MCQ Hematology Answer 13

Answer: E

The history suggests a possible autoimmune disease (such as Systemic Lupus Erythematosis) as well as a lymphoma. The prolonged aPTT that only partially corrects with a 1:1 mixing study indicates an inhibitor, while the total correction of the prothrombin time on 1:1 mix suggests a deficiency. A lupus anticoagulant with an associated factor II (prothrombin) deficiency due to an antibody that complexes with prothrombin (affecting clearance but not affecting the active site of thrombin) will cause this pattern of laboratory results. von Willebrand disease would cause only a prolonged aPTT, and a factor V deficiency or inhibitor would not be expected to give this pattern of correction in the 1:1 mixing studies (either both assays would be corrected or both would not be corrected). DIC is unlikely because the aPTT is prolonged out of proportion to the prothrombin time and degree of thrombocytopenia, and the patient has no bleeding symptoms. Platelet antibodies, while they might be positive in this setting, would not account for the abnormal coagulation parameters.

References:

1. Fleck RA, Rapaport SI, Rao VM. Anti-prothrombin antibodies and the lupus anticoagulant. Blood 1988; 72:512-9.

2. Pernod G, Arvieux J, Carpentier PH, Pascal M, Bosson J Luc, Benoît P. Successful treatment of lupus anticoagulant-hypoprothrombinemia syndrome using intravenous immunoglobulins. Thromb Haemost 1997; 78:969-70.

Category: Hematology MCQs