Redefining outcomes in immune TTP: an international working group consensus report.

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is a potentially fatal thrombotic microangiopathy caused by autoantibody-mediated severe deficiency of ADAMTS13. Standardized definitions of response, exacerbation, remission, and relapse were initially proposed in 2003 and modified by the International Working Group for TTP in 2017. These definitions, which have been widely used in clinical practice and research, are based primarily on the platelet count and are benchmarked against the timing of discontinuation of therapeutic plasma exchange (TPE). They do not incorporate ADAMTS13 activity or the temporizing effects on the platelet count of caplacizumab, a novel anti-von Willebrand factor (VWF) nanobody. In light of these limitations, the IWG aimed to develop revised consensus outcome definitions that incorporate ADAMTS13 activity and the effects of anti-VWF therapy, by using an estimate-talk-estimate approach. The updated definitions distinguish clinical remission and clinical relapse (defined primarily by platelet count) from ADAMTS13 remission and ADAMTS13 relapse (defined by ADAMTS13 activity). The revised definitions of exacerbation and remission are benchmarked against not only the timing of discontinuation of TPE but also that of anti-VWF therapy. Retrospective validation of the revised definitions is described, although they have yet to be prospectively validated. Clinical implications of the updated outcome definitions are also discussed and an example of their application to clinical practice is provided to highlight their clinical relevance.

Human protein C concentrates for replacement therapy in congenital and acquired protein C deficiency.

The protein C pathway has an important function in regulating and modulating blood coagulation and ensuring patency of the microcirculation. Protein C deficiency leads to macro- or microvascular thrombosis. Hereditary severe protein C deficiency is a life-threatening state with neonatal purpura fulminans. Patients with heterozygous protein C deficiency have an increased risk for thromboembolic events or coumarin-induced skin necrosis. Secondary protein C deficiency occurs during disseminated intravascular coagulation (DIC), sepsis (especially meningococcal sepsis with purpura fulminans), liver failure and vitamin K deficiency. Replacement with protein C concentrates is an established treatment for congenital protein C deficiency. The high-purity, plasma-derived protein C concentrate Ceprotin (Baxter AG, Vienna, Austria) is approved for this indication, but its use in acquired deficiency states is not approved. Several case series demonstrated beneficial effects in infectious purpura fulminans and DIC, but no controlled studies for these indications exist. Protein C concentrate may therefore be given off-label in such cases. Protein C concentrate has an excellent safety profile: no drug interactions, overdose or bloodborne infections, bleeding or prothrombotic complications have been observed. As with all protein preparations, a potential risk of hypersensitivity reactions exists.

Severe congenital protein C deficiency: the use of protein C concentrates (human) as replacement therapy for life-threatening blood-clotting complications.

The protein C pathway has an important function in regulating and modulating blood coagulation and ensuring patency of the microcirculation. Protein C deficiency leads to macro- and microvascular thrombosis. Congenital severe protein C deficiency is a life-threatening state with neonatal purpura fulminans and pronounced coagulopathy. Patients with heterozygous protein C deficiency have an increased risk for thromboembolic events or experience coumarin-induced skin necrosis during initiation of coumarin therapy. Replacement with protein C concentrates is an established therapy of congenital protein C deficiency, resulting in rapid resolving of coagulopathy and thrombosis without reasonable side effects. This article summarizes the current knowledge on protein C replacement therapy in congenital protein C deficiency.