There is a severe deficiency of ADAMTS13 activity (either from an inherited defect or inhibited function caused by the development of autoantibodies) resulting in decreased ability to cleave von Willebrand factor (vWF). Consequently, large vWF multimers accumulate and are released into blood where they bind to platelets to produce aggregates that form microthrombi within small arterioles and capillaries. These microthrombi induce tissue ischaemia, infarction, platelet consumption, and MAHA4.
