Genetic predisposition to obesity in bulimia nervosa: a mutation screen of the melanocortin-4 receptor gene.

Obesity has been identified as a risk factor for the development of bulimia nervosa (BN). Accordingly, we hypothesize that genotypes predisposing to obesity can be detected in patients with this eating disorder. In order to investigate this hypothesis we screened the melanocortin-4 receptor gene (MC4R) for mutations using single strand conformation analysis in 81 female inpatients treated for BN. A single patient with both extreme obesity and BN had a haplo-insufficiency mutation in the MC4R. Comparison of current and maximal body mass index (BMI) of all patients with cross-sectionally obtained BMI in the general population revealed an age appropriate distribution for current BMI and a substantially increased frequency for overweight at time of maximal BMI. Our findings suggest that overweight is a risk factor for BN in clinically ascertained patients. For the first time a genotype predisposing to obesity has been detected in an extremely obese patient with BN.