Five-year outcome of bariatric surgery in a patient with melanocortin-4 receptor mutation.

Monogenic obesity is characterized by mutations in genes involved in the central regulation of food intake. Melanocortin-4 receptor (MC4R) mutations are the most frequent monogenic cause of severe early onset human obesity. Although bariatric surgery is the most effective therapy for idiopathic morbid obesity in adults, little is known about its effectiveness in patients with monogenic obesity syndromes. We report 5-year outcome of gastric bypass surgery in a young man with severe super-obesity associated with MC4R mutation. A 22-year-old man with a weight of 221.6 kg and body mass index of 76.7 kg m(-2) associated with a heterozygous MC4R mutation was referred to our centre for bariatric surgery. He underwent Roux-en-Y gastric bypass (RYGB) surgery and achieved weight loss of 76% of excess weight over a follow-up period of 58 months. Heterozygous MC4R mutations have been associated with dominantly inherited obesity in various ethnic groups, and non-surgical interventions are rarely effective in the long term. One previous report of bariatric surgery in a patient with complete MC4R deficiency reported poor weight loss after gastric banding. We speculate that patients with MC4R mutations achieve superior weight loss outcomes from procedures such as RYGB that produce neurohormonal changes rather than gastric restriction alone due to beneficial effects on appetite and satiety regulation.