How I diagnose and treat atypical hemolytic uremic syndrome.

Our understanding and management of atypical haemolytic uremic syndrome (HUS) has dramatically improved in the last decade. Atypical HUS has been established as a prototypic disease resulting from a dysregulation of the complement alternative C3 convertase. Subsequently, prospective non-randomized studies and retrospective series have shown the efficacy of C5 blockade in the treatment of this devastating disease. C5 blockade has become the cornerstone of the treatment of atypical HUS. This therapeutic breakthrough has been mitigated by persistent difficulties in the positive diagnosis of atypical HUS, and the latter remains, to date, a diagnosis by exclusion. Furthermore, the precise spectrum of complement-mediated renal thrombotic microangiopathy is still a matter of debate. Nevertheless, long-term management of atypical HUS is increasingly individualized and life-long C5 blockade is no more a paradigm that applies to all patients with this disease. The potential benefit of complement blockade in other forms of HUS, notably secondary HUS, remains uncertain.