Genetic factors: genetic susceptibility risk (50, 55) (assessment of family history (16)), which can be extrapolated from the already established genetic correlation between MS and IBD, with genes such as IFNG (regulation of Th1 and Th2 cytokines), PTGER4 (via prostaglandin E, which regulates cytokines), CXCR6 (expressed in CD8+ T cells) or GPR25 being investigated by Yang et al. (55). The gene discussed is PTGER4; the disease is myeloid sarcoma.