Thyrotoxic periodic paralysis

Abstract

A 39 -year-old male, with primary hyperthyroidism for the last-3 years, for which he was not receiving any treatment, presented with complaints of sudden onset weakness in all four limbs for one day. Weakness was more in the lower limbs; and was not associated with sweating or related to a carbohydrate-rich diet. Family history, drug- history was unremarkable. On physical examination, he was anxious; exophthalmos was evident. Resting pulse rate was 112/min; rest of the general physical examination was normal. Systemic examination revealed complete absence of movement in lower limbs power 0/5 [Medical research Council (MRC) grading], but he was able to move his upper limbs against gravity 3/5 (MRC grading). Deep tendon reflexes were absent. Rest of the neurological and other systems examination were unremarkable. Laboratory testing showed hypokalemia (serum potassium 2.6 mEq/L); thyroid profile revealed TSH 0.01 mIU/L, T3 2.0ng/ml, free T4 3.3 ng/mL. A possible diagnosis of thyrotoxic periodic paralysis was considered; he was treated with intravenous correction of potassium and was started on carbimazole and propranolol. On the next 48 hours, power in all the limbs became normal and deep tendon reflexes were normally elicitable. He was asymptomatic by the third day and was discharged in a stable condition with advice to follow-up in Medicine out-patient department. Thyrotoxic paralysis is a benign condition if it is diagnosed early and treated promptly. Though it is a rare condition, it requires special mention because of its life-threatening complications. The diagnosis at initial presentation is often delayed because of the subtleness of clinical features of thyrotoxicosis.

Keywords

• hyperthyroidism
• hypokalaemia
• periodic paralysis