Proteinase 3-Antineutrophil Cytoplasmic Antibody (PR3-ANCA)-Associated Vasculitis: A Case Report

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a group of rare, heterogeneous, and potentially life-threatening diseases, typically characterized by their phenotype (microscopic polyangiitis, granulomatosis with polyangiitis, or eosinophilic granulomatosis with polyangiitis) but currently classified according to the type of antibody that is identified: proteinase 3 (PR3), myeloperoxidase (MPO), or negative. A 55-year-old man presented with a two-week history of fever, myalgias, and odynophagia, and two days of pleuritic pain, cough, hemoptysis, and purpuric lesions on both inferior limbs. CT scan documented multiple lung nodules surrounded by ground-glass opacities, and laboratory tests showed increased erythrocyte sedimentation rate, acute kidney injury, microscopic hematuria, and non-nephrotic proteinuria. Additional tests revealed PR3-ANCA positivity. Diffuse alveolar hemorrhage was confirmed, and a kidney biopsy unveiled pauci-immune focal crescentic glomerulonephritis. After two weeks of glucocorticoids, he initiated rituximab, with a gradual, promising response. Effective treatment is vital in chronic inflammatory diseases, such as AAV, with an impact on both organ damage and global prognosis, which is why this diagnosis should be considered in the presence of suspected clinical signs or symptoms, to achieve better therapeutic results.