FTO and obesity due to melanocortin 4 receptor deficiency: The current study aimed to explore the potential association between the FTO rs17817449 gene polymorphism and obesity-related markers, and to evaluate the ability of this polymorphism in the prediction of overweight/obesity in DS children and adolescents. This case-control study included 100 DS children under the age of 18, classified into three groups according to BMI-percentile; 50 non-obese DS (NODS), 24 overweight DS, and 26 ODS.