Anti-Glomerular Basement Membrane Antibody Disease Complicated by Complement-Mediated Thrombotic Microangiopathy: A Case Report.

Anti-glomerular basement membrane (GBM) antibody disease rarely causes thrombotic microangiopathy (TMA). We herein report the case of a 75-year-old Japanese woman who developed refractory TMA during treatment for anti-GBM antibody disease. Although secondary TMA was initially suspected, persistent hemolytic anemia and thrombocytopenia despite plasma exchange, glucocorticoids, and cyclophosphamide led us to suspect complement-mediated TMA. Eculizumab was initiated after genetic testing for complement regulatory factors was performed. The patient became transfusion-independent within one week, and genetic testing identified the c.293C＞T (p.Thr98Ile) variant in CD46. Complement-mediated TMA should thus be considered in refractory cases, and anti-C5 monoclonal antibodies may be an effective therapeutic option.