title: Novel mutations in the CLCN1 gene of myotonia congenita: 2 case reports.
abstract: BACKGROUND
  Myotonia Congenita is an inherited myotonia that is due to a mutation in the skeletal muscle chloride channel CLCN1. These mutations lead to reduced sarcolemmal chloride conductance, causing delayed muscle relaxation that is evident as clinical and electrical myotonia.
  
  
  METHODS
  We report the clinical presentations of two individuals with Myotonia Congenita (MC).
  
  
  RESULTS
  Patient 1 has been diagnosed with the recessive form of MC, known as the Becker variant, and Patient 2 has been diagnosed with the dominant form of MC, known as the Thomsen variant. In both patients, the diagnosis was made based on the clinical presentation, EMG and CLCN1 gene sequencing. Patient 1 also had a muscle biopsy.
  
  
  CONCLUSIONS
  Genetic testing in both patients reveals previously unidentified mutations in the CLCN1 gene specific to Myotonia Congenita. We report the salient clinical features of each patient and discuss the effects and common types of CLCN1 mutations and review the literature.
authors.affiliation: University of Medicine and Health Services, New York, New York, USA.
authors.forename: Amanda Amrita
authors.initials: AA
authors.lastname: Lakraj
authors.forename: Geoffrey
authors.initials: G
authors.lastname: Miller
authors.forename: Alexander O
authors.initials: AO
authors.lastname: Vortmeyer
authors.forename: Babar
authors.initials: B
authors.lastname: Khokhar
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Nowak
authors.forename: Daniel B
authors.initials: DB
authors.lastname: DiCapua
mesh_terms: D001706:Biopsy; D002675:Child, Preschool; D018118:Chloride Channels / Q000235:genetics*; D004576:Electromyography; D006801:Humans; D008297:Male; D008875:Middle Aged; D009154:Mutation; D009224:Myotonia Congenita / Q000235:genetics* / Q000473:pathology / Q000503:physiopathology
chemical_list: C086321:CLC-1 channel; D018118:Chloride Channels
keywords: Becker variant; CLCN1 mutation; Myotonia Congenita; Thomsen variant