title: Phenotypic variability in rippling muscle disease.
abstract: OBJECTIVE
  To characterize the phenotype of hereditary rippling muscle disease (RMD) and to report the results of genetic linkage studies.
  
  
  BACKGROUND
  RMD is a rare autosomal-dominant inherited muscle disorder. Individuals complain of muscle stiffness, exercise-induced muscle pain, and cramp-like sensations. The characteristic feature of RMD is increased mechanical muscle irritability, which is electrically silent in electromyographic examinations.
  
  
  METHODS
  Forty-six individuals from two unrelated German kindreds with RMD were examined. Linkage analysis to the RMD locus on chromosome 1q41-q43 was performed.
  
  
  RESULTS
  In kindred A, 15 individuals from four generations, and in kindred B, four individuals from three generations had clinical features of RMD. The most consistent clinical findings were percussion-induced rapid muscle contractions (PIRCs) and muscle mounding, which were present in all 19 affected individuals. Only 12 individuals exhibited muscle rippling, indicating that rippling is not always present in RMD. Twelve of 19 individuals had muscle-related complaints, primarily exertional cramps and stiffness. The mean age at the onset of complaints was 22 years (range, 5 to 54 years). Seven of 19 individuals showed only mechanical-induced muscle irritability but did not have muscular symptoms. Genetic analysis excluded linkage to the RMD locus on chromosome 1q4 in both kindreds.
  
  
  CONCLUSIONS
  The phenotype of RMD is variable but generalized PIRCs are the most obvious and reliable clinical feature of RMD. Diagnostic criteria of RMD should include generalized PIRCs in addition to muscle mounding, rippling, and creatine kinase elevation.
authors.affiliation: Department of Neurology, Ruhr-University, Bochum, Germany. matthias.vorgerd@ruhr-uni-bochum.de
authors.forename: M
authors.initials: M
authors.lastname: Vorgerd
authors.forename: H
authors.initials: H
authors.lastname: Bolz
authors.forename: T
authors.initials: T
authors.lastname: Patzold
authors.forename: C
authors.initials: C
authors.lastname: Kubisch
authors.forename: J P
authors.initials: JP
authors.lastname: Malin
authors.forename: W
authors.initials: W
authors.lastname: Mortier
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D002878:Chromosomes, Human, Pair 1 / Q000235:genetics; D004594:Electrophysiology; D005260:Female; D008040:Genetic Linkage; D006801:Humans; D008297:Male; D008875:Middle Aged; D009132:Muscles / Q000503:physiopathology; D009135:Muscular Diseases / Q000235:genetics* / Q000503:physiopathology; D010375:Pedigree; D010641:Phenotype