Case Report: Use of Plasma Exchange Followed by Convalescent Plasma Therapy in a Critically Ill Patient with Severe Fever and Thrombocytopenia Syndrome-Associated Encephalopathy: Cytokine/Chemokine Concentrations, Viral Loads, and Antibody Responses

We describe the case of a patient with severe fever with thrombocytopenia syndrome (SFTS) complicated by SFTS-associated encephalopathy who was successfully treated with 4-day plasma exchange followed by two-time convalescent plasma therapy. During plasma exchange, the plasma cytokines interferon-α and inducible protein-10 gradually decreased without change of plasma viral load. However, plasma viral load gradually decreased after convalescent plasma therapy. This case provides important insights for understanding the mechanisms of experimental therapy in severely affected SFTS patients.