Rare Case of Renal Limited Dual Anti-Neutrophil Cytoplasmic Antibody-Associated Vasculitis: Double Trouble!

Abstract

Dual anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV) characterized by the presence of both anti-proteinase-3 (PR3-ANCA) and anti-myeloperoxidase (MPO-ANCA) antibodies is a rare clinical entity. Only few cases have been reported previously, most of which were associated with infections, drugs, autoimmune diseases and malignancies. Herein, we describe a young woman who presented with rapidly progressive glomerulonephritis with hypocomplementemia and markedly elevated anti-PR3 and anti-MPO titres. Meticulous work-up ruled out all possible secondary causes. Renal biopsy showed the presence of focal fibrocellular crescents with focal mesangial hypercellularity. Immunofluorescence and electron microscopy showed pauci-immune deposits. The patient was treated with an induction regimen comprising oral prednisolone and cyclophosphamide. She attained both clinical and serological remission at 3 months and is currently on an azathioprine-based maintenance regimen. We have extensively reviewed all previous cases of dual AAV and have formulated an approach to diagnose and treat this rare entity.

Keywords

• anca-associated vasculitis
• anti-proteinase-3
• anti-myeloperoxidase
• hypocomplementemia
• crescents