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. The gene discussed is ARG1; the disease is in situ carcinoma.