Complement Factor H Mutation-Associated Atypical Haemolytic Uraemic Syndrome Presenting With Dialysis-Dependent Renal Failure: A Case Report

A 57-year-old gentleman with no prior kidney disease presented with rapidly progressive acute kidney injury, anaemia, and hypertension. Initial investigations revealed severe acute kidney injury, microangiopathic haemolysis, and heavy proteinuria. Secondary causes of thrombotic microangiopathy (TMA), including Shiga toxin infection, autoimmune disease, malignant hypertension, and medication-induced injury, were systematically excluded. A renal biopsy demonstrated morphological features of TMA and helped exclude important mimics. Subsequent genetic testing identified a pathogenic complement factor H (CFH) splice site mutation, supporting a diagnosis of complement-mediated atypical haemolytic uraemic syndrome (aHUS). He required urgent dialysis. Following counselling and meningococcal vaccination, complement inhibition with eculizumab was offered, but the patient declined because of concerns about lifelong infection risk. He remains dialysis dependent. This case highlights the role of kidney biopsy in characterising injury and excluding mimics, the importance of recognising complement-mediated disease early, and the need for thoughtful, shared decision-making when treatment involves long-term immunological risk.