Thrombotic Thrombocytopenic Purpura/Hemolytic-Uremic Syndrome/Atypical Hemolytic-Uremic Syndrome

Thrombotic thrombocytopenic purpura (TTP) is a potentially fatal disorder characterized by acute episodes of systemic microvascular thrombosis and is associated with the presence of a severe deficiency of a disintegrin and metalloproteinase with thrombospondin motif member 13 (ADAMTS13) (activity <10%). ADAMTS13 deficiency is the only specific marker for TTP which can be acquired when autoantibodies to ADAMTS13, as demonstrated by positive anti-ADAMTS13 IgG identified in ∼75% of acute phase TTP or inherited (Upshaw-Schulman syndrome [USS]). The annual prevalence of TTP is ∼10 cases/million people and an annual incidence of ∼1–13 new case/million people. Peak incidence is between 30 and 50 years for acquired form. Congenital forms are seen in children. Predisposing factors include higher rates in women and African American race, HLA DR1*11, and obesity. Precipitating factors to increase Von Willebrand Factor (VWF) levels are inflammation, pregnancy, infections.