title: Hypoglycemia due to an insulin binding antibody in a patient with an IgA-kappa myeloma.
abstract: BACKGROUND
  Autoantibodies to insulin have been described to cause spontaneous hypoglycemia in nondiabetic subjects. There have been occasional reports of spontaneous hypoglycemia due to monoclonal anti-insulin antibodies. We present the first report of a patient with an IgA-kappa myeloma in whom frequent hypoglycemia resulted from the ability of the monoclonal IgA-kappa to bind insulin.
  
  
  OBJECTIVE
  The aim of this study was to describe the occurrence of profound hypoglycemia in a patient with IgA-kappa myeloma, characterize biochemically the nature of the IgA:insulin complex present, and place this case in the context of the published literature on hypoglycemia resulting from autoantibodies to insulin.
  
  
  METHODS
  A case study was performed.
  
  
  METHODS
  A single case of profound hypoglycemia associated with IgA-kappa myeloma was studied.
  
  
  METHODS
  There were no interventions.
  
  
  METHODS
  A case study was performed.
  
  
  RESULTS
  Polyethylene glycol precipitation and gel filtration chromatography were used to demonstrate high-molecular weight insulin immunoreactivity in the patient's plasma. This was characterized as an insulin binding IgA-kappa paraprotein present at 4200 mg/dl (42 g/liter) with a relatively high insulin dissociation constant of 0.32 microm/liter using radiolabelled insulin binding studies.
  
  
  CONCLUSIONS
  We present the first case of hypoglycemia due to IgA binding insulin antibodies in a patient with an IgA-kappa paraprotein myeloma. The hypoglycemia was associated with high-plasma insulin levels and relatively low C-peptide levels. A plausible mechanism for the hypoglycemia is the delayed clearance of insulin. This case broadens the spectrum of monoclonal gammopathies that have been associated with anti-insulin reactivity and spontaneous hypoglycemia.
authors.affiliation: Department of Clinical Biochemistry, Addenbrooke's Hospital, Cambridge, UK. djh44@hermes.cam.ac.uk
authors.forename: D J
authors.initials: DJ
authors.lastname: Halsall
authors.forename: M
authors.initials: M
authors.lastname: Mangi
authors.forename: M
authors.initials: M
authors.lastname: Soos
authors.forename: M N
authors.initials: MN
authors.lastname: Fahie-Wilson
authors.forename: G
authors.initials: G
authors.lastname: Wark
authors.forename: R
authors.initials: R
authors.lastname: Mainwaring-Burton
authors.forename: S
authors.initials: S
authors.lastname: O'Rahilly
mesh_terms: D000368:Aged; D000918:Antibody Specificity; D001323:Autoantibodies / Q000097:blood / Q000276:immunology*; D002850:Chromatography, Gel; D006801:Humans; D007003:Hypoglycemia / Q000209:etiology / Q000276:immunology*; D007070:Immunoglobulin A / Q000097:blood / Q000276:immunology; D007145:Immunoglobulin kappa-Chains / Q000097:blood / Q000276:immunology; D007328:Insulin / Q000097:blood / Q000276:immunology*; D008297:Male; D009101:Multiple Myeloma / Q000150:complications / Q000276:immunology*
chemical_list: D001323:Autoantibodies; D007070:Immunoglobulin A; D007145:Immunoglobulin kappa-Chains; D007328:Insulin