive weakness in the lower limbs and later in the hands, resulting in a severe paralysis in the feet in one patient. Sensory disturbances were pronounced in 2 patients, and led to poorly healing ulcerations with osteomyelitis and amputations in one foot and mutilating lesions of both hands. Electrophysiological investigation revealed an axonopaty with consistent motor damage. Sural nerve biopsy showed a reduction in the density of both myelinated and unmyelinated fibers, with regenerating clusters.Linkage analysis using 5 microsatellite markers within to the critical 9q22 region was performed. Lod scores of this family calculated by LINKAGE package excluded association to this locus. We also performed linkage studies with chr. 3q13‐q22 markers associated to the CMT2b locus. Lod scores excluded this locus as well as responsiblity of the familial phenotype. The severity of motor involvement would suggest classifying the disorder of this family as a form of HSMN II rather than HSAN, indicating that a new locus is involved in the pathogenesis of this disorder.