Pathogenic SCN5A Mutation and Thyrotoxicosis-Related Neurological Syndrome: Casual or Causal Relationship?

Background: Various neurologic complications of hyperthyroidism are reported, and most these reversible with the amelioration thyrotoxicosis. We report a previously undescribed concurrence hyperthyroid-associated exercise-induced myalgia stiffness, pyramidal tract dysfunction, myoclonic movements that make an initial clinical diagnosis difficult. Case presentation: A 17-year-old male was hospitalized in department neurology, presenting 4-year history severe weakness lower limbs, movements. Laboratory investigations unexpectedly revealed hyperthyroidism. MRI brain spine, electrophysiology, whole exome sequencing were also performed. Antithyroid therapy led to marked improvement symptoms, accompanied by significant time-dependent decline compound muscle action potentials (CMAP) amplitudes after exercise normalization prolonged QTc interval. Genetic analysis identified rare variant SCN5A. Conclusion: This case provides important insights into relationship between neurologic/cardiac complications, particularly those genetic predisposition. SCN5A mutation possibly plays role complex neurological syndrome associated Further studies warranted better understand underlying mechanisms potential therapeutic options for conditions.