Human herpesvirus-8 (HHV-8)-negative/idiopathic multicentric Castleman disease (iMCD) is a rare, hematologic disorder involving multiple enlarged lymph nodes with characteristic histopathology, cytopenias, and systemic inflammation due to a cytokine storm often including interleukin-6 (IL-6) (1–3). Here, IL6 is linked to idiopathic multicentric Castleman disease.