Homozygotes for the p.E42* MC4R mutation exhibited average BMI of 44.83 (44.83 ± 9.7 SD), indicative of extreme obesity (obesity class III) and significantly higher than the BMI of both heterozygous and wild type family members (p < 0.005). The gene discussed is MC4R; the disease is obesity due to melanocortin 4 receptor deficiency.