IL6 and immunoglobulin G4-related sclerosing disease: Furthermore, overexpression of IL-6 and a cytokine storm is an important clinical finding of both MCD and TAFRO syndrome related to systemic symptoms, but other diseases such as hemophagocytic syndrome, IgG4-related disease, various infections or autoimmune diseases, or even after chimeric antigen receptor T-cell therapy also frequently occurs, making IL-6 elevation unsuitable for differential diagnosis (39).