title: An atypical case of SCN9A mutation presenting with global motor delay and a severe pain disorder.
abstract: BACKGROUND
  Erythromelalgia due to heterozygous gain-of-function SCN9A mutations usually presents as a pure sensory-autonomic disorder characterized by recurrent episodes of burning pain and redness of the extremities.
  
  
  METHODS
  We describe a patient with an unusual phenotypic presentation of gross motor delay, childhood-onset erythromelalgia, extreme visceral pain episodes, hypesthesia, and self-mutilation. The investigation of the patient's motor delay included various biochemical analyses, a comparative genomic hybridization array (CGH), electromyogram (EMG), and muscle biopsy. Once erythromelalgia was suspected clinically, the SCN9A gene was sequenced.
  
  
  RESULTS
  The EMG, CGH, and biochemical tests were negative. The biopsy showed an axonal neuropathy and neurogenic atrophy. Sequencing of SCN9A revealed a heterozygous missense mutation in exon 7; p.I234T.
  
  
  CONCLUSIONS
  This is a case of global motor delay and erythromelalgia associated with SCN9A. The motor delay may be attributed to the extreme pain episodes or to a developmental perturbation of proprioceptive inputs.
authors.affiliation: Pediatrics Department, Pediatric Neurology Division, CHU Sainte Justine, Montréal, Quebec, Canada.
authors.forename: Inge Anita
authors.initials: IA
authors.lastname: Meijer
authors.forename: Michel
authors.initials: M
authors.lastname: Vanasse
authors.forename: Sonia
authors.initials: S
authors.lastname: Nizard
authors.forename: Yves
authors.initials: Y
authors.lastname: Robitaille
authors.forename: Elsa
authors.initials: E
authors.lastname: Rossignol
mesh_terms: D002220:Carbamazepine / Q000627:therapeutic use; D002675:Child, Preschool; D015897:Comorbidity; D004916:Erythromelalgia / Q000188:drug therapy / Q000453:epidemiology / Q000235:genetics; D005260:Female; D006801:Humans; D006987:Hypesthesia / Q000188:drug therapy / Q000453:epidemiology / Q000235:genetics; D008801:Mexiletine / Q000627:therapeutic use; D019957:Motor Skills Disorders / Q000188:drug therapy / Q000453:epidemiology / Q000235:genetics*; D020125:Mutation, Missense / Q000235:genetics*; D062556:NAV1.7 Voltage-Gated Sodium Channel / Q000235:genetics*; D012720:Severity of Illness Index; D013001:Somatoform Disorders / Q000188:drug therapy / Q000453:epidemiology / Q000235:genetics*; D016896:Treatment Outcome
chemical_list: D062556:NAV1.7 Voltage-Gated Sodium Channel; C486866:SCN9A protein, human; D008801:Mexiletine; D002220:Carbamazepine
keywords: Nav1.7; SCN9A; axonal neuropathy; developmental delay; erythromelalgia; pain