Painful cramps and giant myotonic discharges in a family with the Nav1.4‐G1306A mutation

ABSTRACT Introduction: Two previously reported Norwegian patients with painful muscle cramps and giant myotonic discharges were genotyped and compared with those of members of 21 families harboring the same mutation. Methods: Using primers specific for SCN4A and CLCN1, the DNA of the Norwegian famil...

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Bibliographic Details
Published in:Muscle & nerve 2015-10, Vol.52 (4), p.680-683
Main Authors: Torbergsen, Torberg, Jurkat‐Rott, Karin, StÅLberg, Erik V., Løseth, Sissel, Hødneø, Anne, Lehmann‐Horn, Frank
Format: Article
Language:English
Subjects:
Adult
Electromyography
ephaptic transmission
Evoked Potentials, Motor - genetics
Family Health
Female
G1306A
Humans
Middle Aged
Muscle Cramp - complications
Muscle Cramp - genetics
muscle pain
mutation
Mutation - genetics
myotonia
NAV1.4 Voltage-Gated Sodium Channel - genetics
positive waves
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Summary:ABSTRACT Introduction: Two previously reported Norwegian patients with painful muscle cramps and giant myotonic discharges were genotyped and compared with those of members of 21 families harboring the same mutation. Methods: Using primers specific for SCN4A and CLCN1, the DNA of the Norwegian family members was amplified and bidirectionally sequenced. Clinical and neurophysiological features of other families harboring the same mutation were studied. Results: A G1306A mutation in the Nav1.4 voltage‐gated sodium channel of skeletal muscle was identified. This mutation is known to cause myotonia fluctuans. No giant myotonic discharges or painful muscle cramps were found in the other G1306A families. Conclusions: Ephaptic transmission between neighboring muscle fibers may not only cause the unusual size of the myotonic discharges in this family, but also a more severe type of potassium‐aggravated myotonia than myotonia fluctuans. Muscle Nerve 52: 680–683, 2015
ISSN:0148-639X
1097-4598
1097-4598
DOI:10.1002/mus.24672