Given that genetic factorsmay affect MS, we have studied geneticvariation in HLA and cytokine genes, and haveanalyzed expression of genes encoding TNFrelatedapoptosis inducing Ligand (TRAIL)and matrix metalloproteinase-9 (MMP9) inIranian patients with MS previously (14-18).Genes encoding VDR and CYP24A1, as a keyenzyme in vitamin D metabolism, are reportedto be involved in MS in certain countries (19,20). Here, TNFSF10 is linked to myeloid sarcoma.