Incidental Omental Necrotizing Vasculitis Leading to the Diagnosis of Pediatric Antineutrophil Cytoplasmic Antibody-Associated Vasculitis

Introduction: Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a rare autoimmune disorder characterized by necrotizing inflammation of small to medium-sized vessels, often with renal involvement. Pediatric AAV, with an incidence below 10 cases per 1,000,000 children per year, often presents subtly, manifesting with nonspecific symptoms such as fatigue, pallor, and mild edema, leading to diagnostic delays and significant morbidity. Case Description: A previously healthy 5-year-old girl presented with severe acute kidney injury (creatinine 9.91 mg/dL), hyperkalemia (7.9 mEq/L), anemia (hemoglobin 6.8 g/dL), and oliguria, necessitating emergent dialysis. Routine histological examination of omental tissue obtained during dialysis catheter placement unexpectedly revealed prominent and widespread necrotizing vasculitis. This critical finding prompted further autoimmune evaluation, yielding highly positive MPO-ANCA serology. Renal biopsy subsequently confirmed advanced pauci-immune glomerulonephritis with extensive chronicity and rare remnant crescents. Although the kidneys showed end stage disease on biopsy, immunosuppression was initiated to prevent vasculitic injury to other organ systems. The patient was started on methylprednisone 30mg/kg IV q24 hrs for 3 days and then transitioned to prednisolone 2mg/kg/day. She also began rituximab 300mg IV weekly for 4 doses. She was discharged home on 30mg prednisolone that was eventually tapered. The patient eventually received a living related kidney transplant. Discussion: This case highlights the diagnostic importance of histopathological examination of routine surgical specimens. In this case, incidental necrotizing vasculitis was discovered on omental tissue that was submitted from dialysis catheter placement. This finding prompted further workup that lead to the diagnosis of AAV.