Key Points Prospectively collected data on demographics, complications, and mortality are described for 4899 US men with severe hemophilia. Analyzing multiple birth cohorts of US men with severe and mild hemophilia demonstrates ongoing morbidity in need of surveillance.

Key Points• Joint hemorrhages and orthopedic procedures are more frequent in patients with hemophilia A than in those with hemophilia B.• FA levels of 20% may be required to prevent all joint hemorrhages.Data are needed on minimal factor activity (FA) levels required to prevent bleeding in hemophilia. We aimed to evaluate associations between hemophilia type and FA level and joint bleeding and orthopedic procedures using longitudinal data. Data were collected over an 11-year period on males with nonsevere hemophilia A or B without inhibitors who were receiving on-demand factor replacement therapy. Data on the number of joint bleeds in the previous 6 months and data on procedures from clinical records were analyzed using regression models. Data were collected on 4771 patients (hemophilia A, 3315; hemophilia B, 1456) from 19 979 clinic visits. Ages ranged from 2 to 91 years and baseline FA level ranged from 1% to 49% with a mean of 9.4%. Joint bleeding rates were heterogeneous across the FA range and were highest among men age 25 to 44 years. Adjusted for FA level, the mean number of joint bleeds per 6 months was 1.4 and 0.7 for patients with hemophilia A and B, respectively (P , .001). Regression models predicted 1.4 and 0.6 bleeds per year for hemophilia A and B patients, respectively, at an FA level of 15%. Patients with hemophilia B were 30% less likely than those with hemophilia A to have undergone an orthopedic procedure. We conclude that joint bleed rates for any given FA level were higher among hemophilia A than hemophilia B patients, and target FA levels of 15% are unlikely to prevent all joint bleeding in US males with hemophilia.

Platelet-associated TACO is greatly underestimated by passive reporting in the adult patient population.

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Insights into immune-mediated thrombotic thrombocytopenic purpura (iTTP) pathophysiology have led to novel targeted therapies. Immunomodulatory strategies target anti-ADAMTS13 antibodies: rituximab is effective in inducing responses in refractory/relapsed TTP and increasing relapse-free survival; caplacizumab targets the von Willebrand factor–platelet interaction to hasten platelet count recovery and reduce mortality and TTP-related ischemic events. Bortezomib and recombinant ADAMTS13 are under investigation. This review examines how targeted therapies are disrupting current treatment paradigms to improve outcomes of iTTP.