ESPE Abstracts (2016) 86 P-P2-943

Thyrotoxic Periodic Paralysis, an Under-Recognized Condition

Siu Ying Nip & Carolina Di Blasi

Seattle Children’s Hospital, University of Washington, Seattle, Washington, USA

Background: Thyrotoxic periodic paralysis (TPP) is a rare clinical manifestation of hyperthyroidism, commonly seen in Asian males. Patients often present with sudden onset muscle weakness associated with severe hypokalemia.

Case presentation: A 16-year-old Filipino male presented with acute onset bilateral lower extremities weakness. He woke up at night but was unable to move his legs. He denied any recent viral infections, ingestion of canned food or history of paralysis. He complained of occasional palpitation and more frequent bowel movement. He had a 2.5 kg weight loss despite increased appetite. He otherwise denied tremors, diaphoresis, mood lability or neck enlargement. Family history was non-contributory. On physical examination, he was afebrile, mildly tachycardic (pulse 120/min) with BP 133/66 mmHg. He had mild exophthalmos and subtle tremors. Thyroid gland was enlarged with audible bruits. He had bilateral lower extremity muscle weakness, 1/5 motor strength in proximal muscles with normal sensation. Reflexes were normal. Laboratory findings were significant for hypokalemia 2 mEq/L (3.5 – 5.5), hypomagnesemia 1.6 mg/dL (1.8 – 2.4), elevated creatine kinase 795 IU/L (39 – 308) but normal calcium level. ECG showed narrow complex sinus tachycardia and ST-T changes. He was managed with IV potassium and magnesium; Potassium normalized to 4.6 mEql/L and paralysis resolved upon discharge. Later tests revealed TSH <0.02 mcIU/ml (0.5 – 4.5), free T4 >7 ng/ml (0.8 – 2), total T3 >7.8 ng/mL (1 – 2.1). Anti-thyroid peroxidase and anti-thyroglobulin antibodies were positive and thyroid stimulating immunoglobulin index (TSI) was markedly elevated 6.6 (<1.3). He was diagnosed with Graves’ disease and started on Methimazole and Propranolol treatment.

Conclusion: Patients with TPP can have subtle signs and symptoms of thyrotoxicosis on presentation and is easily under-recognized. High index of suspicion is crucial in patients who present with acute paralysis associated with hypokalemia. Early diagnosis and treatment of the hyperthyroid state prevent life-threatening complications of hypokalemia and recurrence of paralysis.

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