Paramyotonia Congenita (PMC), also known as Eulenburg Disease, is a rare, hereditary mineral metabolic disorder, which is also called a channelopathy and it affects the muscles used in movement. Caused by certain triggers, the sodium channels close much too slowly and the sodium, potassium, chloride and water continue to flow into the muscles. The skeletal muscles can become stiff, tight, tense or contracted and weak. PMC is caused by mutations in the SCN4A gene, a voltage-gated sodium channel. There is a 100% penetrance. This means if one has one of the mutations for it, they have a 100% chance of having it. In the same family, some members may have mild forms and others may have more extreme cases. It is actually considered to be a form of Hyperkalemic Periodic Paralysis, however, the symptoms can appear from shifting of potassium into low or high ranges or even if potassium shifts within normal levels. Symptoms can begin shortly after birth or during childhood or at anytime in early adulthood.
Myotonia is the prolonged or lengthy contraction, tensing or lack of relaxation of a muscle or group of skeletal muscles, which is relieved by exercise. For those with Paramyotonia Congenita, the contractions or tightness are not relieved by exercise. The symptoms or muscle tightness are brought on by triggers such as exercise or exertion, repeated movement and cold. It is also known that episodes are common in the early morning so sleeping in, in the morning, may cause episodes. Hands, face and eyelids are often seen affected. It can be seen as simply a hand cramp while writing or the inability to let go of something being held in the hand like a door knob or the affects can be as significant as total body paralysis with contracted and tight muscles. The episodes can last for minutes, hours or days. There may also be intermittent flaccid paralysis as in the other types of Periodic Paralysis in which there is no muscle tone and the muscles are totally loose and slack. Because breathing muscles may be affected, shortness of breath may accompany episodes. Episodes may be mild or very severe and pain may be experienced even after the episode has ended. Individuals with PMC may appear to be stiff or look tense, even when not in an episode.
“General anaesthesia may trigger episodes of paralysis lasting for hours, in individuals with hyperkalemic periodic paralysis or paramyotonia congenita. For this reason, depolarizing muscle relaxants and acetylcholinesterase inhibitors are particularly unsuitable. In order to avoid complications the anaesthetist must be informed about the disorder in advance of surgery.”
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