Rituximab for refractory and or relapsing thrombotic thrombocytopenic purpura related to immune-mediated severe ADAMTS13-deficiency: a report of four cases and a systematic review of the literature - Elliott, M A; Heit, J A; Pruthi, R K; Gastineau, D A; Winters, J L; Hook, C C (Eur J Haematol, 2009)