Case: A 35 year old Hispanic male presents to the Emergency Department for acute onset weakness, particularly in the bilateral upper and lower extremities. Symptoms started abruptly last night after a stressful work day. He denies any recent illnesses, insect bites, or rashes. Vitals are within normal limits. On exam, there is pronounced weakness in his proximal muscles with his lower extremities slightly weaker than his upper extremities. His grip strength is preserved. Reflexes are normal.
Differential diagnosis includes: thyrotoxic periodic paralysis, hypokalemic periodic paralysis, myasthenic crisis, Guillain-Barre syndrome, transverse myelitis, tick paralysis
Case continued: Labs are notable for a potassium 1.7, magnesium 1.5, TSH < 0.01, Free T4 5.9, Free T3 23.5. EKG showing sinus rhythm with prolonged QTc. Management included IV and PO repletion of potassium which improved the patient’s symptoms rapidly. He was also started on methimazole for hyperthyroidism. Finally, he was admitted to a telemetry monitored bed to check serial BMPs and monitor for rebound hyperkalemia.
Teaching Pearls:
- Thyrotoxic periodic paralysis is a form of acquired hypokalemic periodic paralysis, often precipitated by rest after strenuous exercise or high carbohydrate load.
- Treat with potassium repletion, continuous cardiac monitoring, and monitor potassium levels for rebound hyperkalemia.
- For acute weakness episodes not responsive to potassium replacement, use Propranolol.
- Treat hyperthyroidism – attacks should cease with euthyroid state.
References:
Chaudhry MA, Wayangankar S. Thryotoxic Periodic Paralysis: A concise review of the literature. Curr Rheumatol Rev. 2016;12(3):190-194.
Kung AW. Clinical review: Thyrotoxic periodic paralysis: a diagnostic challenge. J Clin Endocrinol Metab. 2006 Jul;91(7):2490-5. Epub 2006 Apr 11.
Vijayaumar A, Ashwath G, Thimmappa D. Thyrotoxic periodic paralysis: clinical challenges. J Thyroid Res 2014;2014:649502
