Factor V inhibitor associated with cold agglutinin disease.

An 81-year-old man known to have a stable cold agglutinin syndrome presented with a progressive cerebral hemorrhage. Coagulation tests revealed prolonged APTT and prothrombin time and severely decreased factor V activity, which could not be normalized by mixing with normal plasma. The patient appeared refractory to substitution with fresh-frozen plasma, suggesting the presence of a circulating inhibitor specific for factor V. To our knowledge, this is the first case of a lymphoproliferative disease leading to a cold agglutinin syndrome and a putative inhibitor of factor V. In patients with paraproteinemia presenting with bleeding diathesis, the presence of a circulating inhibitor of a specific coagulation factor must be considered.