Post-bone marrow transplant thrombotic microangiopathy

Thrombotic microangiopathy (TMA) is a systemic disease characterized by microangiopathic hemolytic anemia, thrombocytopenia and organ failure. Post-bone marrow transplant TMA (post-BMT TMA) is a life-threatening condition that has been reported to afflict between 0.5 and 63.6% of BMT patients. The incidence of post-BMT TMA is affected by evolving therapies such as conditioning regimens. The etiology of post-BMT TMA is thought to be multifactorial, including the effects of immunosuppressive agents, viral infections, TBI and GvHD. A growing body of evidence highlights the importance of complement system activation and endothelial damage in post-BMT TMA. Although plasmapheresis has commonly been used, its therapeutic rationale for the majority of post-BMT TMA cases is unclear in the absence of circulatory inhibitors. It has become possible to target complement activation with eculizumab, a drug that blocks the terminal complement pathway. Early studies have highlighted the importance of anti-complement therapies in treating post-BMT TMA. Moreover, finding complement gene mutations may identify patients at risk, but whether such patients benefit from prophylactic anti-complement therapies before BMT remains to be studied. This review focuses on diagnostic criteria, pathophysiology, treatment and renal outcomes of post-BMT TMA.