Thrombotic thrombocytopenic purpura associated with systemic lupus erythematosus

Thrombotic thrombocytopenic purpura (TTP) occurring in patients with systemic lupus erythematosus (SLE) is rare and can be difficult to diagnose because of overlapping features of the two disorders. The aim of this study is to further characterize this uncommon association in terms of presenting features, diagnostic difficulties and treatment outcome. This is the largest series from a single centre with 6 patients diagnosed over a 6-year period. Two thirds of the patients had a simultaneous diagnosis of TTP and SLE. Half of the patients had a positive Coombs test along with clear features of TTP. Five patients received plasmapheresis as initial treatment while 1 patient received plasma infusions only. Four out of 5 patients responded to plasmapheresis and only 1 patient required cytotoxic therapy. TTP in association with SLE appears to be underdiagnosed and a positive Coombs test is not against the diagnosis of TTP in this setting. Most of the patients respond well to plasmapheresis. In case of a poor response, cytotoxic drugs should be considered early.