Eculizumab in Hypertensive Emergency-associated Hemolytic Uremic Syndrome

Hemolytic and uremic syndrome (HUS) is a clinic-biological syndrome related to thrombotic microangiopathy affecting predominantly the kidney. Atypical HUS (aHUS) has been historically defined as HUS occurring in the absence of infectious event. The role of complement dysregulation in aHUS pathophysiology has been largely demonstrated, since C genetic rare variants are present in 60-70% aHUS patients. In line with the frequency of C dysregulation in aHUS, Eculizumab, an anti-C5 monoclonal antibody, has dramatically improved aHUS patients prognosis. Numerous conditions have been associated with aHUS, including hypertensive emergency (HE), a syndrome of acute blood pressure flare associated with end-organ damage. In cases of HE-aHUS, whether primary aHUS is complicated by secondary HE, or primary HE leads to secondary aHUS is still debated. The investigators recently demonstrated that C genetic variants frequency was similar in patients with HE-aHUS and patients with aHUS without HE, suggesting a major role for C dysregulation in HE-aHUS. Consequently, the investigators propose to evaluate, in HE-aHUS patients, the benefit of a strategy with early Eculizumab therapy (used within its marketing authorization and its conditions of refunding by the health insurance in usual care), compared to standard of care including tight blood pressure control. The hypothesis suggests that C dysregulation may impact renal prognosis of HE-aHUS patients. The investigator's aim to demonstrate that early Eculizumab therapy improves prognosis of HE-aHUS patients. Method The HYPERSHU study is a randomized, controlled, open-labelled study including HE-aHUS patients with severe AKI and no evidence of other conditions associated with HUS (infections, autoimmunity, drugs, pregnancy). The investigators plan to include 62 patients. Patients will be randomized in 2 arms: * Early Eculizumab therapy (for 3 months) added to standard of care (tight blood pressure control). * Standard of care alone with tight blood pressure control. Renal function after 6 months is the primary evaluation criterium. HE is a frequently associated with aHUS, and strongly impacts patient renal prognosis. Efficient therapeutic strategies are still lacking for this condition. The HYPERSHU study will allow to evaluate the benefit of early Eculizumab therapy in patients with HE-aHUS and severe renal dysfunction.