title: [Distal hereditary motor neuropathy].
abstract: BACKGROUND
  Distal hereditary motor neuropathy (dHMN), also known as spinal muscular atrophy, represents a group of clinically and genetically heterogeneous diseases caused by degenerations of spinal motor neurons and leading to distal muscle weakness and wasting. Nerve conduction studies reveal a pure motor axonopathy and needle examination shows chronic denervation.
  
  
  BACKGROUND
  dHMN were initially subdivided into seven subtypes according to mode of inheritance, age at onset, and clinical evolution. Recent studies have shown that these subtypes are still heterogeneous at the molecular genetic level and novel clinical and genetic entities have been characterized. To date, mutations in 11 different genes have been identified for autosomal-dominant, autosomal-recessive, and X-linked recessive dHMN. Most of the genes encode protein involved in housekeeping functions, endosomal trafficking, axonal transport, translation synthesis, RNA processing, oxidative stress response and apoptosis.
  
  
  CONCLUSIONS
  The pathophysiological mechanisms underlying dHMN seem to be related to the "length-dependent" death of motor neurons of the anterior horn of the spinal cord, likely because their large axons have higher metabolic requirements for maintenance.
  
  
  CONCLUSIONS
  dHMN remain heterogeneous at the clinical and molecular genetic level. The molecular pathomechanisms explaining why mutations in these ubiquitously expressed housekeeping genes result in the selective involvement of spinal motor neurons remain to be unravelled.
authors.affiliation: Service de Neurologie Fonctionnelle et d'Épileptologie, Hôpital Neurologique Pierre-Wertheimer, 59, Boulevard Pinel, 69003 Lyon, France. perrine3112@yahoo.fr
authors.forename: P
authors.initials: P
authors.lastname: Devic
authors.forename: P
authors.initials: P
authors.lastname: Petiot
mesh_terms: D018450:Disease Progression; D005799:Genes, Dominant; D005808:Genes, Recessive; D018740:Genetic Heterogeneity; D015417:Hereditary Sensory and Motor Neuropathy / Q000145:classification / Q000175:diagnosis* / Q000235:genetics; D006801:Humans; D009134:Muscular Atrophy, Spinal / Q000175:diagnosis / Q000235:genetics; D010641:Phenotype