TTP is a blood disorder that causes microscopic clots in the small vessels.58 HIV may be a direct precipitant of TTP through damage of vascular endothelial cells resulting in dysfunction, localized thrombin generation, and consumption of ADAMTS13 (a metalloprotease enzyme that cleaves von Willebrand factor).59 Diagnosis of TTP requires 2 major criteria (e.g., thrombocytopenia, microangiopathic hemolytic anemia, and neurologic signs) and at least 2 minor criteria (fever, renal dysfunction, presence of thrombi in the circulation, and elevated lactate dehydrogenase). This evidence concerns the gene ADAMTS13 and congenital thrombotic thrombocytopenic purpura.