Immune Thrombotic Microangiopathy: An Unusual Complication of Novel Anticancer Therapy

Thrombotic microangiopathy (TMA) and thrombotic thrombocytopenic purpura (TTP) are rare potentially life-threatening complications in the oncology setting. The rapid approval of new drugs in oncology brings challenges since these can cause TMA/TTP by unexpected mechanisms. Additionally, confounding factors in oncology patients like sepsis and coagulopathy make recognition of TMA difficult. Trastuzumab–emtansine (TDM1) is a HER2-targeted antibody–drug conjugate. The antibody is the anti-HER2 IgG1 trastuzumab, and the cytotoxin emtansine (DM1) is a microtubule inhibitor. TTP has not been reported with TDM1 therapy previously. Here, we discuss a patient with breast cancer who developed immune-mediated TMA/acquired TTP after her therapy was switched from trastuzumab to TDM1 and was treated successfully with plasmapheresis and rituximab.