Muscle channelopathies

Skeletal muscle channelopathies are a heterogeneous group of rare neuromuscular disorders caused by mutations in muscle ion channel genes. They include non-dystrophic myotonia and periodic paralysis. Molecular defects have been disclosed in CLCN1, SCN4A, CACNA1S and KCNJ2 genes, encoding for chloride, sodium, calcium and potassium muscle channels, respectively. Non-dystrophic myotonia are characterized by myotonia, muscle stiffness, pain and weakness. The periodic paralyses are characterized by episodes of flaccid paralysis.

 

NON-DYSTROPHIC MYOTONIA:
–       MYOTONIA CONGENITA:
Thomsen myotonia (autosomal dominant)
Becker myotonia (autosomal recessive)
–       SODIUM CHANNEL MYOTONIA (autosomal dominant)
–       PARAMYOTONIA CONGENITA (autosomal dominant)

 

PERIODIC PARALYSIS:

–       HYPOKALIEMIC PERIODIC PARALYSIS (autosomal dominant)
–       HYPERKALIEMIC PERIODIC PARALYSIS (autosomal dominant)
–       ANDERSEN-TAWIL SYNDROME (autosomal dominant)

Muscle channelopaties show a wide spectrum of overlapping phenotypes making the diagnosis a challenge. The phenotype can differ for the same mutation even in the same family. Genetic analysis is important to define which gene is involved especially in hypokaliemic periodic paralysis type I and type II that are almost indistinguishable.

 

– Ulzi G, Lecchi M, Sansone V, Redaelli E, Corti E, Saccomanno D, Pagliarani S,  Corti S, Magri F, Raimondi M, D’Angelo G, Modoni A, Bresolin N, Meola G, Wanke E, Comi GP, Lucchiari S. Myotonia congenita: novel mutations in CLCN1 gene and functional characterizations in Italian patients. J Neurol Sci. 2012;318(1-2):65-71.

– Modoni A, Bianchi ML, Vitulano N, Pagliarani S, Perna F, Sanna T, Rizzo V, Silvestri G. Lack of Any Cardiac Involvement in a Patient with Andersen-Tawil Syndrome Associated with the c.574A→G Mutation in KCNJ2. Cardiology. 2011;120(4):200-3.

– Modoni A, D’Amico A, Dallapiccola B, Mereu ML, Merlini L, Pagliarani S, Pisaneschi E, Silvestri G, Torrente I, Valente EM, Lo Monaco M. Low-rate repetitive nerve stimulation protocol in an Italian cohort of patients affected by recessive myotonia congenita. J Clin Neurophysiol. 2011 Feb;28(1):39-44.

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