This study examined the polymorphic variants of genes known to be involved in miRNA biogenesis (DROSHA rs10719, XPO5 rs11077, RAN rs14035, AGO1 rs636832, DICER1 rs3742330, GEMIN3 rs197412, GEMIN4 rs7813, HIWI rs1106042) in patients with MS and in a control group. The gene discussed is RAN; the disease is myeloid sarcoma.