Periodic paralysis, hyperkalemic

Mutations of the NaVl. 4 channel gene cause various types of muscle diseases, including hyperkalemic periodic paralysis, paramyotonia congenita, myotonia fluctuans, acetazolamide-sensitive myotonia. Mutations disiupt inactivation and cause both myotonia (enhanced excitability) and attacks of paralysis (inexcitability resulting from depolarization). 

Hyperkalemic periodic paralysis AD 17q13 Sodium channel alpha subunit... 

Primary hyperkalemic periodic paralysis is usually first manifest in childhood. Attacks may last for a period of a few hours to several days, and the degree of muscle damage associated with the condition appears to increase with age and frequency of attacks. Vacuolation and dilatation of the SR is the most obvious form of damage, and it increases with age. 

Hyperkalemic periodic paralysis (MIM 170500) Sodium channel Skeletal muscle... 

Mutations of the sodium channel cause hyperkalemic periodic paralysis and paramyotonia congenital 720... 

Calcium-channel blockers are used for treating cardiac arrhythmia and pulmonary hypertension and for prevention of reperfusion injury. Sodium channels have been linked to epilepsy and hyperkalemic periodic paralysis (Table 8.1). 

SCN4A 17q23.1-25.3 Navi.4 Hyperkalemic periodic paralysis PC PAM D Gain... 

Mitrovic N, George AL Jr, Lerche H, Wagner S, Fahlke C, Lehmann-Horn F. Different effects on gating of three myotonia-causing mutations in the inactivation gate of the human muscle sodium channel. J Physiol. 1995 Aug 15 487 (Pt 1) 107-114. Lehmann-Horn F, laizzo PA, Halt H, Franke C. Altered gating and conductance of Na+ channels in hyperkalemic periodic paralysis. Pfliig. Arch. Fur. J. Phy. 1991 418 297-299. 

Cannon SC, Brown RH Jr, Corey DP. A sodium channel defect in hyperkalemic periodic paralysis potassium-induced failure of inactivation. Neuron 1991 6 619-626. 

Patients with muscle disorders (dystrophia myotonica, myotonia congenita, myasthenia gravis, and hyperkalemic periodic paralysis) tend to react unpredictably to suxamethonium. In myasthenia gravis, small doses of suxamethonium may be tried and the resulting effect monitored. In the other diseases listed non-depolarizers, cautiously used, are preferable. Cardiac arrest has been reported in patients with pseudohypertrophic muscular dystrophy (Duchenne tjrpe) and excessive muscle damage may be produced by suxamethonium in this condition. 

FleweUen EH, Bodensteiner JB. Anesthetic experience in a patient with hyperkalemic periodic paralysis. Anesthesiol Rev 1980 7 44. 

Pathological syndromes may result in muscular spasm, as seen in the exertional myopathies, or weakness, as seen in hyperkalemic periodic paralysis (HYPP). Similarly, infectious diseases may result in muscular rigidity (C. tetani infection (tetanus)) or paralysis (C. botulinum intoxication (botulism)). Overt rhabdomyolysis may result from the ingestion of the coccidiostats monensin, rumensin and lasalocid, or one of a number of plant mycotoxins. Dietary deficiencies of selenium or vitamin E have also been described as having severe deleterious effects on skeletal muscle health. 

The anticonvulsant phenytoin (diphenylhydantoin) has been used in horses to treat hyperkalemic periodic paralysis and rhabdomyolysis (see Ch. 8) and cardiac arrhythmias (see Ch. 12). It is not usually used as an anticonvulsant in horses. 

There are no published reports on the pharmacokinetics of the thiazide-type diuretics in horses. A bolus dose of a combination of dexamethasone (5 mg) and trichlormethiazide (200 mg), a product commonly used for treatment of udder edema in periparturient cattle, is occasionally used to treat edema in horses and there are anecdotal reports that it is efficacious. Hydrochlorothiazide (0.5- 0.7mg/kg orally twice daily) has also been used to enhance urinary potassium excretion and thereby limit the increase in serum potassium concentrations during an episode of hyperkalemic periodic paralysis in horses (Beech Lindborg 1996, Spier et al 1990 see Ch. 8). However, hydrochlorothiazide was less effective than acetazolamide (see below) and phenytoin in controlling the clinical signs, but it did limit the increase in the serum potassium ion concentrations during an oral potassium chloride challenge test (Beech Lindborg 1996). 

Hyperkalemic periodic paralysis in horses. Journal of the American Veterinary Medical Association 197 1009-1016... 

Sodium chloride solution has been advocated in hyperkalemia, in order to avoid the potassium-containing polyionic fluids (Table 17.4). However this does not apply to the horse in the absence of clinical signs of hyperkalemia and with the exception of horses with hyperkalemic periodic paralysis or with a ruptured bladder, the hyperkalemia is likely to reflect acidosis and polyionic fluids are probably appropriate. 

Cummins TR, Zhou J, Sigworth Fj et al 1993 Functional consequences of a Na channel mutation causing hyperkalemic periodic paralysis. Neuron 10 667—678... 

Fontaine B, Khurana TS, Hoffman EP et al 1990 Hyperkalemic periodic paralysis and the adult muscle sodium channel alpha-subunit gene. Science 250 1000-1002... 

Ptacek LJ, George AL Jr, Griggs RCet al 1991a Identification of a mutation in the gene causing hyperkalemic periodic paralysis. Cell 67 1021—1027... 

Ptacek LJ, Tyler F, Trimmer JS, Agnew WS, Leppert M et al 1991b Analysis in a large hyperkalemic periodic paralysis pedigree supports tight linkage to a sodium channel locus. Am J Hum Genet 49 378—382... 

Ptacek LJ, Trimmer JS, Agnew WS, Roberts JW, Petajan JH, Leppert M 1991c Paramyotonia congenita and hyperkalemic periodic paralysis map to the same sodium-channel gene locus. Am J Hum Genet 49 851-854... 

Ptacek LJ, Tawil R, Griggs RC et al 1994a Sodium channel mutations in acetazolamide-responsive myotonia congenita, paramyotonia congenita, and hyperkalemic periodic paralysis. Neurology 44 1500-1503... 

Hypokalemic periodic paralysis Due to defective gene for one type of DHPR. Hyperkalemic periodic paralysis Due to defects in a skeletal muscle sodium channel,... 

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