[Coagulopathy with autoantibodies to blood-clotting factors: overview and laboratory diagnosis]

The acquired inhibitors of blood clotting-factors are immunoglobulins that directly inhibit clotting factors or accelerate their clearance from circulation. The majority of inhibitors are directed against factor VIII, which arises spontaneously in healthy elderly, postpartum women, patients with autoimmune disorders or malignancy, and those with various underlying disorders. The most common initial symptom is bleeding into the skin or muscles spontaneously or caused by minor trauma, which sometimes extends to cause severe anemia. Those with acquired hemophilia may not receive a first consultation by a hematologist, resulting in delayed laboratory diagnosis. The activated partial thromboplastin time (APTT) of the hemophilia patient's plasma is prolonged, and is not corrected by mixing with normal plasma for 2 hours. The mixing test provides suggestive evidence of a factor VIII inhibitor, but can not distinguish lupus anticoagulant. Although the factor VIII activity of plasma is remarkably low, the activities of other intrinsic clotting factors can also be reduced apparently in the one-stage assay. A quantitative inhibitor measurement assay is required to confirm that the inhibitor acts specifically on factor VIII.