title: Relatively restricted migration of polyclonal IgG4 may mimic a monoclonal gammopathy in IgG4-related disease.
abstract: OBJECTIVE
  IgG4-related disease (IgG4-RD) is an increasingly recognized syndrome of unknown etiology that can affect a wide variety of organs. The commonly shared features include tumor-like swelling of the involved organs, a lymphoplasmacytic infiltrate enriched with polyclonal IgG4-positive plasma cells, variable degree of fibrosis, and elevated serum concentrations of polyclonal IgG4.
  
  
  METHODS
  In a qualitative retrospective study, the electrophoretic characteristics of serum from patients with increased polyclonal IgG4 were studied to see if a reproducible pattern could be identified.
  
  
  RESULTS
  We demonstrate that a characteristic focal band bridging the β and γ fraction by serum protein electrophoresis may be a first serologic indication for IgG4-RD. We further demonstrate that significant κ:λ skewing can occur in the polyclonal IgG4 fraction.
  
  
  CONCLUSIONS
  The focal band detected by electrophoresis in sera from patients with IgG4-RD can be confirmed as polyclonal by immunofixation or immunosubtraction. Because these bands may be predominately of one light chain isotype, they could be misinterpreted as monoclonal gammopathies.
authors.affiliation: From the Department of Laboratory Medicine, Radboud University Medical Center, Nijmegen, The Netherlands; Department of Tumor Immunology, Nijmegen Centre for Molecular Life Sciences, Nijmegen, The Netherlands; and H.Jacobs@Radboudumc.nl.
authors.forename: Joannes F M
authors.initials: JF
authors.lastname: Jacobs
authors.affiliation: From the Department of Laboratory Medicine, Radboud University Medical Center, Nijmegen, The Netherlands;
authors.forename: Renate G
authors.initials: RG
authors.lastname: van der Molen
authors.affiliation: Department of Pathology, University of Michigan Hospital and Health Systems, Ann Arbor.
authors.forename: David F
authors.initials: DF
authors.lastname: Keren
mesh_terms: D000368:Aged; D001327:Autoimmune Diseases / Q000175:diagnosis* / Q000276:immunology / Q000473:pathology; D003937:Diagnosis, Differential; D004586:Electrophoresis; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000032:analysis* / Q000097:blood / Q000276:immunology; D008297:Male; D008875:Middle Aged; D010265:Paraproteinemias / Q000175:diagnosis* / Q000276:immunology / Q000473:pathology; D010950:Plasma Cells / Q000276:immunology; D012189:Retrospective Studies
chemical_list: D007074:Immunoglobulin G
keywords: Electrophoresis; IgG subclasses; IgG4; IgG4-related disease; Migration