Abstract: FR-PO0447
AKI with Triple Positive Serology: A Diagnostic Challenge
Session Information
- AKI: Case Reports - TMA, Vasculitis, Immune-Mediated Injury, and Systemic Disease
October 23, 2026 | Location: Exhibit Hall A, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Acute Kidney Injury
- 102 AKI: Clinical, Outcomes, and Trials
Authors
- Ali, Haider, Tallaght University Hospital, Dublin, Leinster, Ireland
- McEvoy, Caitríona M., Tallaght University Hospital, Dublin, Leinster, Ireland
- Jayawardene, Satish, St James's Hospital, Dublin, Leinster, Ireland
Introduction
Multiple Myeloma (MM), ANCA-associated vasculitis and Anti-GBM diseases are recognised causes of acute kidney injury (AKI). Concurrent positivity for these conditions is exceptionally rare and may create a significant diagnostic uncertainty. We report a case of rapidly progressive AKI with positive serology for ANCA, Anti-GBM antibodies and MM
Case Description
A 73-year-old woman with osteoarthritis presented with fatigue and lethargy, following recent antibiotic treatment for presumed urinary tract infection. She reported a transient lower limb rash during antibiotic therapy. On admission, serum creatinine was 1.13 mg/dL and progressed to 6.50 mg/dL over following days. Laboratory investigations demonstrated eosinophilia. Urine dip showed protein 100mg/dl and trace blood.
Urgent acute screen revealed positive atypical ANCA, elevated proteinase-3 antibody titre 11 IU/ml (0.0-1.90), and anti-GBM antibodies titre of 27 U/ml (0.0-6.9), suggesting double-positive vasculitis. Further evaluation identified IgG paraproteinemia of 19G/l, markedly elevated free kappa light chains 2590.40 mg/l (3.3-19.4), and a kappa/lambda ratio of 149.39 (0.26-1.65). The patient commenced pulsed methylprednisolone and therapeutic plasma exchange. Further immunosuppressive therapy was deferred pending renal and bone marrow biopsies.
Bone marrow biopsy confirmed MM. Renal biopsy subsequently demonstrated cast nephropathy without crescentic glomerulonephritis, establishing MM as the primary cause of AKI.
The patient was then established on RVD chemotherapy. Her AKI recovered without requiring dialysis, with latest creatinine of 1.13 mg/dL.
Discussion
This case illustrates the diagnostic complexity in patients presenting with rapidly progressive AKI and multiple concurrent positive serological findings. While the combination of recent antibiotic, lower limb rash, eosinophilia and AKI suggested acute interstitial nephritis, the presence of positive ANCA with elevated PR3 and positive anti-GBM antibodies raised concern for double-positive renal vasculitis. The marked paraproteinemia raised suspicion for a concurrent plasma cell dyscrasia-related renal disease which may cause or co-exist with small-vessel vasculitis. This case highlights the importance of renal biopsy in establishing the dominant pathology of an AKI with multiple potential differential diagnoses