the myotonic disorders are a heterogeneous group of genetically determined diseases that are unified by the presence of myotonia, which is defined as failure of muscle relaxation after activation. the presentation of these disorders can range from asymptomatic electrical myotonia, as seen in some forms of myotonia congenita (mc), to severe disability with muscle weakness, cardiac conduction def...

Paramyotonia congenita is a non-progressive disease characterised by myotonia (failure of muscle relaxation) induced by the exposure of the affected muscles to cold. Episodes of flaccid paralysis occur and may be related to hyperkalaemic periodic paralysis. Proximal myopathy or muscular hypertrophy may occur. The condition is inherited as an autosomal dominant.' Severe paralysis may occur with ...

BACKGROUND Periodic paralyses and paramyotonia congenita are rare disorders causing disabling weakness and myotonia. Mutations in sodium, calcium, and potassium channels have been recognized as causing disease. OBJECTIVE To analyze the clinical phenotype of patients with and without discernible genotype and to identify other mutations in ion channel genes associated with disease. METHODS Th...

The presence of myotonia and paramyotonia on clinical examination and of myotonic discharges during electrodiagnostic (EDX) studies are important for the diagnosis of certain neuromuscular conditions. The increased muscle activity of myotonia produces muscle stiffness that improves with repeated activity. Paramyotonia produces a similar symptom, but the stiffness paradoxically increases with ac...

Familial hyperkalemic periodic paralysis is an autosomal-dominant channelopathy characterized by reversible paralysis associated with episodic hyperkalemia. Mutations in the skeletal muscle voltage-gated sodium channel gene (SCN4A) have been reported to be responsible for this disorder. Paramyotonia congenita is also caused by mutations in the SCN4A gene. Here, we report the case of a 17-year-o...

Paramyotonia congenita was first described by Eulenberg (1886). It is a rare, hereditary disorder of muscle in which severe loss of power is induced by degrees of cooling which are insufficient to affect normal muscle. Myotonia also appears on cooling. However, the paralysis produced by cooling distinguishes paramyotonia from Thomsen's disease. The weakness and myotonia can easily be produced u...

The authors describe an Italian kindred with nine individuals affected by hyperkalaemic periodic paralysis associated with paramyotonia congenita (hyperPP/PMC). Periodic paralysis was particularly severe, with several episodes a day lasting for hours. The onset of episodes was unusually early, beginning in the first year of life and persisting into adult life. The paralytic episodes were refrac...

Mutations of skeletal muscle sodium channel a subunit (SCN4A) gene are associated with a group of allelic diseases, including periodic paralysis, paramyotonia congenital, sodium channel myotonia, and congenital myasthenic syndrome. Periodic paralysis is characterized by episodic attacks of flaccid weakness with the fluctuation of serum potassium, which are usually limited to skeletal muscles ow...

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