Limitations of ADAMTS-13 activity level in diagnosing thrombotic thrombocytopenic purpura in pregnancy.

In pregnancy, it may be difficult to differentiate the syndrome of hemolysis, elevated liver enzymes, and low platelets from thrombotic thrombocytopenia purpura. Severely depressed (<5%) or absence of a disintegrin and metalloproteinase with thrombospondin motifs-13 activity levels are associated with thrombotic thrombocytopenia purpura and mildly decreased levels are associated with other disease processes, including pre-eclampsia and hemolysis, elevated liver enzymes, and low platelets syndrome. We present a case of a patient that presented at 20 weeks gestation with elevated liver enzymes and thrombocytopenia. The diagnosis was unclear at the time of presentation. She underwent induction of labor, and during the postpartum course, she was eventually diagnosed with thrombotic thrombocytopenia purpura; however, her activity level of a disintegrin and metalloproteinase with thrombospondin motifs-13 was only moderately depressed at 15% (normal pregnancy value 41%-105%).