LEP and obesity due to melanocortin 4 receptor deficiency: In contrast, the rare cases of monogenic forms of obesity, are mainly caused by biallelic mutations in a single gene, usually in the leptin-melanocortin satiety pathway, and are characterized by vary severe, early-onset obesity, usually with evident hyperphagia, and in some cases associated to other metabolic comorbidities and influencing growth pattern even in the first years of life (Handakas et al., 2022).