Periodic paralyses

Familial Hypokalemic Periodic Paralysis: Case Report

Hypokalemic periodic paralysis is a congenital disorder which is characterized by intermittent episodes of muscle weakness or paralysis. The attacks can occur everyday or once a year, may last for a few hours or for several days. Serum potassium level is low during the attack. But serum potassium levels are normal between two attacks. There is no potassium deficiency in the whole body. In this report, a 16 years old boy, whose grandfather, father and uncle had the same semptoms, and had his first attack of familial hypokalemic periodic paralysis following a grand exercise were presented according to the clinical and laboratory features.

Equine metabolic myopathies with emphasis on the diagnostic approach comparison with human myopathies A review

This review gives an overview of the presently known human and equine metabolic myopathies with emphasis on the diagnostic approach. Metabolic myopathies are muscle disorders caused by a biochemical defect of the skeletal muscle energy system, which results in inefficient muscle performance. Myopathies can arise in different levels of the metabolic system. In this review the metabolic myopathies are categorized in disorders of the carbohydrate metabolism, lipid metabolism, mitochondrial myopathies (other than those described in lipid metabolism), disorders of purine metabolism, primary disorders involving ion channels and electrolyte flux and secondary or acquired metabolic myopathies.

Phosphorylation and protonation of neighboring MiRP2 sites: function and pathophysiology of MiRP2-Kv3.4 potassium channels in periodic paralysis

MinK-related peptide 2 (MiRP2) and Kv3.4 subunits assemble in skeletal muscle to create subthreshold, voltage-gated potassium channels. MiRP2 acts on Kv3.4 to shift the voltage dependence of activation, speed recovery from inactivation, suppress cumulative inactivation and increase unitary conductance. We previously found an R83H missense mutation in MiRP2 that segregated with periodic paralysis in two families and diminished the effects of MiRP2 on Kv3.4. Here we show that MiRP2 has a single, functional PKC phosphorylation site at serine 82 and that normal MiRP2-Kv3.4 function requires phosphorylation of the site. The R83H variant does not prevent PKC phosphorylation of neighboring S82; rather, the change shifts the voltage dependence of activation and endows MiRP2-Kv3.4 channels with sensitivity to changes in intracellular pH across the physiological range. Thus, current passed by single R83H channels decreases as internal pH is lowered (pK(a) approximately 7.3, consistent with histidine protonation) whereas wild-type channels are largely insensitive. These findings identify a key regulatory domain in MiRP2 and suggest a mechanistic link between acidosis and episodes of periodic paralysis.

Genetics of cardiac arrhythmias and sudden cardiac death

This presentation deals with the molecular substrates of the inherited diseases leading to genetically determined cardiac arrhythmias and sudden death. In the first part of this article the current knowledge concerning the molecular basis of cardiac arrhythmias will be summarized. Second, we will discuss the most recent evidence showing that the picture of the molecular bases of cardiac arrhythmias is becoming progressively more complex. Thanks to the contribution of molecular genetics, the genetic bases, pathogenesis, and genotype-phenotype correlation of diseases--such as the long QT syndrome, the Brugada syndrome, progressive cardiac conduction defect (Lenegre disease), catecholaminergic polymorphic ventricular tachycardia, and Andersen syndrome--have been progressively unveiled and shown to have an extremely high degree of genetic heterogeneity. The evidence supporting this concept is outlined, with particular emphasis on the growing complexity of the molecular pathways that may lead to arrhythmias and sudden death, in terms of the relationships between genetic defect(s) and genotype(s), as well as gene-to-gene interactions. The current knowledge is reviewed, focusing on the evidence that a single clinical phenotype may be caused by different genetic substrates and, conversely, a single gene may cause very different phenotypes acting through different pathways.

Pyloromyotomy in a patient with paramyotonia congenita

A 2-mo-old infant with paramyotonia congenita was scheduled for pyloromyotomy and repair of inguinal hernia. Diagnosis of paramyotonia congenita was done with positive family history, myotonia at eyelids, provocation by cold, and electromyogram analysis. Anesthesia was induced via face mask with sevoflurane at 4 minimum alveolar anesthetic concentration in oxygen. Tracheal intubation was attempted without a neuromuscular relaxant. Anesthesia was maintained with sevoflurane at 0.5 minimum alveolar anesthetic concentration in oxygen and remifentanil infusion at a rate of 0.2 micro g. kg(-1). min(-1). After discontinuation of sevoflurane and remifentanil, the patient was awake and had full recovery of muscle activity.

IMPLICATIONS

The literature concerning general anesthesia in paramyotonic patients is limited. We report a case of paramyotonia congenita in a 2-mo-old male infant undergoing surgery for pyloric stenosis and inguinal hernia after an uneventful anesthesia.

Severe hypokalemia as a cause of acute transient paraplegia following electrical shock

Transient lower extremity paralysis has been previously reported following high voltage electrical injury. The following case report describes an unusual presentation of transient acute flaccid lower extremity paralysis following a high voltage electrical injury associated with profound hypokalemia and acid/base abnormalities similar to the periodic paralysis syndrome. The patient's symptoms resolved with correction of severe hypokalemia. Potential mechanisms for a metabolic neuromuscular disorder induced by electrical injury are proposed.