A non-thrombocytopenic bleeding disorder due to an IgG4-kappa anti-GPIIb/IIIa autoantibody.
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.
McMillan
R
R
Scripps Research Institute, Lajolla, California 92037, USA.
Bowditch
R D
RD
Tani
P
P
Anderson
H
H
Goodnight
S
S
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*
D001323:Autoantibodies; D005353:Fibronectins; D007145:Immunoglobulin kappa-Chains; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D005340:Fibrinogen