An unusual cause of muscle weakness: a diagnostic challenge.

We report a case of 24 year-old-female presenting with bilateral leg heaviness sensation and difficult walking of one-day duration. Over the past three months she developed progressive and frequent tingling sensation on her hands accompanied by headache and increased thirst. Hypokalemia was identified and treated with resolution of symptoms. She was later found to have Graves' disease. After propranolol and radioiodine therapy no further episodes were reported. Thyrotoxic hypokalemic periodic paralysis is an alarming, potentially lethal, and rare complication of hyperthyroidism. The pathogenesis is uncertain. Because the condition is rare, it is frequently overlooked and misdiagnosed on presentation. It is important to recognize these clinical settings in hypokalemic patients in order to promptly start adequate medical therapy and avoid the lethal complications caused by prolonged sustained potassium depletion.