title: A non-thrombocytopenic bleeding disorder due to an IgG4-kappa anti-GPIIb/IIIa autoantibody.
abstract: Autoantibodies in chronic immune thrombocytopenic purpura occasionally interfere with platelet function. We describe a patient with a normal platelet count who had clinically significant mucosal bleeding, a prolonged bleeding time and abnormal platelet aggregation. The patient had high titres of an IgG4 kappa autoantibody, directed to a cation-dependent epitope on platelet glycoprotein IIb/IIIa, which blocked the binding of fibrinogen and fibronectin to this complex. Corticosteroid treatment resulted in clinical improvement and a marked drop in autoantibody concentration. The lack of thrombocytopenia in this patient, despite high autoantibody levels, is best explained by the poor recognition of IgG4 antibodies by phagocytic cells.
authors.affiliation: Scripps Research Institute, Lajolla, California 92037, USA.
authors.forename: R
authors.initials: R
authors.lastname: McMillan
authors.forename: R D
authors.initials: RD
authors.lastname: Bowditch
authors.forename: P
authors.initials: P
authors.lastname: Tani
authors.forename: H
authors.initials: H
authors.lastname: Anderson
authors.forename: S
authors.initials: S
authors.lastname: Goodnight
mesh_terms: D001323:Autoantibodies / Q000276:immunology*; D001760:Bleeding Time; D003108:Colonic Diseases / Q000209:etiology* / Q000276:immunology; D005340:Fibrinogen / Q000378:metabolism; D005353:Fibronectins / Q000378:metabolism; D006471:Gastrointestinal Hemorrhage / Q000209:etiology* / Q000276:immunology; D006801:Humans; D007145:Immunoglobulin kappa-Chains / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D010974:Platelet Aggregation; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000276:immunology*
chemical_list: D001323:Autoantibodies; D005353:Fibronectins; D007145:Immunoglobulin kappa-Chains; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D005340:Fibrinogen