Periodic paralysis is a group of rare genetic diseases that lead to weakness or paralysis from common triggers such as cold, heat, high carbohydrate meals, not eating, stress or excitement and physical activity of any kind. The underlying mechanism of these diseases are malfunctions in the ion channels in skeletal muscle cell membranes that allow electrically charged ions to leak in or out of the muscle cell, causing the cell to depolarize and become unable to move.The symptoms of periodic paralysis can also be caused by hyperthyroidism, and are then labeled thyrotoxic periodic paralysis; however, if this is the underlying condition there are likely to be other characteristic manifestations, enabling a correct diagnosis. Types
Periodic paralysis is an autosomal dominant myopathy with considerable variation in penetrance, leading to a spectrum of familial phenotypes (only one parent needs to carry the gene mutation to affect the children, but not all family members who share the gene are affected to the same degree). Specific diseases include:
Hypokalemic periodic paralysis (Online Mendelian Inheritance in Man (OMIM): 170400), where potassium leaks into the muscle cells from the bloodstream. Hyperkalemic periodic paralysis (Online Mendelian Inheritance in Man (OMIM): 170500), where potassium leaks out of the cells into the bloodstream. Paramyotonia congenita (Online Mendelian Inheritance in Man (OMIM): 168300), a form which often accompanies hyperkalemic periodic paralysis, but may present alone. The primary symptom of paramyotonia congenita is muscle contracture which develops during exercise or activity. Paramyotonia congenita attacks may also be triggered by a low level of potassium in the bloodstream.
The old glucose/insulin provocative testing can cause life-threatening symptoms and should not be used.Also of note is that potassium levels do not have to range outside of normal limits to cause serious, even life-threatening paralysis. These diseases are not the same as having a very low level of potassium (hypokalemia) or high potassium (hyperkalemia) and must not be treated as such. The total body store of potassium is usually normal; it is just in the wrong place. Treatment
Treatment of the periodic paralyses may include carbonic anhydrase inhibitors (such as acetazolamide, methazolamide or dichlorphenamide), taking supplemental oral potassium chloride and a potassium-sparing diuretic (for hypos) or avoiding potassium (for hypers), thiazide diuretics to increase the amount of potassium excreted by the kidneys (for hypers), and significant lifestyle changes including tightly controlled levels of exercise or activity. However, treatment should be tailored to the particular type of periodic paralysis.Treatment of periodic paralysis in Andersen-Tawil syndrome is similar to that for other types. However, pacemaker insertion or an implantable cardioverter-defibrillator may be required to control cardiac symptoms. Prognosis
While the disability can range from minor, occasional weakness to permanent muscle damage, inability to hold a normal job and use of a powerchair, most people function fairly well with drugs and lifestyle changes. References
Song, YW; Kim, SJ; Heo, TH; Kim, MH; Kim, JB (Dec 2012). "Normokalemic periodic paralysis is not a distinct disease". Muscle & Nerve. 46 (6): 908–913. doi:10.1002/mus.23441. PMID 22926674. S2CID 43821573. External links
NIH information page on periodic paralysis