ANCA-Positive Polyarteritis Nodosa

Introduction: Polyarteritis Nodosa (PAN) is a systemic necrotizing vasculitis primarily affecting medium-sized arteries. Kidney involvement usually manifests as microaneurysms of renal arteries, leading to tissue hemorrhage and infarction. PAN typically does not cause glomerulonephritis. Here we present a unique case of rapidly progressive glomerulonephritis (GN) from PAN. Case Description: A 77-year-old female with history of hypertension was admitted for sudden onset diplopia and ataxia. She had been feeling ill for the last 3 months with symptoms including malaise, cough, diarrhea, and generalized weakness, but denied skin rash, joint pain or swelling. She was found to have oliguric acute kidney injury with serum Cr 3.9mg/dL from a baseline of 0.53mg/dL just 2 months ago. Urinalysis showed 1+ heme with 30mg/dL of protein. Spot urine protein to creatinine ratio was 1.23mg/dL. Hepatitis panel was negative. Pertinent serologies included positive c-ANCA with a titer of 1:80, anti-myeloperoxidase (MPO) antibodies 1.0 AI (Antibody Index). Renal biopsy revealed small to medium vasculitis, pauci-immune focal necrotizing crescentic GN with extensive cortical necrosis and interstitial hemorrhage, along with severe interstitial fibrosis and tubular atrophy (IFTA). Computed tomography angiogram was done to rule out ANCA vs PAN, which showed several microaneurysms within the mesenteric vessels and spleen. She was thus diagnosed with extra-renal, severe PAN. Unfortunately, she required hemodialysis due to poor urine output and persistent hyperkalemia. An immunosuppressive (IS) regimen was initiated despite severe IFTA due to patient’s request which included oral cyclophosphamide and high dose prednisone after intravenous pulses. Thus far, two months after her hospitalization, she remains on dialysis and the IS medications were tapered off. Discussion: Although rare, PAN can lead to pauci-immune RPGN and lead to severe kidney dysfunction. Microaneurysms in the kidneys should prompt high suspicion for this disease entity.