The clinical manifestations of idiopathic multicentric Castleman disease (iMCD) are thought to be caused by an excess of inflammatory cytokines; however, the mechanism is yet to be known. In addition to IL-6, inflammatory cytokines, such as IL-1β and TNF-α, are noted to be elevated in iMCD, which are common in autoinflammatory diseases. The first-line treatment for iMCD is an IL-6 inhibitor. Furthermore, increases in inflammatory cytokines such as serum IL-10 and IL-23, chemokines such as CXCL13 and CXCL-10 (especially in iMCD-TAFRO), and VEGF-A have been observed, and their relationship to pathogenesis has attracted the attention of researchers. The PI3K/Akt/mTOR pathway, JAK/STAT3 pathway, and type I IFN as drivers have recently been identified as important signals and are expected to be therapeutic targets in cases where IL-6 inhibitors are ineffective.