PRTN3 and neutropenia: Although the mechanism for tocilizumab‐induced neutropenia is not firmly established, it may occur rapidly within few hours, indicating limited involvement of bone marrow.26 In patients with rheumatoid arthritis, the neutropenia induced by tocilizumab has been attributed to the inhibition of antiapoptotic actions of IL‐6 on activated neutrophils,27 and evidence for a proapoptotic effect of tocilizumab treatment has been demonstrated in vitro.28 Thus, the rapid increase in PRTN3 could be related to its release from apoptotic neutrophils.