Background: Thrombotic thrombocytopenic purpura (TTP) is a severe disease with microthrombi in various organs. The idopathic subtype is characterized by reduced ADAMTS13 activity mediated via autoantibodies against this protease. Induction of autoantibodies mechanistically is incompletely understood, but certain drugs can induce anti-ADAMTS13 antibodies through hapten mechanisms.
Case report: A 56-year-old man was admitted from an external hospital because of a rapidly worsening general condition, hemolytic anemia (hemoglobin 4.17 mmol/l, hematocrit 0.19), and thrombocytopenia (22 Gpt/l) for unknown reasons. Additionally, he was found to have an elevated lactate dehydrogenase (45.37 μmol/l/s). 13 days before hospitalization he had received vaccination against H1N1. Laboratory tests revealed an increased total bilirubin (126 μmol/l), and a decreased haptoglobin level (< 0.08 g/l). The blood smear showed 24% fragmentocytes. Direct and indirect Coombs test were negative. TPP was diagnosed based on the clinical presentation and the detection of ADAMTS13 antibodies. Despite daily plasma exchange via plasmapheresis and administration of corticosteroids, there was no significant rise in platelet counts. Immunosuppression with a total of four weekly doses of rituximab (375 mg/m(2) body surface area) was added. Over the next 5 weeks, the platelet count very slowly rose. After a total of 46 sessions, plasmapheresis was ended with complete remission of the disease.
Conclusion: This report emphasizes the immunologic susceptibility of TTP, and suggests the potential, but not proven role of H1N1 vaccination in the pathogenesis of TTP, because no serum before vaccination was available. Severe autoantibody TTP can be successfully treated by administering rituximab in addition to standard treatment with plasmapheresis and corticosteroids.