So far, several genes, such as proopiomelanocortin (POMC), leptin receptor (LEPR), leptin (LEP), proconvertase 1 (PC1), and melanocortin 4 receptor (MC4R), have been confirmed as the casual genes to the onset of monogenic obesity [3–10]. The gene discussed is LEP; the disease is obesity due to melanocortin 4 receptor deficiency.