24yo with PMH SLE on plaquenil, autoimmune hemolytic anemia (initial flare 10 yrs ago, treated with steroids) who was admitted due to thrombocytopenia with platelet count 5. Further labs showing hgb 10.4, hapto <10, LDH 979, and tbili 2.2. Peripheral smear with schistocytes. Despite her labs, she was fully oriented with no neurologic symptoms and hemodynamically stable without any evidence of end organ damage. Plasmic score 7. She was started on methylprednisone and plasmapheresis was initiated with rapid improvement in platelet count. ADAMTS13 level 11% with inhibitor 0.7, confirming the diagnosis of TTP. Would you use Rituximab and/or Caplacizumab in this case and what helps guide that decision?
I would recommend using rituximab up-front in this case (and in most cases of TTP). Rituximab may lower the risk of rapid relapse following discontinuation of plasma exchange, as well as delayed relapse during/following steroid taper. Additionally, patients with underlying SLE may derive particular benefit (w/ respect to reduction of relapse risk) from rituximab. I do not recommend use of caplacizumab in most cases of TTP. I would typically only consider caplacizumab if there is c/f ongoing TTP related organ injury or ischemia. In all other settings, caplacizumab is likely not of signficant clinical benefit. Although caplacizumab has been shown to reduce length of hospitalization for TTP, it likely does not significantly modify overall response rate or risk of relapse (and the cost savings afforded by shorter length of hospitalization are likely cancelled out by the great expense of the drug). Would continue with plasma exchange and steroids as you are doing. Would also add rituximab (4 weekly infusions). Would not pursue caplacizumab.
