[Atypical hemolytic uremic syndrome: key points in differential diagnosis and recent advances in treatment]

Atypical hemolytic uremic syndrome (aHUS) is a form of thrombotic microangiopathy (TMA) caused by endothelial injury resulting from dysregulated activation of the alternative complement pathway. Clinical outcomes have markedly improved since the anti-complement agent eculizumab, an anti-C5 monoclonal antibody, became available in 2013. However, no established diagnostic method directly assesses complement activation for definitive diagnosis. In practice, diagnosis relies on the evaluation of pathogenic variants in complement-related genes as predisposing factors and on the exclusion of other diseases that can cause TMA. Consequently, distinguishing aHUS from secondary TMA can sometimes be clinically challenging. In particular, secondary TMA associated with hypertensive emergencies or pregnancy may overlap with aHUS, requiring careful diagnostic consideration. In recent years, several novel anti-complement agents have been developed. In addition to therapies targeting the terminal complement pathway downstream of C5, agents that act on the proximal complement cascade are also under development, and further clinical evidence on these strategies is awaited.