[Diagnosis and treatment of thrombotic thrombocytopenic purpura]

Thrombotic thrombocytopenic purpura (TTP) is a life-threatening disease in which platelets are consumed and thrombotic microangiopathy develops in multiple organs due to a severe deficiency of the metalloproteinase, ADAMTS13. TTP should be suspected in any case associated with thrombocytopenia and hemolytic anemia; TTP can be diagnosed in cases of profound reduction in ADAMTS13 activity (to <10% of the normal level). Congenital TTP involves mutations in the ADAMTS13 gene, whereas acquired or autoimmune TTP results from the actions of inhibitory autoantibodies against the ADAMTS13 protein. Plasma exchange together with corticosteroids is an effective treatment for acquired TTP; plasma exchange removes autoantibodies and provides ADAMTS13 supplementation, whereas corticosteroids further suppress autoantibody generation. Rituximab was recently approved in Japan for use in refractory or relapsing TTP. Likewise, caplacizumab, an anti-von Willebrand factor, may contribute to disease control and overall survival by preventing ongoing thrombosis and acute end-organ damage.