Association of COVID-19 antigenicity with the development of antineutrophilic cytoplasmic antibody vasculitis

Inflammatory processes, such as an infection or drug reaction, can cause antineutrophil cytoplasmic autoantibody (ANCA)-associated vasculitis (AAV). Although quite rare, AAV may occur with SARS-coronavirus disease 2019 (COVID-19) antigenic exposure, either from infection or immunization. We present two cases of AAV: one that developed after COVID-19 infection presenting as diffuse alveolar haemorrhage and another that developed shortly after vaccination, presenting as granulomatous pulmonary nodules. Both patients improved with supportive care and immunosuppressive therapies. This adverse event appears to be a very rare complication of COVID-19 infection or vaccination. Early diagnosis of AAV is important because immunosuppressive therapy may improve patient outcomes.