Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8281342 | Journal of the Neurological Sciences | 2012 | 5 Pages |
Abstract
Mutations in the pore-forming subunit of the skeletal muscle sodium channel (SCN4A) are responsible for hyperkalemic periodic paralysis, paramyotonia congenita and sodium channel myotonia. These disorders are classified based on their cardinal symptoms, myotonia and/or paralysis. We report the case of a Japanese boy with a novel mutation of SCN4A, p.I693L, who exhibited severe episodic myotonia from infancy and later onset mild paralytic attack. He started to have apneic episodes with generalized hypertonia at age of 11Â months, then developed severe episodic myotonia since 2Â years of age. He presented characteristic generalized features which resembled Schwarz-Jampel syndrome. After 7Â years old, paralytic episodes occurred several times a year. The compound muscle action potential did not change during short and long exercise tests. Functional analysis of the mutant channel expressed in cultured cell revealed enhancement of the activation and disruption of the slow inactivation, which were consistent with myotonia and paralytic attack. The severe clinical features in his infancy may correspond to myotonia permanence, however, he subsequently experienced paralytic attacks. This case provides an example of the complexity and overlap of the clinical features of sodium channel myotonic disorders.
Related Topics
Life Sciences
Biochemistry, Genetics and Molecular Biology
Ageing
Authors
Harumi Yoshinaga, Shunichi Sakoda, Jean-Marc Good, Masanori P. Takahashi, Tomoya Kubota, Eri Arikawa-Hirasawa, Tomohiko Nakata, Kinji Ohno, Tetsuro Kitamura, Katsuhiro Kobayashi, Yoko Ohtsuka,