LAUSR

The emergence of specific treatment of atypical hemolytic uremic syndrome (aHUS) using eculizumab has allowed renal function recovery and safe kidney transplantation (KT). Early and precise recognition of complement-mediated (CM) atypical HUS (aHUS) is challenging and differs between children and adults. Our aim is to facilitate a decision-making process on HUS management. Hemolytic uremic syndrome (HUS) represents a heterogeneous group of diseases characterized by systemic endothelial cell injury, most often involving kidney, and which leads to thrombotic microangiopathy (TMA). Many inherited factors and environmental triggers cause HUS, but in children and the young, 90% are related to Shiga toxin-producing-Escherichia coli (STEC). Most non-STEC-HUS present primary complement (C) dysregulation and defective protection against C injury at the endothelial surface. Before eculizumab, CM-aHUS mortality was 60%, and progression to end stage kidney disease the rule, with frequent relapses after KT. Worldwide, the most common questions are who could benefit the most from C blockade, the most appropriate monitoring strategy for these individuals, and optimal duration of treatment with eculizumab. HUS is a life-threatening disease with poor outcome if untreated. Early and clear distinction between aHUS from other primary TMA (thrombotic thrombocytopenic-purpura, STEC-HUS), rare non-CM-aHUS, and secondary TMA is required as clinical features overlap. The current approach is terminology consensus, classification based on disease pathogenic mechanisms, and patient risk stratification.