Mutations in the human skeletal muscle Na+ channel underlie the autosomal dominant disease hyperkalemic periodic paralysis (HPP). Muscle fibers from affected individuals exhibit sustained Na+ currents thought to depolarize the sarcolemma and thus inactivate normal Na+ channels. We expressed human wild-type or M1592V mutant α-subunits with the β1-subunit in Xenopus laevis oocytes and recorded Na...

Familial hypokalemic periodic paralysis (HOPP) is a rare autosomal-dominant disease characterized by reversible attacks of muscle weakness occurring with episodic hypokalemia. Mutations in the skeletal muscle calcium (CACNA1S) and sodium channel (SCN4A) genes have been reported to be responsible for familial HOPP. Fifty-one HOPP patients from 20 Korean families were studied to determine the rel...

Todd paralysis (TP) is a relatively rare postictal phenomenon characteristic with weakness of the limbs in various degrees, following epileptic seizures. Since it is a reversible phenomenon in general, the reported duration of TP varies between half-an-hour to 36 hours. However, there is limited data in the literature about TP which persists more than 36 hours. On this aspect, we presented this...

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...

Periodic paralysis, cardiac arrhythmia and bone features are the hallmark of Andersen's syndrome (AS), a rare disorder caused by mutations in the KCNJ2 gene that encodes for the inward rectifier K(+)-channel Kir2.1. Rest following strenuous physical activity, carbohydrate ingestion, emotional stress and exposure to cold are the precipitating triggers. Most of the mutations act in a dominant-neg...

Over 60 mutations of SCN4A encoding the NaV1.4 sodium channel of skeletal muscle have been identified in patients with myotonia, periodic paralysis, myasthenia, or congenital myopathy. Most mutations are missense with gain-of-function defects that cause susceptibility to myotonia or periodic paralysis. Loss-of-function from enhanced inactivation or null alleles is rare and has been associated w...

An increasing number of human diseases have been found to result from mutations in ion channels, including voltage-gated cation channels. Though the mutations are known, the pathophysiological mechanisms underlying many of these channelopathies remain unclear. In this issue of the Journal, Struyk and Cannon (see p. 11) provide evidence for a novel mechanism, proton movement catalyzed by the vol...

OBJECTIVES To determine the possible prognostic indicators of unilateral vocal fold paralysis (UVFP) and survey the timing and values of preset laryngeal electromyography (LEMG) rules for UVFP. DESIGN Cohort study with retrospective data analysis. SETTING Voice clinic of a tertiary medical center. PATIENTS Complete data for 45 patients diagnosed with idiopathic or iatrogenic UVFP. The LEM...