NPY and obesity due to melanocortin 4 receptor deficiency: Therefore, the gain encompassing only the NPY gene in patient Ob_12 and his obese mother, the point mutation in patient Ob_158 and her obese father while only 27 missense variants have been described among 118.884 alleles in ExAC are strong evidences supporting that gain of function mutations of NPY can cause severe obesity and ADHD.