AbstractThyroid storm is a life-threatening complication of hyperthyroidism that necessitates early diagnosis for aggressive, effective treatment. We present a patient with a newly diagnosed multinodular goiter who presented to the emergency department with leg swelling, dyspnea, tremors, and atrial fibrillation with elevation in thyroid hormone levels consistent with thyrotoxicosis. Despite improvement in peripheral hormone levels on maximized medical treatment with beta-blockers, methimazole, glucocorticoids, cholestyramine, and potassium iodide, she continued to clinically decline with new encephalopathy, heart failure, and liver and kidney dysfunction while receiving treatment. Work-up for alternative causes of her clinical decompensation was unrevealing. Plasmapheresis was initiated, with further reduction in thyroid hormone levels without clinical improvement. Cases in the literature do report incidences of severe thyrotoxicosis refractory to traditional treatment measures; however, generally, these cases involve a failure to reduce thyroid hormone levels with medical treatment and subsequent consideration of plasmapheresis. Our case suggests that clinical improvement in thyroid storm does lag behind biochemical improvement in select patients, and delayed clinical improvement or even severity of symptoms may warrant earlier consideration of plasmapheresis in such patients.