We report a 4-generation Turkish family with 10 affected members presenting with myotonia and potassium- and exercise-induced paralytic attacks. The clinical presentation was neither typical for the chloride channel myotonias Thomsen and Becker nor for the separate sodium channel myotonia entities potassium-aggravated myotonia, paramyotonia congenita, and hyperkalemic periodic paralysis. It is ...

Paramyotonia congenita, the major characteristics of which are cold-induced and exercise-induced myotonia, is an autosomal-dominant muscle disease which is classified into one of a group of muscle diseases, so-called muscle "sodium channelopathies" caused by missense mutations in the gene coding for the skeletal muscle sodium channel a-subunit (SCN4A) (1-4). Such muscle sodium channelopathies s...

Background: Muscle channelopathies such as paramyotonia, hyperkalemic periodic paralysis, and potassiumaggravated myotonia are caused by gain-of-function Na channel mutations. Methods: Implementation of a threedimensional radial Na magnetic resonance (MR) sequence with ultra-short echo times allowed the authors to quantify changes in the total muscular Na signal intensity. By this technique and...

BACKGROUND Over the past 3 years, the genetics of the myotonic diseases have been substantially elaborated. Three genetically different groups of myotonic disease can be discerned: (1) the chloride channel myotonias, (2) the adynamia-paramyotonia complex, and (3) myotonic dystrophy. METHODS AND RESULTS Electrophysiology has suggested and molecular biology has proven that the diseases belongin...

Myotonia is a failure of voluntary muscle to relax immediately innervation ceases. The clinical and electrical manifestations reflect a primary abnormality of the muscle cell membrane. Myotonia is commonly observed in three syndromes. (1) Myotonia congenita (Thomsen, 1876), is an inherited condition, transmitted by a dominant gene. The myotonia affects all muscles which are often hypertrophied....

Hereditary muscle channelopathies are caused by dominant mutations in the genes encoding for subunits of muscle voltage-gated ion channels. Point mutations on the human skeletal muscle Na+ channel (Nav1.4) give rise to hyperkalemic periodic paralysis, potassium aggravated myotonia, paramyotonia congenita and hypokalemic periodic paralysis type 2. Point mutations on the human skeletal muscle Ca2...

Hyperkalaemic periodic paralysis, paramyotonia congenita, and potassium-aggravated myotonia are three autosomal dominant skeletal muscle disorders linked to the SCN4A gene encoding the alpha-subunit of the human voltage-sensitive sodium channel. To date, approximately 20 point mutations causing these disorders have been described. We have identified a new point mutation, in the SCN4A gene, in a...

Hyperkalemic periodic paralysis (hyperPP) is characterized by attacks of flaccid limb weakness (which may also include weakness of the muscles of the eyes, throat, and trunk), hyperkalemia (serum potassium concentration >5 mmol/L) or an increase of serum potassium concentration of at least 1.5 mmol/L during an attack of weakness and/or provoking/worsening of an attack by oral potassium intake, ...