Myotonia fluctuans
K. Ricker, F. Lehmann-Horn and R. T. Moxley 3rd
Department of Neurology, University of Wurzburg, West Germany.
Autosomal-dominantly inherited nondystrophic myotonic disorders are an
interesting group of muscle diseases that provide considerable opportunity
for future molecular genetic studies to identify the genes responsible for
specific membrane functions. A family with such a myotonic disorder is
described with features that are distinctly different from myotonia
congenita and paramyotonia congenita. Five members were affected in three
generations. The myotonia fluctuated to an unusual degree. It did not
worsen with cold but increased markedly with potassium loading. Muscle
weakness never occurred. Analysis of the contraction force of the flexor
digitorum muscle showed a unique type of myotonia, namely, exercise-induced
delayed-onset myotonia. Microelectrode studies done on one muscle biopsy
specimen revealed a normal chloride conductance of the muscle fiber
membrane.
What causes paramyotonia in the United Kingdom?: Common and new SCN4A mutations revealed
Matthews et al.
Neurology 2008;70:50-53.
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A novel founder SCN4A mutation causes painful cold-induced myotonia in French-Canadians
Rossignol et al.
Neurology 2007;69:1937-1941.
ABSTRACT
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Muscle Na+ channelopathies: MRI detects intracellular 23Na accumulation during episodic weakness
Weber et al.
Neurology 2006;67:1151-1158.
ABSTRACT
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Voltage-Gated Ion Channels and Hereditary Disease
Lehmann-Horn and Jurkat-Rott
Physiol. Rev. 1999;79:1317-1372.
ABSTRACT
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Familial cramp due to potassium-aggravated myotonia
Orrell et al.
J. Neurol. Neurosurg. Psychiatry 1998;65:569-572.
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Myotonic Disorders in Childhood: Diagnosis and Treatment
Moxley
J Child Neurol 1997;12:116-129.
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Genetics and Physiology of the Myotonic Muscle Disorders
Ptacek et al.
NEJM 1993;328:482-489.
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The skeletal muscle chloride channel in dominant and recessive human myotonia
Koch et al.
Science 1992;257:797-800.
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