title: Electrically active immune-mediated rippling muscle disease preceding breast cancer.
abstract: BACKGROUND
  Rippling muscle disease (RMD) is a rare disorder of muscle hyperexcitability clinically characterized by painful muscle stiffness, rippling phenomenon, percussion-induced muscle mounding, and rapid contraction. RMD is typically considered to be electrically silent, but electrical activity during the muscle rippling has been occasionally described. RMD could be genetically determined or immune-mediated (iRMD). The association between cancer and iRMD is extremely rare.
  
  
  METHODS
  We present here a patient with electrically active iRMD preceding the diagnosis of breast cancer. The patient had acetylcholine receptor binding antibodies but no clinical or electrophysiological signs of myasthenia. Muscle biopsy revealed inflammatory changes and a mosaic distribution of sarcolemmal caveolin-3 deficiency. Sequencing of caveolin-3 gene detected no mutation. Immunotherapy led to the resolution of the RMD and disappearance of the serum acetylcholine receptor antibodies.
  
  
  CONCLUSIONS
  The abnormal electrical activity in this patient suggests that an acquired neuromuscular hyperexcitability syndrome represents a continuum of disorders. The close temporal relationship between the onset of iRMD and the diagnosis of breast cancer raises the possibility that iRMD might be paraneoplastic.
authors.affiliation: Department of Neurology, Mayo Clinic, Rochester, MN 55905, USA.
authors.forename: Teerin
authors.initials: T
authors.lastname: Liewluck
authors.forename: Brent P
authors.initials: BP
authors.lastname: Goodman
authors.forename: Margherita
authors.initials: M
authors.lastname: Milone
mesh_terms: D000368:Aged; D000970:Antineoplastic Agents / Q000627:therapeutic use; D001943:Breast Neoplasms / Q000150:complications / Q000175:diagnosis* / Q000188:drug therapy; D051244:Caveolin 3 / Q000235:genetics; D004560:Electricity; D004576:Electromyography; D005260:Female; D006801:Humans; D007136:Immunoglobulins / Q000627:therapeutic use; D018482:Muscle, Skeletal / Q000276:immunology* / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D009135:Muscular Diseases / Q000150:complications / Q000188:drug therapy / Q000276:immunology* / Q000378:metabolism; D009431:Neural Conduction / Q000502:physiology; D009460:Neurologic Examination; D011241:Prednisone / Q000627:therapeutic use; D011978:Receptors, Nicotinic / Q000276:immunology
chemical_list: D000970:Antineoplastic Agents; C417736:CAV3 protein, human; D051244:Caveolin 3; D007136:Immunoglobulins; D011978:Receptors, Nicotinic; D011241:Prednisone