Hypokalaemia periodic paralysis.

Hypokalaemic periodic paralysis is a rare skeletal muscle channelopathy causing flaccid paralysis, which predominantly presents in adolescents and young adults. I report a case of a 33-year-old Caucasian man who presented with sudden onset paralysis, following previous similar presentations without investigation. Blood tests revealed undetectable serum potassium levels in the context of paralysis. Other causes of hypokalaemia were excluded, and the patient was treated with planned lifelong prophylactic potassium replacement for a diagnosis of primary hypokalaemic periodic paralysis. This case demonstrates that, although rare, hypokalaemic periodic paralysis should be considered as a differential diagnosis in young patients who present with sudden flaccid paralysis and can easily be excluded by checking serum potassium levels at presentation.