title: Muscle phenotype in patients with myotonic dystrophy type 1.
abstract: BACKGROUND
  The pathogenesis of muscle involvement in patients with myotonic dystrophy type 1 (DM1) is not well understood. In this study, we characterized the muscle phenotype in patients with confirmed DM1.
  
  
  METHODS
  In 38 patients, muscle strength was tested by hand-held dynamometry. Myotonia was evaluated by a handgrip test and by analyzing the decrement of the compound muscle action potential. Muscle biopsies were assessed for morphological changes and Na(+)-K(+) pump content.
  
  
  RESULTS
  Muscle strength correlated with a decline in Na(+)-K(+) pump content (r = 0.60, P < 0.001) and with CTG expansion. CTG expansion did not correlate with severity of myotonia, proximal histopathological changes, or Na(+)-K(+) pump content. Histopathologically, we found few centrally placed nuclei (range 0.2-6.9%).
  
  
  CONCLUSIONS
  The main findings of this study are that muscle weakness correlated inversely with CTG expansion and that central nuclei are not a prominent feature of proximal muscles in DM1.
authors.affiliation: Neuromuscular Research Unit, Department of Neurology, 3342, Rigshospitalet Blegdamsvej 9, DK-2100, Copenhagen, Denmark. grete.andersen@rh.dk
authors.forename: Grete
authors.initials: G
authors.lastname: Andersen
authors.forename: Mette C
authors.initials: MC
authors.lastname: Ørngreen
authors.forename: Nicolai
authors.initials: N
authors.lastname: Preisler
authors.forename: Eskild
authors.initials: E
authors.lastname: Colding-Jørgensen
authors.forename: Torben
authors.initials: T
authors.lastname: Clausen
authors.forename: Morten
authors.initials: M
authors.lastname: Duno
authors.forename: Tina D
authors.initials: TD
authors.lastname: Jeppesen
authors.forename: John
authors.initials: J
authors.lastname: Vissing
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology; D001665:Binding Sites; D001706:Biopsy; D004576:Electromyography; D005260:Female; D018737:Hand Strength / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength; D053581:Muscle Strength Dynamometer; D018908:Muscle Weakness / Q000473:pathology; D018482:Muscle, Skeletal / Q000473:pathology*; D009222:Myotonia / Q000473:pathology; D009223:Myotonic Dystrophy / Q000235:genetics* / Q000473:pathology*; D010042:Ouabain / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics / Q000378:metabolism; D018911:Trinucleotide Repeats; D055815:Young Adult
chemical_list: D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase