Burden of hyperphagia and obesity in Bardet-Biedl syndrome: a multicountry survey

Clinically Meaningful Outcomes after 1 Year of Treatment with Setmelanotide in an Adult Patient with a Variant in SH2B1

INTRODUCTION

Monogenic obesity is caused by a unique genetic dysfunction, often appears in childhood, and can be accompanied by neuroendocrine, skeletal, developmental, and behavioral disorders, among other manifestations. Some variants in the SH2B1 gene have been suggested as strong candidates for the development of autosomal dominant obesity.

CASE PRESENTATION

We describe here the clinical response after 1 year of setmelanotide treatment in a 22-year-old patient with an SH2B1 variant. After 3 months of treatment, our patient lost 5.4% of body weight. This period was followed by a 3-month period of noncompliance, in which the patient gained 4% body weight. After reinstating daily drug administration, the patient showed a 19.5% reduction in body weight and a clear improvement in all hunger scales after 1 year of treatment.

CONCLUSION

These results indicate that the changes seen are drug dependent and provide positive evidence for the administration of setmelanotide in adult patients with heterozygous variants in the SH2B1 gene.

Bardet-Biedl syndrome: A focus on genetics, mechanisms and metabolic dysfunction

Bardet-Biedl syndrome (BBS) is a rare, monogenic, multisystem disorder characterized by retinal dystrophy, renal abnormalities, polydactyly, learning disabilities, as well as metabolic dysfunction, including obesity and an increased risk of type 2 diabetes. It is a primary ciliopathy, and causative mutations in more than 25 different genes have been described. Multiple cellular mechanisms contribute to the development of the metabolic phenotype associated with BBS, including hyperphagia as a consequence of altered hypothalamic appetite signalling as well as alterations in adipocyte biology promoting adipocyte proliferation and adipogenesis. Within this review, we describe in detail the metabolic phenotype associated with BBS and discuss the mechanisms that drive its evolution. In addition, we review current approaches to the metabolic management of patients with BBS, including the use of weight loss medications and bariatric surgery. Finally, we evaluate the potential of targeting hypothalamic appetite signalling to limit hyperphagia and induce clinically significant weight loss.