Weight Loss With Topiramate and Phentermine Combination Therapy in a Patient With Bardet-Biedl Syndrome

There is limited data on the effect of antiobesity medications in individuals with Bardet-Biedl syndrome (BBS). Here, we present a case of an adult with BBS who experienced significant weight loss following treatment with a combination of topiramate and phentermine. A 31-year-old female with BBS, with homozygous pathogenic variant in the <i>BBS2</i> gene, presented with obesity, dyslipidemia, and obstructive sleep apnea. At 29 years of age, her body mass index (BMI) was 43.3 kg/m² (reference range 18.5-24.9 kg/m²), and she was initiated on 50 mg topiramate daily for migraine prophylaxis. With lifestyle modifications, BMI dropped to 40.5 kg/m². Subsequently, phentermine 30 mg daily was added. Eight months after adding phentermine, BMI significantly decreased to 31.5 kg/m² (27% decrease in BMI), with improvement in glycemic and lipid parameters. She developed paranoia due to a social stressor prompting a brief hold of phentermine and resumption at a lower dose. This case highlights the weight loss response with phentermine and topiramate combination therapy in a patient with BBS. Further research is needed to explore the efficacy and safety of conventional antiobesity medications in isolation, as sequential or combination therapy to setmelanotide, to most effectively impact weight and metabolic burden in patients with BBS.