Thrombotic microangiopathies: An illustrated review

The thrombotic microangiopathies (TMAs) are a heterogenous group of disorders with distinct pathophysiologies that cause occlusive microvascular or macrovascular thrombosis, and are characterized by microangiopathic hemolytic anemia, thrombocytopenia, and/or end‐organ ischemia. TMAs are associated with significant morbidity and mortality, and data on the management of certain TMAs are often lacking. The nomenclature, classification, and management of various TMAs is constantly evolving as we learn more about these rare syndromes. Thorough clinical and laboratory evaluation is essential to distinguish various TMAs and arrive at an accurate diagnosis, which is key for appropriate management. In this illustrated review, we focus on thrombotic thrombocytopenic purpura (TTP), Shiga toxin–associated hemolytic uremic syndrome, complement‐mediated hemolytic uremic syndrome, hematopoietic cell transplant‐associated TMA, and drug‐induced TMA, and describe their incidence, pathophysiology, diagnosis, and management. We also highlight emerging complement‐directed therapies under investigation for the management of complement‐mediated TMAs.