So far, 16 genes have been identified for monogenic obesity, including leptin (LEP), leptin receptor (LEPR), pro-opiomelanocortin (POMC), prohormone convertase subtilisin/kexin type 1 (PCSK1), melanocortin receptor type 3 (MC3R) and type 4 (MC4R), Melanocortin Receptor Accessory Protein 2 (MRAP2), and adenylate cyclase 3 (ADCY3) [189,190,191,192,193]. The gene discussed is MRAP2; the disease is obesity due to melanocortin 4 receptor deficiency.