Semaglutide reverses the chronic myopathy of hyperkalemic periodic paralysis: a case report.

BACKGROUND: Hyperkalemic Periodic Paralysis (hyperPP) is an autosomal dominant genetic disorder where high extracellular potassium is associated with skeletal muscle depolarization and both flaccid muscle weakness as well as delayed muscle relaxation that can lead to myotonia and myopathy. Interventions have typically relied on avoidance of triggers, low potassium diets, and diuretics like acetazolamide and diclofenamide with limited success. CASE PRESENTATION: The patient is a 48 year old man with hyperPP from a familial autosomal dominant sodium channel point mutation in the SCN4A gene at position 704 with a Threonine to Methionine substitution that lead to symptoms starting in early childhood. By age 30 he developed permanent muscle weakness and neither acetazolamide nor diclofenamide as interventions had improved his myopathy. In the spring of 2023, semaglutide was initiated for weight loss. Before the semaglutide he could not rise out of a chair without help and his gait was very slow. Over the next year his strength and quality of life returned to levels he had not had in decades. CONCLUSION: This is a promising alternative treatment for hyperPP. By directly acting on skeletal muscle both dependent and independent of insulin, Semaglutide and likely other Glucagon-like peptide agonists show promise as a novel once weekly option that may treat not just the hyperkalemic periodic paralysis but also the skeletal muscle atrophy in a multimodal way.