With regards to IL-10 and IL-6 (the cytokines that distinguished PF from RF), there were significant differences in the levels of IL-6 and IL-10 between the four groups (ANOVA, p < 0.001 and p = 0.002, respectively), but PF patients were not different from RF patients, even if the CFS-like phenotype was established at this time. Here, IL10 is linked to myalgic encephalomeyelitis/chronic fatigue syndrome.