In individuals with this mutation, attacks sometimes begin in adolescence and most commonly occur with individual triggers such as rest after strenuous exercise (attacks during exercise are rare), high carbohydrate meals, meals with high sodium content, sudden changes in temperature, and even excitement, noise, flashing lights, cold temperatures and stress.
[2] Hypokalemic periodic paralysis is a condition that causes episodes of extreme muscle weakness typically beginning in childhood or adolescence.
[3] Mutations in the following genes can cause hypokalemic periodic paralysis: An association with KCNE3 (voltage-gated potassium channel) has also been described, but is currently disputed,[4] and excluded from the disease definition in OMIM.
This depolarisation propagates to the T-tubules where it triggers the entry of calcium ions via Cav1.1 as well as from the sarcoplasmic reticulum through the associated ryanodine receptor RyR1.
[citation needed] In patients with mutations in SCN4A or CACNA1S, therefore, the channel has a reduced excitability and signals from the central nervous system are unable to depolarise the muscle.
[citation needed] In contrast, hyperkalemic periodic paralysis refers to gain-of-function mutations in sodium channels that maintain muscle depolarisation and therefore are aggravated by high potassium ion concentrations.
[citation needed] This condition is inherited in an autosomal dominant pattern (but with a high proportion of sporadic cases), which means one copy of the altered gene in each cell is sufficient to cause the disorder.
[citation needed] Factors known to trigger episodes are: stress, cold environment or hypothermia, carbohydrate load, infection, glucose infusion, metabolic alkalosis, alcohol, strenuous exercise, and steroids.
The tendency of people with hypokalemic periodic paralysis to get paralyzed when epinephrine is released in "fight or flight" situations further adds to the temptation to misdiagnose the disorder as psychiatric.
Avoiding carbohydrate-rich meals, strenuous exercise and other identified triggers, and taking acetazolamide or another carbonic anhydrase inhibitor, may help prevent attacks of weakness.
Abortive attacks often respond to extra potassium, cutting carbohydrates, getting plenty of rest, increasing doses of medication and gentle daily exercise such as short walks.
[citation needed] Life span is expected to be normal,[12] but attacks can drop potassium to levels low enough to cause life-threatening breathing problems or heart arrhythmia.
Migraines occur in up to 50% of all hypokalemic periodic paralysis patients and may include less common symptoms like phantom smells, sensitivity to light and sound or loss of words.
[citation needed] In 1935 the Scottish physician Dr Mary Walker was the first to recognise the association between familial periodical paralysis and hypokalaemia.
She also described the glucose challenge test used in diagnosing hypokalaemic periodic paralysis and the use of intravenous potassium in its treatment.