An acquired, calcium-dependent, factor X inhibitor.
Acquired factor X (FX) deficiency unrelated to amyloidosis is a rare disorder in which an anti-FX antibody is infrequently detected. A patient with severe bleeding due to a calcium ion-dependent anti-FX IgG antibody is described. The FX affinity purified IgG bound the light chain of FX, but not FX lacking its γ-carboxyglutamic acid domain, and binding was enhanced >1000-fold in the presence of calcium ions. The antibody also recognized prothrombin and factor VII with about 100-fold and 1000-fold lower affinity. Like a lupus anticoagulant, increasing concentrations of phospholipids in functional assays reduced the inhibitory activity of the antibody. The effect of these properties of the inhibitor on laboratory diagnostic studies is considered.
Division of Hematology, Washington University School of Medicine, St. Louis, MO 63110, USA. Electronic address: gbroze@dom.wustl.edu.
George J
GJ
Broze
D000368:Aged; D001323:Autoantibodies / Q000097:blood / Q000276:immunology* / Q000302:isolation & purification / Q000378:metabolism; D001777:Blood Coagulation; D002118:Calcium / Q000378:metabolism; D005170:Factor X / Q000037:antagonists & inhibitors / Q000276:immunology*; D005171:Factor X Deficiency / Q000097:blood / Q000276:immunology / Q000378:metabolism; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism; D008297:Male; D010743:Phospholipids / Q000097:blood / Q000378:metabolism
D001323:Autoantibodies; D007074:Immunoglobulin G; D010743:Phospholipids; D005170:Factor X; D002118:Calcium
Acquired; Calcium-dependent; Factor X; Inhibitor