Differences in IL-1RA between SG1 and SG2 echo a study that identified IL-1RA and IL-1β as significant discriminators in cytokine-based CRPS subgroups (Alexander et al. 2012). However, since IL-1β was not consistently detected in the patients from this study, a direct comparison between our subgroups and those in the previous study is not possible. The gene discussed is IL1B; the disease is complex regional pain syndrome.