C5 and lymphoma: Recently, abnormalities in the complement system have been identified in the pathogenesis of TA-TMA, and there are series of reports stating that anti-C5 monoclonal antibody (eculizumab) is effective in patients with high levels of the membrane attack complex (C5b-9).<h4>Case presentation</h4>A 12-year-old boy underwent autologous BMT after receiving high-dose chemotherapy for malignant lymphoma.