Background: Pathogenic PTEN gene mutations are known to cause PTEN tumor hamartoma syndrome. Recent studies also suggest a role for PTEN mutations in the pathogenesis of obesity. No PTEN mutations have been reported among bariatric surgery patients and obesity treatment results are unknown. Since preventive screening for associated tumors is offered to patients with molecular proven PTEN hamartoma tumor syndrome, recognition of this condition in the bariatric surgery clinic is important. Method: We present a patient with morbid obesity who carries a known pathogenic PTEN mutation, identified at the bariatric surgery clinic using an obesity gene panel consisting of 52 obesity–associated genes. We analyzed the weight loss response during the first 3 years after Sleeve Gastrectomy. Results: At 1, 2 and 3 years after surgery, the patient achieved a Total Body Weight Loss of 39.4%, 48.8% and 44.9%, respectively. This corresponds to the results of a control group of 18 female patients with normal genetic test results. Conclusion: Our patient illustrates the importance of recognizing this serious genetic condition for which preventive cancer screening options are available. The positive weight loss results after Sleeve Gastrectomy suggest that this could be a successful treatment option for obesity patients with PTEN mutations.