Abstract: FR-PO0452
Rare Presentation of Concomitant Null-Null Membranoproliferative Glomerulonephritis (MPGN) and Acute Pyelonephritis in a Patient with Pulmonary Arterial Hypertension (PAH) and Chronic Osteomyelitis
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
- Shrestha, Rajesh, University of Maryland Medical Center, Baltimore, Maryland, United States
- Patel, AMi, University of Maryland Medical Center, Baltimore, Maryland, United States
Introduction
Drug-induced acute interstitial nephritis (DI-AIN) is a common presumption in patients developing Acute Kidney Injury (AKI) during prolonged antibiotic therapy. We present a case where kidney biopsy revealed an unexpected MPGN pattern with concomitant acute pyelonephritis, fundamentally altering the diagnosis and management.
Case Description
A 58-year-old woman with Chronic Kidney Disease (CKD) stage IIIb-A3, WHO group 1 PAH, monoclonal gammopathy of undetermined significance, and recurrent Pseudomonal thoracic spine osteomyelitis (s/p spinal fusion) presented with rapidly progressive AKI (creatinine 1.24 → 5.7 mg/dL over 3 weeks) during prolonged intravenous cefepime. Clinical suspicion favored DI-AIN given temporal correlation and prior cefepime-associated AKI. Cefepime was subsequently discontinued.
Kidney biopsy unexpectedly revealed concomitant findings of acute pyelonephritis with acute tubular injury and an MPGN pattern with mesangial expansion and thickened glomerular basement membranes. Direct immunofluorescence was negative (limited: single viable glomerulus). Electron microscopy demonstrated expanded endothelial spaces without immune deposits, fibrillary material, or tubuloreticular inclusions — consistent with endothelial injury. Urine cultures showed no growth. C3/C4, ANA, ANCA, HBV/HCV/HIV, and SPEP/UPEP with immunofixation were negative. Quantitative cryoglobulin was slightly positive. Prolonged course of cefepime may have selected for resistant organisms, and patient had notable improvement of her renal function after switching to levofloxacin.
The constellation of IF-negative MPGN, endothelial space expansion on EM supports infection-associated endothelial injury, potentially compounded by PAH-related endotheliopathy.
Discussion
This case illustrates that: (1) clinical anchoring on DI-AIN can delay recognition of acute bacterial pyelonephritis, particularly with subacute presentation like in our patients (2) IF-negative MPGN should prompt evaluation for endothelial injury rather than immune complex disease; and (3) PAH may serve as a predisposing factor for renal endothelial injury, with chronic infection providing an additional insult. The slightly positive cryoglobulin likely represents an epiphenomenon of chronic infection rather than primary pathology.