IL6 and Castleman disease: The efficacy, excellent tolerability, and safety of tocilizumab have been verified in numerous clinical trials resulting in the approval of this biologic for the treatment of RA (Tanaka et al, 2014), juvenile idiopathic arthritis (Yokota et al, 2008, 2012), and Castleman's disease (Nishimoto et al, 2008), the latter being a non‐cancerous disorder of the lymph nodes characterized by non‐clonal hyperproliferation of B cells resulting from IL‐6 hypersecretion.