A Novel Homozygous CFH Variant Associated with Atypical Hemolytic Uremic Syndrome Triggered by Colorectal Cancer: A Case Report

Complement-mediated thrombotic microangiopathy (cmTMA), historically referred to as atypical hemolytic uremic syndrome, is driven by dysregulated alternative complement activation and is often unmasked by secondary triggers. A 40-year-old man with pre-existing hypertension (peak blood pressure: 145/94 mmHg) who presented with microangiopathic hemolytic anemia, severe thrombocytopenia, and acute kidney injury requiring hemodialysis is reported. Therapeutic plasma exchange was initiated while thrombotic thrombocytopenic purpura was being excluded, and eculizumab was started after meningococcal vaccination and antibiotic prophylaxis (900 mg weekly induction followed by biweekly maintenance). During the workup for recurrent hematochezia, a transverse colon adenocarcinoma was diagnosed and resected, without the need for adjuvant chemotherapy. Hematologic remission was achieved on eculizumab, and renal function partially recovered, allowing discontinuation of dialysis at 3 months. However, chronic kidney disease (CKD) persisted at the last follow-up (creatinine 2.17 mg/dL; estimated glomerular filtration rate(eGFR) 38 mL/min/1.73 m2; CKD stage 3b). Genetic analysis identified a homozygous CFH splice-site variant (c.1159+4A>C), supporting underlying complement dysregulation. This case highlights the importance of prioritizing genetic evaluation and modern nomenclature in cmTMA occurring in the context of malignancy.

Cite this article as: Gür MB, Özcan SG, Dinçer MT, et al. A novel homozygous CFH variant associated with atypical hemolytic uremic syndrome triggered by colorectal cancer: A case report. Cerrahpaşa Med J. 2026, 50, 0103, doi: 10.5152/cjm.2026.25103.