[A case of thyreotoxic hypokalaemic periodic paralysis in a white male]

Thyreotoxic hypokalaemic periodic paralysis (THPP) is a rare and potentially life-threatening syndrome. It principally affects men of East-Asian origin and has rarely been described in a white person.

A 34-year-old Dutch man, suffering from Graves' disease, presented with weakness in his lower limbs. Laboratory investigation showed severe hypokalaemia (1.8 mmol/l) and increased creatinine kinase levels. An electrocardiogram showed atrial fibrillation with a prolonged QTc-interval. The patient was admitted, cardiac rhythm was monitored, and he received potassium supplements. Laboratory investigation of thyroid function showed thyrotoxicosis. The patient was treated with propranolol and thiamazol. At follow-up, thyroid function, potassium levels and muscle strength had normalized.

Hypokalaemia due to thyrotoxicosis should be considered in cases of unexplained paralysis. The treatment of THPP consists of treating for hyperthyroidism plus propranolol. Since the hypokalaemia is self-limiting, potassium supplementation is only necessary in cases of rhythm disturbances or cardiac-conduction disturbances. Despite adequate treatment, there is a risk of recurrence. Regular monitoring is indicated until euthyroidism is achieved.