Antineutrophil cytoplasmic antibody-associated vasculitis predominantly manifesting tubulointerstitial nephritis: A case report

The Successful Treatment of Acute Kidney Injury Due to Antineutrophil Cytoplasmic Antibody (ANCA)-Associated Vasculitis Without Glomeruli Involvement by Using Rituximab: A Case Report

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) refers to a group of disorders characterized by inflammation and destruction of small- and medium-sized blood vessels. It can be classified into various clinical disease phenotypes: granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), eosinophilic granulomatosis with polyangiitis (EGPA), and renal-limited AAV or serologic subtypes, which are myeloperoxidase (MPO)-AAV and proteinase 3 (PR3)-AAV. Renal involvement is a common manifestation in these types of vasculitis. MPO-AAV usually involves the glomeruli causing membranous changes and presents with glomerulonephritis. However, MPO-AAV renal type without glomeruli involvement is much rarer, and very few case reports of this condition have been reported in the literature. Once the diagnosis is confirmed by renal biopsy, the treatment of AAV involves high-dose steroids and cyclophosphamide to induce remission. Rituximab, a chimeric monoclonal antibody that targets against the pan-B-cell marker CD20, was the first monoclonal antibody to be approved for the treatment of vasculitis. It is now considered first-line therapy for ANCA vasculitis with kidney involvement thanks to the higher remission rates associated with it. We report a unique and rare case of acute kidney injury due to MPO-AAV without glomeruli involvement, which was successfully treated with rituximab over a period of 12 months and led to the remission of the disease in the kidneys.