Kidney Week

Abstract: FR-PO0769

A Not-So-Pauci-Immune Case of Myeloperoxidase (MPO)-ANCA Rapidly Progressive Glomerulonephritis with Atypical Immunoglobulin Deposits and Hypocomplementemia

Session Information

• Glomerular Diseases: ANCA Vasculitis, Anti-GBM Disease, and Crescentic GN
  October 23, 2026 | Location: Exhibit Hall A, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Glomerular Diseases

• 1402 Glomerular Diseases: Clinical, Outcomes, and Therapeutics

Authors

• Tipo, Jerricho, The University of Texas Medical Branch John Sealy School of Medicine, Galveston, Texas, United States

Jerricho Tipo

• Akbar, Zain J., The University of Texas Medical Branch John Sealy School of Medicine, Galveston, Texas, United States

Zain J. Akbar

• Yakubu, Aliu Opeyemi, The University of Texas Medical Branch at Galveston, Galveston, Texas, United States

Aliu Opeyemi Yakubu, MD

• Shenawi, Ibrahim S., The University of Texas Medical Branch at Galveston, Galveston, Texas, United States

Ibrahim S. Shenawi, MD, MBA

• Dabech, Abdulaziz, The University of Texas Medical Branch at Galveston, Galveston, Texas, United States

Abdulaziz Dabech, MD

• Wong, Mike, The University of Texas Medical Branch at Galveston, Galveston, Texas, United States

Mike Wong, MD

• Hassan, Syed F., The University of Texas Medical Branch at Galveston, Galveston, Texas, United States

Syed F. Hassan, MD

• Hussein, Hussein A., The University of Texas Medical Branch at Galveston, Galveston, Texas, United States

Hussein A. Hussein, MD, MBChB

Introduction

MPO-ANCA-associated vasculitis is characterized by necrotizing small vessel inflammation commonly affecting the kidneys and lungs. Renal involvement classically manifests as crescentic glomerulonephritis with minimal immune complex deposition and leads to pauci-immune rapidly progressive glomerulonephritis (RPGN). Differentiation of pauci-immune RPGN from anti-GBM and immune complex-mediated forms is essential due to management and prognostic differences with diagnosis primarily made by kidney biopsy and supported by serologies. Yet, rare cases describing concurrent immune complex deposits on ANCA-associated vasculitis challenges this traditional paradigm. We report a case of newly diagnosed MPO-ANCA-associated RPGN confounded by immunoglobulin deposits on biopsy.

Case Description

A 70-year-old male presented with three months of weakness, fatigue, and anorexia. Vital signs were normal. Physical exam notable for cachexia and bilateral upper lobe lung crackles. Labs revealed BUN of 187 mg/dL and creatinine 10.4 mg/dL (0.95 mg/dL two months prior) and he was admitted for AKI. RPGN was suspected after urine studies showed hematuria (19 RBC/hpf) and proteinuria (urine protein creatinine ratio, 1.4 g). Serologies demonstrated high titer MPO Ab IgG of 152 AU/mL and p-ANCA IFA 1:1280, negative PR3-ANCA, anti-GBM and ANA, and low C3 (70 mg/dL) and C4 (19 mg/dL). CRP and ESR were elevated. He was stabilized with hemodialysis and corticosteroids. Kidney biopsy showed 65% cellular and fibrocellular crescents and 20% interstitial fibrosis and tubal atrophy. Notably, immunofluorescence demonstrated mild mesangial and capillary wall staining for IgG, IgM, C3, kappa and lambda and electron microscopy showed subepithelial hump-like electron dense deposits. He was treated with pulse-dose corticosteroids, rituximab (1,000 mg ×2 doses administered two weeks apart per RA protocol), followed by steroid taper and initiation of avacopan. He was discharged as dialysis dependent AKI with rheumatology follow up.

Discussion

RPGN is a nephrologic emergency that presents as glomerulonephritis with extremely rapid decline in renal function. Although diagnosis by kidney biopsy is gold-standard, here we show how overlapping pathology may obscure classification and we emphasize the importance of integrating clinical and serologic evidence to correctly identify and initiate appropriate treatment to optimize outcomes.