A case of microscopic polyangiitis with interstitial pneumonia after coronavirus disease-2019 infection, evidenced by positivity for multiple autoantibodies.

Anti-neutrophil cytoplasmic antibody-associated vasculitis is triggered by infection, dust exposure, and drugs. A 73-year-old male presented with dyspnea. Severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) infection was confirmed upon admission. Exacerbation of interstitial pneumonia and renal dysfunction were observed. Analysis revealed positivity for myeloperoxidase-anti-neutrophil cytoplasmic antibody, other anti-aminoacyl transfer RNA synthetase antibodies, and anti-melanoma differentiation-associated gene 5. Renal biopsy confirmed crescentic glomerulonephritis, leading to the diagnosis of microscopic polyangiitis. Combination therapy with prednisolone and cyclophosphamide was initiated, resulting in improved respiratory and renal failure. There is a potential association between SARS-CoV-2 infection and the onset of autoimmune diseases.