ARG1 and myeloid sarcoma: This result supports higher ARG1 expression by PBMCs from those with MS and that the CIS patients studied were on a trajectory for conversion to MS (all CIS patients not receiving phototherapy converted to MS by 12 months of follow‐up).17 The increase after 3 months from baseline in ARG1 mRNA levels was not observed in the CIS patients that received phototherapy and suggested that the intervention may have stimulated pathways that stabilise ARG1 expression.