title: Expanding the spectrum of monoclonal light chain deposition disease in muscle.
abstract: BACKGROUND
  The diagnosis of amyloid myopathy is delayed when monoclonal gammopathies are not detected on initial testing and muscle biopsies are nondiagnostic, and the EMG and symptoms can mimic an inflammatory myopathy.
  
  
  METHODS
  Case report of a patient presenting with severe progressive muscle weakness of unclear etiology despite an extensive workup including two nondiagnostic muscle biopsies.
  
  
  RESULTS
  Directed by MRI, a third biopsy revealed amyloid angiopathy and noncongophilic kappa light chain deposition in scattered subsarcolemmal rings and perimysial regions. A serum free light chain (FLC) assay revealed a kappa monoclonal gammopathy, which was not detected by multiple immunofixations.
  
  
  CONCLUSIONS
  The spectrum of immunoglobulin deposition in muscle is similar to other organs. It comprises a continuum that includes parenchymal amyloid deposition, amyloid angiopathy, and noncongophilic Light Chain Deposition Disease (LCDD). We recommend including the FLC assay in the routine investigation for monoclonal gammopathies. This case also highlights the value of MRI-guided muscle biopsy.
authors.affiliation: Department of Neurology, Johns Hopkins School of Medicine, 733 N. Broadway, Baltimore, Maryland 21205, USA.
authors.forename: Lyle W
authors.initials: LW
authors.lastname: Ostrow
authors.forename: Andrea M
authors.initials: AM
authors.lastname: Corse
authors.forename: Brett M
authors.initials: BM
authors.lastname: Morrison
authors.forename: Carol A
authors.initials: CA
authors.lastname: Huff
authors.forename: John A
authors.initials: JA
authors.lastname: Carrino
authors.forename: Ahmet
authors.initials: A
authors.lastname: Hoke
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Mammen
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000368:Aged; D000686:Amyloidosis / Q000097:blood / Q000209:etiology; D001706:Biopsy; D003224:Congo Red; D006801:Humans; D007147:Immunoglobulin Light Chains / Q000097:blood*; D007145:Immunoglobulin kappa-Chains / Q000378:metabolism; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000473:pathology; D010265:Paraproteinemias / Q000097:blood* / Q000150:complications / Q000473:pathology*
chemical_list: D007147:Immunoglobulin Light Chains; D007145:Immunoglobulin kappa-Chains; D003224:Congo Red; D000251:Adenosine Triphosphatases