BACKGROUND A common form of congenital myotonia, myotonia congenita (MC), is caused by mutations in the skeletal muscle Cl(-) channel gene type 1 (CLCN1). Due to the reduced Cl(-) conductance of the mutated channels, the patients may develop generalized muscle rigidity and hypermetabolism during general anaesthesia. The clinical symptoms resemble malignant hyperthermia (MH), which may lead to m...

Here we present the case of a 32-year-old female patient with myotonia congenita. She carried two mutations in the CLCN1 gene that encodes the chloride channel ClC-1: p.Phe167Leu, which was previously identified in several families, and p.Val536Leu, which has been previously reported but not yet characterized by electrophysiological investigations. The patient's symptoms included generalized st...

Chloride channels are involved in a multitude of physiologic processes ranging from basal cellular functions such as cell volume regulation and acidification of intracellular vesicles to more specialized mechanisms such as vectorial transepithelial transport and regulation of cellular excitability. This plethora of functions is accomplished by numerous functionally highly diverse chloride chann...

The cause of weakness was investigated in a patient with adynamia episodica hereditaria without myotonia. A pattern of exercise and rest produced episodes of hyperkalemic periodic paralysis. In addition, local muscle weakness was induced by forearm cooling. Investigations on isolated intercostal muscle demonstrated that a high potassium concentration in the bathing solution triggered a noninact...

Myotonia congenita (MC) is caused by loss-of-function mutations of the muscle ClC-1 chloride channel. Clinical manifestations include the variable association of myotonia and transitory weakness. We recently described a cohort of recessive MC patients showing, at a low rate repetitive nerves stimulation protocol, different values of compound muscle action potential (CMAP) transitory depression,...

BACKGROUND AND PURPOSE While the etiology and clinical features of "EMG disease" - which is characterized by diffusely increased insertional activity on needle electromyography (EMG) in the absence of neuromuscular disease - are not well known, some authorities believe it may be a form of myotonia congenita (MC). The aims of this study were to determine the clinical features of EMG disease and ...

Laryngospasm is a rare but potentially life-threatening occurrence in infants and usually has infective, allergic, metabolic, or anatomic causes. Underlying genetic conditions are rarely considered. Mutations in SCN4A encoding the voltage-gated sodium channel NaV1.4 have been implicated in a wide spectrum of neuromuscular disorders with variable onset, ranging from a rare form of congenital mya...

OBJECTIVE To electrophysiologically characterize the Na(v)1.4 mutant N440K found in a Korean family with a syndrome combining symptoms of paramyotonia congenita, hyperkalemic periodic paralysis, and potassium-aggravated myotonia. METHODS We characterized transiently expressed wild-type and mutant Na(v)1.4 using whole-cell voltage-clamp analysis. RESULTS N440K produced a significant depolari...