SUN-LB88 Thyrotoxic Periodic Paralysis in Hispanic Patients

BACKGROUND: Thyrotoxic periodic paralysis (TPP) presents as acute intermittent attacks of weakness related to hypokalemia, commonly reported in Asians and rare in Hispanics(1). Patients with TPP will have triiodothyronine (T3) triggered increased Na+/K+ ATPase pump activity and transcription of the KCNJ18 gene that encodes for the Kir2.6 channel(2). This permits insulin, catecholamines, stress and alcohol(3) to increase cellular intake of potassium, which causes depolarization and leads to weakness and paralysis. We report a case of TPP in a young Hispanic man who presented with lower extremity weakness and falls. CASE PRESENTATION: A 34-year-old Hispanic man with Graves’ disease, non-adherent to medications presented with generalized weakness, more pronounced in legs, and recurrent falls. Physical examination was unremarkable except for mild enlargement of thyroid gland and abnormal gait due to weakness. Laboratory data showed hypokalemia of 1.8 mmol/L (3.7-5.1 mmol/L) and a TSH level of <0.004 mIU/L (0.34-5.6 mIU/L). Free T4 3.74 ng/dL (0.6-1.6 ng/dL), free T3 597 pg/dL (230-420 Pg/dL), thyroid stimulating Ig 148 (<130). Electrocardiogram did not show U waves. Radio iodine 123 scan of thyroid revealed diffusely increased 24-hour radioactive uptake of 66.5% (10-30%). The patient was diagnosed with TPP and supplemented with three doses of potassium 40 mEq IV infusion. Methimazole and metoprolol were started. He made a good clinical recovery within days. After discharge, he was treated with I-131 (13 mci) and developed postablative hypothyroidism on long term. He was euthyroid on levothyroxine. He did not have any recurrence of weakness at 7-year follow-up. CONCLUSION: TPP is uncommonly seen in Hispanics patients as opposed to Asians(3). Physicians should consider TPP as part of the differential diagnosis in young hyperthyroid Hispanic men presenting with weakness or paralysis, as early recognition and treatment can reduce recovery time and potentially prevent tachyarrhythmia or death. REFERENCES: 1. Matta A, Koppala J, Gossman W. Thyrotoxic hypokalaemic periodic paralysis: a rare presentation of Graves’ disease in a Hispanic patient. BMJ Case Rep. 2014;2014. 2. Ryan DP, Ptacek LJ. Mutations in Potassium Channel Kir2.6 Cause Susceptibility to Thyrotoxic Hypokalemic Periodic Paralysis. Cell, 140(1), pp.88-98. 3. Amblee, A. and Gulati, S. (2016). Thyrotoxic Periodic Paralysis: Eight Cases in Males of Hispanic Origin from a Single Hospital. AACE Clinical Case Reports, 2(1), pp.e58-e64.