MC4R and obesity due to melanocortin 4 receptor deficiency: This observation aligns with previous research showing that the expressivity of obesity in individuals with loss-of-function MC4R variants tends to increase over generations, affecting grandparents, parents, and children with growing severity [19]. Unfortunately, in the present study historical BMI data from childhood or adulthood were not available for the affected family members other than the index patient, limiting the ability to compare growth trajectories and further investigate this trend.