title: Steroid-responsive type II anti-factor VIII:C autoantibody in a nonhemophiliac child.
abstract: Acquired antibodies to factor VIII:C in nonhemophiliac patients are uncommon in adulthood and exceedingly rare in childhood. We report a girl, 9 years of age, with no personal or familial bleeding history who presented with hematuria and bruising 2 weeks after an upper respiratory infection. The activated partial thromboplastin time was 71.9 s (normal, 25-40 s) and did not correct by mixing 1:1 with normal plasma, suggesting the presence of an inhibitor. Factor VIII:C levels were detectable at 0.03 U/ml, but inhibition experiments demonstrated the presence of an inhibitor with an activity of 24 Bethesda U/ml. This inhibitor was localized to the immunoglobulin (IgG) fraction of the patient's plasma. Incubation of the patient's IgG with normal pooled plasma resulted in a 66% decrease in factor VIII:C activity. Unlike the antibodies found in most hemophilia patients, the autoantibody produced by this patient demonstrated type II kinetics and did not inhibit all factor VIII:C activity even at very high concentrations. In addition, the rate of factor VIII:C inactivation by this autoantibody was much slower than that seen with type I inhibitors. The treatment of the patient with prednisone, 2.5 mg/kg/day, resulted in the rapid disappearance of detectable inhibitor and a rise in factor VIII:C levels to 0.70 U/ml. Normal factor VIII:C levels persisted after the discontinuation of steroids. This case is most unusual in that it occurred in a child without any evidence of an underlying autoimmune disorder, and unlike classical hemophiliac factor VIII:C inhibitors, there was a rapid response to steroids.
authors.affiliation: Department of Pathology, University of British Columbia, Vancouver.
authors.forename: C J
authors.initials: CJ
authors.lastname: Carter
authors.forename: D V
authors.initials: DV
authors.lastname: Devine
authors.forename: P C
authors.initials: PC
authors.lastname: Rogers
authors.forename: L D
authors.initials: LD
authors.lastname: Wadsworth
mesh_terms: D001323:Autoantibodies / Q000276:immunology*; D001327:Autoimmune Diseases / Q000188:drug therapy / Q000276:immunology*; D002648:Child; D005166:Factor V Deficiency / Q000209:etiology; D005169:Factor VIII / Q000276:immunology*; D005260:Female; D006417:Hematuria / Q000209:etiology*; D006801:Humans; D011241:Prednisone / Q000627:therapeutic use*; D011693:Purpura / Q000209:etiology*; D012141:Respiratory Tract Infections / Q000150:complications
chemical_list: D001323:Autoantibodies; D005169:Factor VIII; D011241:Prednisone