There are 30 different types of periodic paralysis but the most common include hypokalemic periodic paralysis (HypoKPP), hyperkalemic periodic paralysis (HyperKPP), and Andersen-Tawil Syndrome. Other forms of the disease include thryotoxic HypoKPP, normokalemic, and paramyotonia congenita, among many others. Periodic paralysis is a disorder that results in sporadic muscle weakness or paralysis, often as a reaction to potassium levels. Depending on the type, attacks can last for moments or days. The disorder is usually passed on genetically, and symptoms can first emerge anywhere from birth to well into a person’s old age.
Many types of periodic paralysis are classified by how they interact with potassium. For instance, the symptoms of HypoKPP occur when blood potassium levels drop. Usually, this occurs after a person has eaten carbohydrate-laden foods or during rigorous exercise, and usually disappears once the patient has ingested some potassium. In contrast, those with HyperKPP are more sensitive to potassium and thus may experience more severe effects. Sufferers of this form of the disease may experience paralysis or weakness when blood potassium levels increase.
A form of HypoKPP, thyrotoxic HypoKPP, is marked by an overactive thyroid gland, and is most common among Asian males. Sufferers of thyrotoxic HypoKPP may also experience swallowing or breathing problems, changes in vision, and trouble speaking, in addition to paralysis and muscle weakness. There is also a form of HyperKPP called normokalemic periodic paralysis that occurs even when potassium levels remain stable.
Paramyotonia congenital is a form of the disease that is marked by paralysis and weakness in response to potassium, low temperatures, or exercise. With paramyotonia congenital, if a person tries to continue activity while experiencing symptoms, the stiffness can get worse. This form of the disease can manifest by itself, but is more commonly accompanied by HyperKPP or, less frequently, HypoKPP.
One type of periodic paralysis not included in conventional classifications is Andersen-Tawil syndrome. This form of the disease defies such classification because potassium levels can rise or fall during attacks. In addition to the muscle weakness or paralysis, a person with this disease may also have different physical attributes. For instance, a person may have webbed toes, low-set ears, or wide-set eyes. The physical occurrences do not always occur with the disease, and a person in the same family may carry the physical traits without having symptoms of the disease.