[Periodic hypokalemic paralysis disclosing thyrotoxicosis]

Hypokaliemic periodic paralysis is an uncommon complication of hyperthyroidism occurring sporadically almost exclusively in young Asian men. The clinical presentation is the same as in familial hypokaliemic periodic paralysis. Treatment consists of conventional management for thyrotoxicosis.

A Laotian man aged 42 years had suffered episodes of pain and fatigue in the lower limbs lasting 2 to 7 days over the last few months. The patient was hospitalized with severe limb pain. Clinical examination found severe motor deficit involving all four limbs. Laboratory findings induced hypokaliemia (1.8 mmol/l) and hyperthyroidism (free thyroxin 36 pmol/l, TSH < 0.005 mlU/l). Thyroid echography revealed multinodular goitre with two heterogeneous nodules. Strong uptake was seen on the scintigram. The motor deficit regressed within 8 hours and the kaliemia was restored with 1.50 g KCl. The patient was discharged with carbimazole (30 mg/d). Three months later he was euthyroid and symptom free. Total thyroidectomy was performed and L-thyroxin prescribed. The patient remains symptom-free at the last follow-up, 5 months after thyroidectomy.

The pathogenesis of hypokaliemic periodic paralysis involves the ATPase-dependent sodium-potassium pump whose activity is stimulated by thyroid hormones. The reasons for the ethnic and male predominance are poorly elucidated.