Leptin is a peptide hormone which regulates food intake, energy expenditure and metabolism.3 It also acts on the immune system cells by influencing the production of cytokines.1, 2 It has been previously observed that in RRMS (relapsing remitting multiple sclerosis) patients, leptin causes the production of cytokines by peripheral blood mononuclear cells (PBMC) in the acute phase of the disease and these changes in leptin serum levels are related to disease activity.1, 4–6. The gene discussed is LEP; the disease is relapsing-remitting multiple sclerosis.