MC4R and obesity due to melanocortin 4 receptor deficiency: Of note, in an unpublished study from another center in our city, frequency of MC4R mutations was reported to be 8.6% among 93 obese children and adolescents (mean age 7.3±3.7 years) who started to gain weight before 6 years of age and had a history of early-onset obesity in a first-degree relative (16).