Concurrent Presentation of C3 Glomerulopathy and Benign Intracranial Hypertension in a Young Woman: A Case Report

Background: C3 glomerulopathy (C3G) is a rare complement-mediated glomerular disease characterized by dysregulation of the alternative complement pathway, leading to C3-dominant glomerular deposits and variable renal manifestations. Benign intracranial hypertension (BIH), or idiopathic intracranial hypertension, presents with increased intracranial pressure in the absence of structural lesions. While BIH has been reported in association with immune-complex glomerulonephritis, its co-occurrence with C3G has not been previously described. Case presentation. We report the case of a 25-year-old Asian woman presenting with a two-week history of progressive occipital headache, vomiting, and subsequent diplopia and blurred vision. Examination revealed bilateral papilledema and sixth nerve palsy. MRI findings and elevated lumbar puncture opening pressure (>25 cm H₂O) confirmed BIH, and acetazolamide was initiated with gradual improvement in symptoms. Routine investigations revealed renal dysfunction, non-nephrotic proteinuria, thrombocytopenia, and low C3 with normal C4. Renal biopsy demonstrated crescentic mesangioproliferative glomerulonephritis with C3-dominant deposits on immunofluorescence, confirmed by electron microscopy. Complement analysis showed reduced factor H levels. She was treated with prednisolone, mycophenolate mofetil, and a renin-angiotensin system blocker, with partial improvement in renal and neurological status. Genetic testing revealed a CFH variant of uncertain significance. Given her partial response and evidence of complement dysregulation, eculizumab is planned if no further improvement is observed. Conclusions: This is, to our knowledge, the first reported case of concurrent C3G and BIH. The coexistence of these conditions suggests a potential shared immunopathogenic pathway involving alternative complement pathway dysregulation, with possible effects on both renal and central nervous system vasculature. This case highlights the importance of considering intracranial hypertension in patients with C3G presenting with visual symptoms or headache and supports further research into complement-mediated mechanisms linking renal and neurological disease.