Case report of PLXNA4 variant associated with hyper-response to phentermine/topiramate pharmacotherapy: Potential genetic basis for superior weight loss response?

Background: Once thought to be primarily a result of lifestyle, it is now known that obesity has significant genetic components. Dozens of genes have been linked to obesity, and office-based genetic testing for obesity-associated genes is now readily available. As both pharmacotherapy and genetic testing for obesity become more accessible, pharmacogenetic personalization is becoming a reality. In this case report, a patient with a PLXNA4 polymorphism had a superior weight loss response to phentermine/topiramate therapy than has previously been reported in the literature. Thus, variants in PLXNA4 may provide a genetic basis for this patient's superior response to weight loss pharmacotherapy and cardiovascular risk factor reduction. Methods: In this case study, office-based genetic testing was utilized to identify the presence of variants in nearly 80 genes that have been linked to obesity in a patient who had hyper-responsive weight loss results on phentermine/topiramate pharmacotherapy. Results: A variant of the PLXNA4 gene, which has known pathogenic variants linked to genetic obesity syndromes, was identified in this patient who had a superior weight loss response to phentermine/topiramate pharmacotherapy. Conclusion: Due to overlapping molecular pathways, it is possible that PLXNA4 variants convey a superior weight-loss response and therefore superior cardiovascular risk factor reduction phentermine/topiramate therapy. Further studies are needed to examine the relationship between PLXNA4 variants and weight loss with phentermine/topiramate pharmacotherapy.