It is estimated that monogenic diseases with Mendelian inheritance represent approximately 5% of non-syndromic cases of obesity, including mutations in the leptin receptor and BDNF, MC4R, MC3R, PCSK1, PCSK2, POMC, PPARG, SIM1, and TRKB genes, among others. The gene discussed is MC4R; the disease is obesity due to melanocortin 4 receptor deficiency.