Hypokalemic periodic paralysis: Difference between revisions

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. As a result, the muscle cannot contract efficiently (paralysis). The condition is hypokalemic (manifests when potassium is low; not "causing hypokalemia") because a low extracellular potassium ion concentration will cause the muscle to repolarise to the [[resting potential]] more quickly, so even if calcium conductance does occur it cannot be sustained. It becomes more difficult to reach the calcium threshold at which the muscle can contract, and even if this is reached then the muscle is more likely to relax. Because of this, the severity would be reduced if potassium ion concentrations are kept high.<ref>{{cite journal |vauthors=Rüdel R, Lehmann-Horn F, Ricker K, Küther G |title=Hypokalemic periodic paralysis: in vitro investigation of muscle fiber membrane parameters |journal=Muscle Nerve |volume=7 |issue=2 |pages=110–20 |date=February 1984 |pmid=6325904 |doi=10.1002/mus.880070205 }}</ref><ref>{{cite journal |vauthors=Jurkat-Rott K, Lehmann-Horn F |title=Muscle channelopathies and critical points in functional and genetic studies |journal=J. Clin. Invest. |volume=115 |issue=8 |pages=2000–9 |date=August 2005 |pmid=16075040 |pmc=1180551 |doi=10.1172/JCI25525 }}</ref><ref>{{cite journal|last=Kim|first=SJ|author2=Lee, YJ |author3=Kim, JB |title=Reduced expression and abnormal localization of the KATP channel subunit SUR2A in patients with familial hypokalemic periodic paralysis|journal=Biochemical and Biophysical Research Communications|date=January 2010|volume=391|issue=1|pages=974–8|doi=10.1016/j.bbrc.2009.11.177|pmid=19962959}}</ref>

 

 

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.