A Novel Variant on the Thrombospondin Type-1 Repeat 2 Domain of ADAMTS13 in a Parturient with Suspected Hereditary Thrombotic Thrombocytopenic Purpura and Unusually High ADAMTS13 Activity.

Thrombotic thrombocytopenic purpura (TTP) represents a severe form of thrombotic microangiopathy that is caused by congenital or acquired absence or severe de fi ciency of the plasma metalloprotease ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13), which is required for cleavage of von Willebrand factor (VWF) multimers. 1 If highmolecular weight VWF is unableto degrade properly, its accumulation can result in micropla-telet thrombosis that obstructs microcirculation and leads to organ damage. Red blood cell (RBC) fragments can also arise due to mechanical shearing. Accumulated abnormalities can lead to serious consequences of platelet depletion, micro-vascular occlusion, hemolytic anemia due to erythrocyte rupture, and concurrent tissue ischemia. The mortality of TTP can exceed 80% without prompt diagnosis and treat-ment. However, timely identi fi cation and intervention with plasma exchange or transfusion can dramatically reduce the mortality rates to 10 to 20%. 2