Atypical haemolytic uraemic syndrome (aHUS) is a rare and life-threatening disease caused by complement system dysregulation leading to uncontrolled complement activation and thrombotic microangiopathy. We report the case of an adult patient with plasmaphaeresis-resistant aHUS and hypertension treated with the complement inhibitor eculizumab. Eculizumab was shown to completely inhibit haemolysis, normalize thrombocyte levels and increase diuresis. Full recovery of renal function was not possible due to irreversible renal damage prior to eculizumab initiation. These findings highlight the importance of early treatment with eculizumab in patients with poor response to standard therapy, in order to avoid irreversible renal damage.