ABSTRACT
We herein report a case of severe coronavirus disease 2019 (COVID-19) in which high-dose intravenous immunoglobulin (IVIg) treatment achieved significant clinical improvement of deterioration of pulmonary inflammation after temporary clinical improvement. In the present case, clinical and radiological deterioration occurred despite a decrease in viral load, suggesting that deterioration was caused by reactivation of proinflammatory factors, such as tumor necrosis factor-α and interleukin-6, rather than direct viral effects. IVIg treatment may provide not only immunosuppressive effects but also inhibition of proinflammatory cytokines, indicating that treatment including IVIg may be effective by inhibiting cytokine storm in severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infection.