ADAMTS13 and thrombotic thrombocytopenic purpura: Thrombotic thrombocytopenic purpura (TTP) is caused by severe deficiency of a thrombospondin type 1 motif, member 13 (ADAMTS13).[1] These patients commonly exhibit neurological involvement,[2] including stroke, epilepsy, spinal cord injury, or posterior reversible encephalopathy syndrome (PRES).