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Myotonia congenita is a congenital neuromuscular channelopathy that affects skeletal muscles (muscles used for movement). It is a genetic disorder . The hallmark of the disease is the failure of initiated contraction to terminate, often referred to as delayed relaxation of the muscles ( myotonia ) and rigidity . [ 1 ]
The prevalence of DM1 ranges from 5 to 20 per 100,000 (1:20,000–1:5000). [5] Up to 48 per 100,000 (1:2100) individuals tested positive for the mutation of DM1 in New York, although not all of these individuals would have become symptomatic. [33] Again in New York, premutations for DM1 were found in 191 per 100,000 (1:525). [33]
Congenital fiber type disproportion affects skeletal muscle, typically causing weakness in the shoulders, upper arms, thighs, and hips. Skeletal muscle is made up of two kinds of fiber, type 1 and type 2. In congenital fiber type disproportion, type 1 fibers are not only smaller but often more abundant than type 2 fibers. [12]
Mutations in this gene cause two forms of inherited human muscle disorders: recessive generalized myotonia congenita (Becker) and dominant myotonia (Thomsen). [5] Chloride channel protein, skeletal muscle (CLCN1) is a protein that in humans is encoded by the CLCN1 gene. [6] Mutations in this protein cause congenital myotonia.
[1] [2] Myotonia is the defining symptom of many channelopathies (diseases of ion channel transport) such as myotonia congenita, paramyotonia congenita and myotonic dystrophy. [3] [4] Brody disease (a disease of ion pump transport) has symptoms similar to myotonia congenita, however, the delayed muscle relaxation is pseudo-myotonia as the EMG ...
NMT is a diverse disorder. As a result of muscular hyperactivity, patients may present with muscle cramps, stiffness, myotonia-like symptoms (slow relaxation), associated walking difficulties, hyperhidrosis (excessive sweating), myokymia (quivering of a muscle), fasciculations (muscle twitching), fatigue, exercise intolerance, myoclonic jerks and other related symptoms.
[1]: 396 [9] [10] The fainting was first described in scientific literature in 1904 and described as a "congenital myotonia" in 1939. [11] The mutation in the goat gene that causes this muscle stiffness was discovered in 1996, several years after the equivalent gene had been discovered in humans and mice. [11]
Paramyotonia congenita (PC) is a rare congenital autosomal dominant neuromuscular disorder characterized by "paradoxical" myotonia. [2] This type of myotonia has been termed paradoxical because it becomes worse with exercise whereas classical myotonia, as seen in myotonia congenita , is alleviated by exercise.