Mechanism of Factor X Deficiency in Systemic Amyloidosis

SOME patients with primary (immunoglobulintype) amyloidosis acquire a coagulation disorder characterized by factor X deficiency1 2 3 4 5 6 7 8 9 10 11 12 13 and occasionally factor IX deficiency.12 , 13 These patients may have hemorrhagic complications superimposed on the clinical manifestations of amyloidosis. We have previously demonstrated that the acquired factor X deficiency in this disorder is due to rapid clearance of factor X from the circulating blood, with immobilization of the protein in the vasculature.11 This observation explains why these patients are refractory to replacement therapy involving infusion of plasma and plasma fractions containing factor X. The direct binding of factor X to amyloid fibrils exposed to circulating blood . . .