Hypokalemic periodic paralysis (HPP) is a rare autosomal dominant disorder characterised by episodic muscle weakness associated with hypokalemia. Hypolemic paralysis can also occur due to other causes including renal tubular acidosis (RTA). We describe 2 cases of hypokalemic paralysis of different aetiologies.
Case:1: A 23 year polish man who speaks no English was admitted with profound weakness in his limbs. Laboratory investigations revealed normal renal function with profound hypokalemia (potassium 1.9 mmol/L). Arterial blood gases, serum bicarbonate, thyroid functions, serum aldosterone and plasma renin activity levels were normal. The patient was started on potassium chloride and triamterene and he recovered over a period of 24 hrs. Subsequent history from his brother revealed that he had 4 similar episodes in the past explaining the periodic nature.
Case:2: An eighteen old white male was admitted with profound muscle weakness. He had previous kidney transplants for posterior urethral valves. Investigations revealed a profound hypokalemia (1.9 mmol/L), mild renal failure, metabolic acidosis and alkaline urine consistent with hypokalemic paralysis secondary to RTA. He regained full muscle power with the correction of hypokalemia. He was transferred to renal unit for further management.
Discussion: The first attack of HPP usually occurs around puberty and each attack may last for upto 48 hrs. In between attacks, the patients are usually strong with normal potassium levels. Mutation in the CACNL1A3 account for majority of cases. Acetozolamide, triamterene or spirinolactone are some of the treatment options.
The non-inherited forms can be secondary to various conditions including thyrotoxicosis, primary hyperaldosteronism, liquorice ingestion and RTA. Although the clinical manifestation is similar in both the cases, the long term management for the two types of hypokalemic paralysis is different and therefore a clear understanding about this condition is essential. Failure to make a distinction between these two types may result in mismanagement.