Thrombotic Microangiopathy Syndromes-Common Ground and Distinct Frontiers

Thrombotic microangiopathies (TMAs) have in common a terminal phenotype of microangiopathic hemolytic anemia with end-organ dysfunction. Thrombotic thrombocytopenic purpura results from von Willebrand factor multimerization, Shiga toxin-mediated hemolytic uremic syndrome causes toxin-induced endothelial dysfunction, while atypical hemolytic uremic syndrome results from complement system dysregulation. Drug-induced TMA, rheumatological disease-induced TMA, and renal-limited TMA exist in an intermediate space that represents secondary complement activation and may overlap with atyp-ical hemolytic uremic syndrome clinically. The existence of TMA without microangiopathic hemolytic features, renal-limited TMA, represents an undiscovered syndrome that responds incompletely and inconsistently to complement blockade. Hemato-poietic stem cell transplant-TMA represents another more resistant form of TMA with different therapeutic needs and clinical course. It has become apparent that TMA syndromes are an emerging field in nephrology, rheumatology, and hematology. Much work remains in genetics, molecular biology, and therapeutics to unravel the puzzle of the relationships and distinctions apparent between the different subclasses of TMA syndromes. (C) 2022 The Authors. Published Elsevier Inc. on behalf of the National Foundation, Inc.

Automated summary

Thrombotic microangiopathies (TMAs) are a group of disorders characterized by microangiopathic hemolytic anemia and end-organ dysfunction. There are different types of TMAs, including thrombotic thrombocytopenic purpura, Shiga toxin-mediated hemolytic uremic syndrome, and atypical hemolytic uremic syndrome. Other forms of TMA, such as drug-induced TMA, rheumatological disease-induced TMA, and renal-limited TMA, exist in an intermediate space and may overlap with atypical hemolytic uremic syndrome clinically. Hematopoietic stem cell transplant-TMA is a more resistant form of TMA with different therapeutic needs and clinical course. The understanding of TMA syndromes is an emerging field in nephrology, rheumatology, and hematology, and further research is needed to unravel the relationships and distinctions between different subclasses of TMA syndromes.