Thyrotoxic periodic paralysis complicated by acute hypercapnic respiratory failure and ventricular tachycardia

Background: Thyrotoxic hypokalemic periodic paralysis in combination with an acute episode of general flaccid paralysis and hypokalemia is common in young Asian men with hyperthyroidism. We report the very rare complications of involvement of the respiratory muscles and ventricular tachycardia in this disorder. Summary: A 29-year-old man exhibited profound paralysis after prolonged fasting. Severe hypokalemia was noted (K⁺: 1.4 mmol/L). Although the patient was treated with potassium chloride, he suffered from respiratory distress and chest tightness. Arterial blood gas indicated acute hypercapnic respiratory failure (pCO₂: 118.9 mmHg), and ventricular tachycardia was documented by electrocardiogram. The patient was intubated for ventilatory support and treated with intravenous potassium, after which paralysis gradually resolved. Thyroid function tests showed elevated free thyroxine and low thyroid-stimulating hormone concentrations, even though the patient did not have goiter or typical symptoms of thyrotoxicosis. Conclusion: Thyrotoxic periodic paralysis usually involves the proximal muscles of the limbs, but on rare occasions it can affect the respiratory muscles with the potential for severe and even fatal complications.