Supplementary Material for: Membranoproliferative Glomerulonephritis Due to HACEK Endocarditis in a Patient with Cirrhosis: A Case Report

Introduction: Membranoproliferative glomerulonephritis (MPGN) is a rare pattern of glomerular injury that may be immune complex-mediated (ICM), most often secondary to infections, autoimmune disorders, or hematologic or less often solid tumor malignancies. Infections with HACEK (Haemophilus, Aggregatibacter, Cardiobacterium, Eikenella, Kingella) organisms are a well-known but rare cause of infective endocarditis (IE), which may be difficult to detect. Bacterial infections are more common in patients with cirrhosis, which may complicate the interpretation of clinical findings.
Case Presentation: The patient is a 44-year-old male with alcoholic cirrhosis who presented with hematuria, proteinuria and acute kidney injury (AKI), with negative blood cultures. Kidney biopsy revealed ICM-MPGN, with no underlying etiology identified. His clinical course was complicated by recurrent fluid overload with AKI requiring dialysis. Following corticosteroid therapy for ICM-MPGN, he developed Aggregatibacter bacteremia associated with worsening mitral regurgitation but without vegetations. After prolonged antibiotic therapy, the mitral valve was replaced and showed healed endocarditis. Following the antibiotic therapy and successful surgical intervention, his kidney function improved, and he remains dialysis independent.
Conclusion: This case highlights the role of HACEK organisms causing subclinical and difficult to diagnose IE which may induce ICM-MPGN, the increased risk of infection in patients with cirrhosis, and the need for a thorough evaluation for infectious etiologies in patients with ICM-MPGN prior to immunosuppressive therapy.