A 54 year old Caucasian male presented with progressive muscle weakness leading to complete paralysis in upper and lower limbs evident on examination. Initial venous gas analysis showed potassium of 2.1 mmol/l, and ECG showed U waves with prolonged QTc. A diagnosis of hypokalaemic periodic paralysis was made, and intravenous potassium administered. The paralysis gradually resolved over the next 34 h, as repeat serum potassium level rose to 4.0 mmol/l. He described 6 month history of episodic weakness happening almost daily after exercise, and resolved spontaneously with rest. He exercised strenuously as a professional body builder and consumed unusually high calorific and high glycemic index foods. Further assessment revealed a history of tremor, weight loss, sweating, and family history of thyroid disease. He had tremors and lid lag. Biochemistry confirmed Graves thyrotoxicosis with fT4 of 58 pmol/l, suppressed TSH, and elevated TRAb 19.3 U/l. He was advised on low carbohydrate and low glycemic index diet, and commenced on propranolol and carbimazole. He noticed instant improvement in weakness, and had no further paralysis for a week in hospital.
Thyrotoxic periodic paralysis (TPP) is most commonly seen in Asian men. Although familial hypokalaemic periodic paralysis can be seen in Caucasians, TPP, as in this case, is exeptionally rare in Caucasian men. TPP is a complex disorder, leading to muscle paralysis through variety of mechanisms. Treatment with antithyroid drugs, beta blockers and dietary modifications can lead to immediate relief of symptoms. Intravenous potassium in acute setting is essential to prevent potentially life threatening cardiac arrythmias. Raising physician awareness about early detection of thyrotoxicosis in all patients of periodic paralysis may improve patient outcomes. This case also demonstrates that unusually high carbohydrate diet can often precipitate paralysis, and physicians should consider patients dietary habits in establishing diagnosis and formulating management plan.
07 Nov 2016 - 09 Nov 2016