A rare case of IgG4-associated disease caused by COVID-19: Case report and literature review.

An increasing number of cases have reported that coronavirus disease 2019 (COVID-19) can lead to immune system dysregulation and induce autoimmune diseases, but the mechanism is unclear. We treated a patient who presented with an unknown fever after infection with the novel coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in 2023. After excluding the possibility of infection, malignancy, and other connective tissue diseases, we considered the diagnosis of IgG4-related disease in consideration of the patient's pathology and clinical findings.