Background: Thrombotic thrombocytopenic purpura (TTP) is a rare and severe disease, characterized by thrombocytopenia, microangiopathic anaemia, fever, renal failure, and neurological manifestation caused by deposition of von Willebrand factor - platelet rich hyaline thrombi in the arterioles and capillaries. Plasma exchange has decreased the mortality in TTP from almost 100% to 10–30%. However, relapses occur in more than one-third of patients, a subset of whom develop multiple relapses or chronic disease requiring numerous sessions of plasma exchange. This treatment is costly and associated with many adverse reactions. Case

Report: We describe a female patient - diagnosed with TTP in 1996 - who did not achieve a sustained remission with plasma exchange, steroids and vincristine, but who remained in remission after a splenectomy performed in 1997. The patient underwent relapse in 2003 and restarted plasma exchange, with progressive improvement of cytopenias. Plasma exchange was reduced in frequency from daily sessions to every other day. There was a lowering of platelet levels and an increase in LDH levels - steroids and vincristine were re-initiated, but without response. The patient was treated with four, weekly doses (375 mg/m2) of rituximab. Plasma exchange was only required during the first 2 weeks of rituximab treatment, and was discontinued after the second dose of rituximab. The patient remained in complete remission for 9 months, but was then admitted to hospital with femoral thrombosis, and normal LDH and platelet levels. After 40 days of thrombosis therapy, the patient had a further relapse and refused plasma exchange. Treatment with rituximab was restarted as previously, and the patient achieved a complete remission within 2 weeks - now sustained for 11 months.

Conclusion: In comparing this patient with eight previous cases not treated with rituximab, we conclude that rituximab is a very effective treatment for TTP, which is not associated with clinically significant toxicity. Randomized clinical trials are required to confirm these findings.

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