Hyperkalemic periodic paralysis is a rare medical condition characterized by periods of extreme muscle weakness or paralysis. While most cases of hyperkalemic periodic paralysis are associated with a genetic channelopathy, cases of secondary hyperkalemic periodic paralysis can pose a challenge for medical personnel in terms of timely recognition. Identification of this medical emergency early in its course is essential to preventing cardiac and neurological sequelae. We report a case of a 58-year-old female who presented with stroke-like symptoms and was found to have secondary hyperkalemic periodic paralysis attributed to the excess consumption of potatoes, a potassium-rich food. This case highlights the importance of considering hyperkalemic periodic paralysis early in the differentiation of patients with end-stage renal disease (ESRD) who present with muscle weakness and stroke-like symptoms.

Hypokalaemic periodic paralysis (HPP) is a rare disorder characterized by episodic attacks of muscle weakness and hypokalaemia. Numerous factors contributing to HPP have been identified, encompassing both hereditary and familial origins as well as acquired factors. In this context, we highlight thyrotoxicosis causing HPP. We present a case of a 40-year-old Asian individual who presented with episodes of sudden onset bilateral proximal limb weakness and palpitations. Laboratory investigations revealed severe hypokalaemia (serum potassium: 1.8 mmol/L). Immediate potassium replacement therapy alleviated symptoms. Further evaluation revealed a new diagnosis of hyperthyroidism, with subsequent treatment initiated (carbimazole and propranolol) preventing recurrence of symptoms. This case highlights the importance of recognizing HPP as a potential manifestation of thyroid dysfunction, particularly in individuals of Asian ethnicity.

Hyperkalemic periodic paralysis (HyperPP) is the rarer of two forms of potassium-associated familial paralysis characterized by episodic flaccid weakness secondary to an increase in serum potassium. The rarest of the dyskalemic paralyzes, the incidence of the hyperkalemic variety has been estimated to be 1:500,000. Known precipitating factors are potassium intake, fasting, hypothermia, infection, stress, rest after exercise, and anesthesia. The key to successful management is avoidance of triggering factors, vigilant monitoring of potassium, and aggressive treatment of hyperkalemia. We present a case of a 41-year-old male with HyperPP who underwent general anesthesia successfully.

BACKGROUND: Primary periodic paralysis (PPP) are rare inherited neuromuscular disorders including Hypokalemic periodic paralysis (HypoPP), Hyperkalemic periodic paralysis (HyperPP) and Andersen-Tawil syndrome (ATS) characterised by attacks of weakness or paralysis of skeletal muscles. Limited effective pharmacological treatments are available, and avoidance of lifestyle related triggers seems important.
OBJECTIVE: Our aim was to search and assess the scientific literature for information on trigger factors related to nutrition and physical activity in PPP.
METHODS: We searched Ovid Medline and Embase database for scientific papers published between January 1, 1990, to January 31, 2020.
RESULTS: We did not identify published observation or intervention studies evaluating effect of lifestyle changes on attacks. Current knowledge is based on case-reports, expert opinions, and retrospective case studies with inadequate methods for description of nutrition and physical activity. In HypoPP, high carbohydrate and salt intake, over-eating, alcohol, dehydration, hard physical activity, and rest after exercise are frequently reported triggers. Regarding HyperPP, fasting, intake of potassium, alcohol, cold foods or beverages, physical activity, and rest after exercise are frequently reported triggers. No nutrition related triggers are reported regarding ATS, exercise can however induce ventricular arrhythmias.
CONCLUSIONS: Our results support that dietary intake and physical activity may play a role in causing paralytic attacks in PPP, although the current scientific evidence is weak. To provide good evidence-based patient care, several lifestyle aspects need to be further assessed and described.

Periodic paralyses are a group of disorders characterized by episodes of muscle paralyses. They are mainly divided as primary (hereditary) and secondary (acquired) periodic paralyses. Primary periodic paralyses occur as a result of mutations in genes encoding subunits of muscle membrane channel proteins such as sodium, calcium, and potassium channels, resulting in impairment of their properties. Primary periodic paralyses are further classified on the basis of affected ion channels and other associated complications. Some of these periodic paralyses are hyperkalemic periodic paralysis (Na-channel mutation), hypokalemic periodic paralysis (Na- or Ca-channel mutation), Andersen\'s syndrome (K-channel mutation), etc.

Hyperkalemic periodic paralysis (hyperkalemic PP) is a rare muscle disease that has onset in infancy or early childhood and is manifested by transient episodes of paralysis. In this case we presented a young male adult with attacks of weakness, after commencement of the antiepileptic drug - Carbamazepine. We hypothesize that Carbamazepine, as voltage-gate sodium channel blocker, aggravated the symptoms of hyperkalemic PP, as sodium channelopathies, in this young-male-patient, trough influence on membrane depolarization.

Nondystrophic myotonias are disorders of Na+ (Nav1.4 or SCN4A) and Cl- (CLCN1) channels in skeletal muscles, and frequently show phenotype heterogeneity. The molecular mechanism underlying their pathophysiology and phenotype heterogeneity remains unclear. As zebrafish models have been recently exploited for studies of the pathophysiology and phenotype heterogeneity of various human genetic diseases, a zebrafish model may be useful for delineating nondystrophic myotonias. Here, we generated transgenic zebrafish expressing a human mutant allele of SCN4A, referred to as Tg(mylpfa:N440K), and needle electromyography revealed increased number of myotonic discharges and positive sharp waves in the muscles of Tg(mylpfa:N440K) than in controls. In addition, forced exercise test at a water temperature of 24 °C showed a decrease in the distance moved, time spent in and number of visits to the zone with stronger swimming resistance. Finally, a forced exercise test at a water temperature of 18 °C exhibited a higher number of dive-bombing periods and drifting-down behavior than in controls. These findings indicate that Tg(mylpfa:N440K) is a good vertebrate model of exercise- and cold-induced human nondystrophic myotonias. This zebrafish model may contribute to provide insight into the pathophysiology of myotonia in sodium channelopathy and could be used to explore a new therapeutic avenue.

To verify the diagnosis of channelopathies in two families and explore the mechanism of the overlap between periodic paralysis (PP) and paramyotonia congenita (PMC).
We have studied two cases with overlapping symptoms of episodic weakness and stiffness in our clinical center using a series of assessment including detailed medical history, careful physical examination, laboratory analyses, muscle biopsy, electrophysiological evaluation, and genetic analysis.
The first proband and part of his family with the overlap of PMC and hyperkalemic periodic paralysis (HyperPP) has been identified as c.2111C > T (T704M) substitution of the gene SCN4A. The second proband and part of his family with the overlap of PMC and hypokalemic periodic paralysis type 2 (HypoPP2) has been identified as c.4343G > A (R1448H) substitution of the gene SCN4A. In addition, one member of the second family with overlapping symptoms has been identified as a novel mutation c.2111C > T without the mutation c.4343G > A.
SCN4A gene mutations can cause the overlap of PMC and PP (especially the HypoPP2). The clinical symptoms of episodic weakness and stiffness could happen at a different time or temperature. Based on diagnosis assessments such as medical history and muscle biopsy, further evaluations on long-time exercise test, genetic analysis, and patch clamp electrophysiology test need to be done in order to verify the specific subtype of channelopathies. Furthermore, the improvement of one member in the pregnancy period can be used as a reference for the other female in the child-bearing period with T704M.

A 33-year-old man admitted to our hospital for the evaluation of progressive muscular atrophy of his left lower leg. From his childhood, he had suffered from transient attacks of limb paralysis and myalgia lasting about 1 hour. At age 30, the muscle weakness and atrophy of his left lower leg emerged and progressed gradually. Muscle MR images showed atrophy and fat replacement in left lower leg, and muscle biopsy revealed tubular aggregates (TA). Genetic analysis showed heterozygous c.2111C>T/p.T704M missense mutation of SCN4A gene, which causes hyperkalemic periodic paralysis (HyperPP). Although HyperPP is rare, it is quite critical for clinicians to recognize that the patients of HyperPP often present progressive myopathy. We emphasize the importance of paying attention to progressive myopathy and discuss the pathological mechanism of myopathy through this case report.

Hyperkalemic periodic paralysis (hyperKPP) is a muscle channelopathy characterized by recurrent paralytic attacks. Our previous study, in which we conducted whole-body muscle magnetic resonance imaging (MRI) in patients with hyperKPP, revealed muscle atrophy and fatty change in the lower extremity, especially in older persons. The aim of current study was to identify the progression of myopathy in hyperKPP patients had been assessed in the previous study. We performed lower-extremity muscle MRI in seven hyperKPP patients carrying the T704M mutation in the SCN4A gene at an interval of 30 months. Muscle atrophy, edematous change, fatty change, and fat fraction quantified using the Dixon technique were compared with the previous MRI findings. The lower-extremity MRI scan showed progressive muscle pathologic findings when compared with the previous study. Muscle atrophy, edematous change, and fatty change were prominent in the superficial posterior compartment of the lower leg. The follow-up lower-extremity muscle MRI findings provide evidence for chronic progressive myopathy and suggest the usefulness of MRI for assessing disease progression in patients with hyperKPP. This study is meaningful in terms of providing data showing the longitudinal changes of muscles in patients with periodic paralysis.