Disease in humans

Although much less publicized, Hyperkalemic Periodic Paralysis has also been observed in humans. In humans the disorder causes episodes of extreme muscle weakness, with attacks often beginning in infanthood. Depending on the type and severity of the HyperKPP, it can increase or stabilize until the fourth or fifth decade where attacks may cease, decline, or, depending on the type, continue on into old age. Factors that can trigger attacks include rest after exercise, potassium-rich foods, stress, fatigue, weather changes, certain pollutants (eg: Cigarette smoke) and periods of fasting. Muscle strength often improves between attacks, although many affected people may have increasing bouts of muscle weakness as the disorder progresses (abortive attacks). Sometimes with HyperKPP those affected may experience degrees of muscle stiffness and spasms (myotonia) in the affected muscles. This can be caused by the same things that trigger the paralysis, dependent on the type of myotonia. (See also paramyotonia).
Some people with Hyperkalemic Periodic Paralysis have increased levels of potassium in their blood (hyperkalemia) during attacks. In other cases, attacks are associated with normal blood potassium levels (normakalemia). Ingesting potassium can trigger attacks in affected individuals, even if blood potassium levels do not rise in response.