A comparison of thrombotic thrombocytopenic purpura in an inception cohort of patients with and without systemic lupus erythematosus

Objectives. To compare the clinical presentation, response to therapy and outcome of thrombotic thrombocytopenic purpura (TTP) in an inception cohort of patients with and without SLE. Methods. Medical records of patients diagnosed with TTP at Singapore General Hospital between January 2003 and December 2007 were reviewed. Results. Ten idiopathic TTP (iTTP) and eight SLE-associated TTP (sTTP) patients were identified, with iTTP patients being older (mean 50.4 vs 34.5 yrs). Five iTTP patients were ANA positive but did not have any features of SLE. All sTTP patients had active SLE at TTP diagnosis and had more renal involvement than iTTP (87.5% vs 50%). The mean duration from the first symptom suggestive of TTP to diagnosis was 7.7 days and 19.5 days in iTTP and sTTP patients. All patients received high-dose corticosteroids. Cytotoxic and immunosuppressive drugs were used more commonly (87.5% vs 50%) and earlier (Day 2/3 vs after Day 7) in sTTP patients. Vincristine was the drug of choice in iTTP and cyclophosphamide in sTTP. Three SLE patients received rituximab. Mortality for iTTP and sTTP was 50% (95% CI 19%, 81%) and 62.5% (95% CI 29%, 96%), respectively. The mean (s.d.) time to complete remission was 31.3 (± 26.4) days in sTTP (n = 3) and 16.8 (± 6.1) days in iTTP (n = 5). Conclusion. Despite early and more aggressive therapy in sTTP, mortality was higher and the time to complete remission were longer, suggesting that sTTP is more severe. The tempo of development of TTP in SLE patients was slower.