Review of the Diagnosis and Treatment of Periodic Paralysis

Hypokalemic periodic paralysis, a rare yet critical condition: A case report

Hypokalemic periodic paralysis (HPP) is a rare disease. Due to channelopathy caused by mutations in skeletal muscle ion channels, episodes of sudden flaccid muscle weakness and hypokalemia develop as a result of various trigger factors. The present study reports the case of a 25-year-old male patient with HPP admitted with acute onset numbness and paralysis in the extremities accompanying hypokalemia (2.66 mEq/l). The patient became asymptomatic following treatment with a potassium (K) supplement and was diagnosed with HPP. The present study describes this case of HPP in an aim to remind colleagues of the possibility of HPP in hypokalemic patients with muscle weakness and flaccid paralysis.

Unraveling an Uncommon Encounter: Hypokalemic Periodic Paralysis with Brugada Phenocopy Amidst Hypokalemia

Introduction

Hypokalemic periodic paralysis (HPP) presents a diagnostic challenge due to the painless muscle weakness it causes. This case discusses a patient with HPP along with electrocardiogram (ECG) findings of Brugada phenocopies (BrP) in the setting of hypokalemia. A review of the literature showed that it is the seventh documented example of BrP induced by hypokalemia alongside HPP.

Case description

A 43-year-old man presented to the emergency department with lower limb weakness. He attributed his symptoms to a substantial meal consumed after breaking his Ramadan fast, recalling a similar episode following heavy meals in the past. The patient was alert and oriented but demonstrated reduced strength in both upper and lower limbs. ECG revealed a Brugada type 1 pattern. Laboratory analysis revealed hypokalemia (2.5 mmol/l), elevated creatine kinase (326 U/l), and normal thyroid function. Following potassium supplementation, his symptoms resolved, and his ECG normalized.

Discussion

HPP occurs in the context of increased carbohydrate intake, potentially leading to rapid insulin release and activation of Na-K ATPase, enhancing cellular potassium absorption and lowering serum potassium levels. Symptoms range from weakness and fatigue to severe neuromuscular weakness and cardiac arrhythmias. Investigating hypokalemia requires excluding hypomagnesemia, thyroid function tests, and metabolic acidosis/alkalosis before considering HPP. Management involves gradual oral potassium repletion to avoid the risk of hyperkalemia associated with intravenous administration.

Conclusion

Clinicians should consider including HPP in differential diagnoses of patients presenting with weakness. In this case, electrophysiological evaluation suggested Brugada pattern induced by hypokalemia, which resolved with potassium supplementation.

LEARNING POINTS

This case highlights the rarity and diagnostic challenges of hypokalemic periodic paralysis, offering critical insights into recognizing and managing such conditions in clinical practice.The case also demonstrates the importance of identifying reversible electrocardiogram changes like Brugada patterns, aiding in differentiation from persistent arrhythmias and avoiding unnecessary interventions.

Familial hypokalemic periodic paralysis: a case induced by concurrent hyperthyroidism

BACKGROUND

Familial hypokalemic periodic paralysis (HypoPP) is an uncommon genetic disorder characterized by recurrent episodes of muscle weakness and hypokalemia, typically starting in early adulthood. The existence of hyperthyroidism in the presence of HypoPP is more strongly associated with a diagnosis of thyrotoxic periodic paralysis (TPP), with most cases occurring in Asian males with pathogenic KCNJ2 or KCNJ18 variants and without a family history of the condition. This case is novel due to the combination of familial HypoPP and hyperthyroidism induced by Graves' disease, a rare occurrence especially in non-Asian populations.

CASE PRESENTATION

A 40-year-old African American man presented with profound muscle weakness after consuming a high-salt meal. He had a significant family history of hyperthyroidism and hypokalemia. On examination, he showed profound weakness in all extremities. Laboratory tests confirmed hypokalemia and hyperthyroidism, and genetic testing identified a pathogenic variant in the CACNA1S gene (c.1583 G > A, p. R528H), with normal SCN4A, KCNJ2 and KCNJ18 sequencing. He was diagnosed with familial HypoPP and hyperthyroidism due to Graves' disease. He was started on PO methimazole 10 mg three times a day and PO acetazolamide 250 mg twice a day. He was advised to follow a low carbohydrate and low salt diet.

CONCLUSIONS

This case highlights the importance of considering a genetic basis for HypoPP in patients with a family history of the condition, even when hyperthyroidism is present. The combination of familial HypoPP and Graves' disease is rare and emphasizes the need for careful genetic and clinical evaluation in similar cases. Management should focus on correcting hypokalemia, treating hyperthyroidism, and lifestyle modifications to prevent recurrence.

Clinical, myopathological, and genetic features of two Chinese families with Andersen-Tawil syndrome

Purpose

To explore the clinical, muscle pathological, and pathogenic gene mutation characteristics of Andersen-Tawil Syndrome (ATS) and enhance the understanding of ATS among clinical practitioners.

Methods

Retrospective analysis of clinical data and muscle pathology of two ATS families, along with genetic testing for probands and some family members.

Results

In Family 1, spanning four generations, four individuals were affected, while Family 2 had two affected individuals across four generations. All six patients in both families experienced onset in childhood, presenting with periodic paralysis, arrhythmias, and craniofacial skeletal abnormalities. In Family 1, the proband's periodic paralysis was more triggered by low temperature and exercise, occurring several times a year, lasting 4-7 days. All three adult patients in Family 1 had a history of hypokalemia, and the frequency and severity of attacks were reduced after regular oral potassium supplement therapy. Two adult females in Family 1 experienced limb weakness triggered by stress, exertion, and premenstrual period, with milder symptoms than the proband. In Family 2, the proband's periodic paralysis typically occurred the day after excessive exertion, with a frequency of approximately 2-3 months. Two years prior, the proband developed arrhythmias without palpitations or chest tightness. The proband's brother experienced intermittent limb weakness during adolescence, remained untreated, and had sudden death at age 40. Physical examination revealed characteristic features in Family 1 and both probands: small mandible, wide eye spacing, and fifth-digit clinodactyly. Four adult patients were shorter in stature, while the growth status of a pediatric patient was indeterminate. Supplementary tests showed a history of hypokalemia during muscle weakness episodes in Family 1, while Family 2 patients had normal potassium levels during episodes. The long exercise tests were positive in both probands. Muscle MRI showed no significant abnormalities, but muscle pathology revealed rimmed vacuoles and tubular aggregates. Genetic testing identified KCNJ2 gene mutations in two probands and some of their family members, with c.407C > T (p.S136F) heterozygous mutation in Family 1 and c.652C > T (p.R218W) heterozygous mutation in Family 2.

Conclusion

Among the clinical symptoms of the patients with Andersen-Tawil Syndrome in this study, not everyone exhibits the full triad of signs: periodic paralysis is the most common initial symptom, craniofacial and digit skeletal abnormalities are characteristic signs, and ventricular arrhythmias pose the most serious potential risk. Given that these typical symptoms were observed in 5 out of 6 patients, clinicians should pay special attention to these typical symptoms, and patients with these symptoms should be followed up over time. Muscle biopsy May reveal pathological changes such as tubular aggregates, but genetic testing for KCNJ gene mutations remains a crucial diagnostic criterion for this syndrome.

The network of cardiac KIR2.1: its function, cellular regulation, electrical signaling, diseases and new drug avenues

The functioning of the human heart relies on complex electrical and communication systems that coordinate cardiac contractions and sustain rhythmicity. One of the key players contributing to this intricate system is the KIR2.1 potassium ion channel, which is encoded by the KCNJ2 gene. KIR2.1 channels exhibit abundant expression in both ventricular myocytes and Purkinje fibers, exerting an important role in maintaining the balance of intracellular potassium ion levels within the heart. And by stabilizing the resting membrane potential and contributing to action potential repolarization, these channels have an important role in cardiac excitability also. Either gain- or loss-of-function mutations, but also acquired impairments of their function, are implicated in the pathogenesis of diverse types of cardiac arrhythmias. In this review, we aim to elucidate the system functions of KIR2.1 channels related to cellular electrical signaling, communication, and their contributions to cardiovascular disease. Based on this knowledge, we will discuss existing and new pharmacological avenues to modulate their function.

High risk and low prevalence diseases: Botulism

INTRODUCTION

Botulism is a serious condition that carries with it a high rate of morbidity and mortality.

OBJECTIVE

This review highlights the pearls and pitfalls of botulism, including presentation, diagnosis, and management in the emergency department (ED) based on current evidence.

DISCUSSION

Botulism is a neuromuscular disorder caused by toxin production of clostridium species bacteria and is a challenging diagnosis that mimics several other conditions. Children account for the majority of patients, with a foodborne source most common, followed by wound sources, typically from intravenous drug injection. Classically, patients with botulism develop bilateral cranial nerve palsies and symmetric, bilateral, descending paralysis. However, patients may initially present with vague symptomatology, such as weakness and dry mouth, which can make diagnosis challenging. A careful history elucidating exposures such as intravenous drug use or consumption of non-commercial canned products can help differentiate botulism from other disorders causing neuromuscular weakness. If suspected, the Centers for Disease Control should be notified to mobilize antitoxin for treatment as soon as the diagnosis is suspected even prior to confirmatory testing. Antibiotics should be avoided in these patients, as they can potentiate toxin release, unless there is a concomitant infection requiring antibiotic therapy. Patients with botulism can develop respiratory compromise requiring emergent airway management. Prolonged neuromuscular blockade from botulism will lead to a variety of symptoms that require comprehensive intensive care unit level care.

CONCLUSION

An understanding of botulism and its many potential mimics can assist emergency clinicians in diagnosing and managing this deadly disease.

[Andersen-Tawil Syndrome, a differential of bidirectional ventricular tachycardia: a case report]

We present the case of a patient with Andersen-Tawil syndrome (ATS), a rare genetic disorder characterized by the presence of ventricular arrhythmias, skeletal dysmorphic features, and periodic muscle paralysis. The diagnosis was delayed due to the non-simultaneity of symptom presentation. The report highlights the importance of investigating neurological symptoms in the presence of ventricular arrhythmias of unclear origin or cardiac symptoms in patients with periodic paralysis. The diagnosis was confirmed by the identification of a mutation in the KCNJ2 gene (c.224C>T(p.Thr75Met)); this specific mutation has not been reported in the gnomAD database, suggesting a minor allele frequency (MAF) of less than 1%. The patient is currently managed pharmacologically with a beta-blocker and remains free of arrhythmias.

Pediatric and Familial Genetic Arrhythmia Syndromes: Evaluation of Bidirectional Ventricular Tachycardia-Differential Diagnosis

Bidirectional ventricular tachycardia is a unique arrhythmia that can herald lethal arrhythmia syndromes. Using cases based on real patient stories, this article examines 3 different presentations to help clinicians learn the differential diagnosis associated with this condition. Each associated genetic disorder will be briefly discussed, and valuable tips for distinguishing them from each other will be provided.

Diagnosis, management and outcomes of primary hypokalemic periodic paralysis during pregnancy

Primary hypokalaemic periodic paralysis during pregnancy has been rarely reported. Four pregnant women with the acute onset of flaccid paralysis presented between January 2018 and December 2021. Focussed history and physical examination helped an appropriate radiological and laboratory investigation plan to be made. All women recovered within 4-7 days of potassium supplementation. Supplemental potassium continued until delivery. A pain management plan with continuous epidural infusion helped in avoiding stress-induced hypokalaemia. None of the women developed an episode of muscle weakness during the intervening period. In conclusion, a focussed history and targeted laboratory investigation are needed to diagnose primary hypokalaemic periodic paralysis. Early administration of oral or intravenous potassium is crucial in improving fetomaternal outcomes.

Acquired hyperkalaemia leading to periodic paralysis: an emergency department perspective

Hyperkalaemia is one of the common electrolyte imbalances dealt with in the emergency department and is caused by extracellular accumulation of potassium ions above normal limits usually greater than 5.0-5.5 mmol/L. It is found in a total of 1-10% of hospitalised patients usually associated with chronic kidney disease and heart failure. The presentation can range from being asymptomatic to deadly arrhythmias. The appearance of symptoms depends on the rate of change rather than just the numerical values. The rare presentation includes periodic paralysis characterised by the sudden onset of short-term muscle weakness, stiffness or paralysis. Management goals are directed towards reducing potassium levels in emergency settings and later on avoiding the triggers for future attacks. In this case, we present a man in his 50s with the generalised weakness later on diagnosed as hyperkalaemic periodic paralysis secondary to tumour lysis syndrome. Emergency physicians dealing with common electrolyte imbalances should keep a sharp eye on their rare presentation and their precipitating factors and should act accordingly.

Functional effects of drugs and toxins interacting with NaV1.4

NaV1.4 is a voltage-gated sodium channel subtype that is predominantly expressed in skeletal muscle cells. It is essential for producing action potentials and stimulating muscle contraction, and mutations in NaV1.4 can cause various muscle disorders. The discovery of the cryo-EM structure of NaV1.4 in complex with β1 has opened new possibilities for designing drugs and toxins that target NaV1.4. In this review, we summarize the current understanding of channelopathies, the binding sites and functions of chemicals including medicine and toxins that interact with NaV1.4. These substances could be considered novel candidate compounds or tools to develop more potent and selective drugs targeting NaV1.4. Therefore, studying NaV1.4 pharmacology is both theoretically and practically meaningful.

Genetic analysis of 37 cases with primary periodic paralysis in Chinese patients

BACKGROUND

Primary periodic paralysis (PPP) is an inherited disorders of ion channel dysfunction characterized by recurrent episodes of flaccid muscle weakness, which can classified as hypokalemic (HypoPP), normokalemic (NormoPP), or hyperkalemic (HyperPP) according to the potassium level during the paralytic attacks. However, PPP is charactered by remarkable clinical and genetic heterogeneity, and the diagnosis of suspected patients is based on the characteristic clinical presentation then confirmed by genetic testing. At present, there are only limited cohort studies on PPP in the Chinese population.

RESULTS

We included 37 patients with a clinical diagnosis of PPP. Eleven (29.7%) patients were tested using a specific gene panel and 26 (70.3%) by the whole-exome sequencing (WES). Twenty-two cases had a genetic variant identified, representing a diagnostic rate of 59.5% (22/37). All the identified mutations were either in the SCN4A or the CACNA1S gene. The overall detection rate was comparable between the panel (54.5%: 6/11) and WES (61.5%: 16/26). The remaining patients unresolved through panel sequencing were further analyzed by WES, without the detection of any mutation. The novel atypical splicing variant c.2020-5G > A affects the normal splicing of the SCN4A mRNA, which was confirmed by minigene splicing assay. Among 21 patients with HypoPP, 15 patients were classified as HypoPP-2 with SCN4A variants, and 6 HypoPP-1 patients had CACNA1S variants.

CONCLUSIONS

Our results suggest that SCN4A alleles are the main cause in our cohort, with the remainder caused by CACNA1S alleles, which are the predominant cause in Europe and the United States. Additionally, this study identified 3 novel SCN4A and 2 novel CACNA1S variants, broadening the mutation spectrum of genes associated with PPP.

A retrospective study of accuracy and usefulness of electrophysiological exercise tests

OBJECTIVES

This study aimed to determine the usefulness of electrophysiological exercise tests. The significance of slightly abnormal exercise tests was also examined.

METHODS

We identified all the patients who had undergone exercise testing between February 2007 to June 2022 in Tampere University Hospital, Finland. Their medical records after diagnostic workup and exercise test reports were reviewed. A binary logistic regression was performed to evaluate the association between positive test result in short exercise test, long exercise test, or short exercise test with cooling and genetically confirmed skeletal muscle channelopathy or myotonic disorder.

RESULTS

We identified 256 patients. 27 patients were diagnosed with nondystrophic myotonia, periodic paralysis, myotonic dystrophy type 1, myotonic dystrophy type 2, or other specified myopathy. 14 patients were suspected to have a skeletal muscle channelopathy, but pathogenic variants could not be identified. The remaining 215 patients were diagnosed with other conditions than skeletal muscle channelopathy or myotonic disorder. The combined sensitivity of exercise tests was 59.3% and specificity 99.1%. Abnormal exercise test result was associated with increased risk of skeletal muscle channelopathy or myotonic disorder (OR 164.3, 95% CI 28.3-954.6, p < 0.001).

CONCLUSIONS

Electrophysiological exercise test is not optimal to exclude skeletal muscle channelopathy. It may be useful if a skeletal muscle channelopathy is suspected and genetic testing is negative or indeterminate and further evidence is required. Slightly abnormal exercise test results are possible in various conditions and result from different aetiologies. There is a demand for neurophysiological studies with higher sensitivity to detect skeletal muscle channelopathies.

Crossover randomized controlled trial of bumetanide to rescue an attack of exercise induced hand weakness in hypokalaemic periodic paralysis

The aim of this study was to establish whether bumetanide can abort an acute attack of weakness in patients with HypoPP. This was a randomised, double-blind, cross-over, placebo-controlled phase II clinical trial. Focal attack of weakness was induced by isometric exercise of ADM followed by rest (McManis protocol). Participants had two study visits and received either placebo or 2 mg bumetanide at attack onset (defined as 40 % decrement in the abductor digiti minimi CMAP amplitude from peak). CMAP measurements assessed attack severity and duration. Nine participants completed both visits. CMAP percentage of peak amplitudes in the bumetanide (40.6 %) versus placebo (34.9 %) group at 1hr following treatment did not differ significantly (estimated effect difference 5.9 % (95 % CI: (-5.7 %; 17.5 %), p = 0.27, primary outcome). CMAP amplitudes assessed by the area under the curve for early (0-2hr post-treatment) and late (2-4 h post-treatment) efficacy were not statistically different between bumetanide and placebo (early effect estimate 0.043, p = 0.3; late effect estimate 0.085, p = 0.1). Two participants recovered from the attack following bumetanide intake; none recovered following placebo. Bumetanide was well tolerated but not efficacious to rescue a focal attack in an immobilised hand in the majority of patients, although data supports further studies of this agent.

Expression and electrophysiological characteristics of VGSC during mouse myoblasts differentiation

Voltage-gated sodium channels (VGSC) are essential for triggering and relaying action potentials (AP), which perform critical functions in a variety of physiological processes, such as controlling muscle contractions and facilitating the release of neurotransmitters. In this study, we used a mouse C2C12 cell differentiation model to study the molecular expression and channel dynamics of VGSC and to investigate the exact role of VGSC in the development of muscle regeneration. Immunofluorescence, Real-time quantitative polymerase chain reaction, Western blot, and whole-cell patch clamp were employed for this purpose in mouse myoblasts. The findings revealed an increase in intracellular sodium concentration, NaV1.4 gene expression, and protein expression with the progress of differentiation (days 0, 1, 3, 5 and 7). Furthermore, VGSC dynamics exhibit the following characteristics: ① The increase of sodium current (INa); ② The decrease in the activation threshold and the voltage trigger maximum of INa; ③ A positive shift in the steady-state inactivation curve; ④ The recovery of INa during repolarization is delayed, the activity-dependent decay rate of INa was accelerated, and the proportionate amount of the fraction of activated channels was reduced. Based on these results, it is postulated that the activation threshold of AP could be decreased, and the refractory period could be extended with the extension of differentiation duration, which may contribute to muscle contraction. Taken together, VGSC provides a theoretical and empirical basis for exploring potential targets for neuromuscular diseases and other therapeutic muscle regeneration dysfunctions.

Periodic paralysis

Periodic paralysis is a rare, dominantly inherited disorder of skeletal muscle in which episodic attacks of weakness are caused by a transient impairment of fiber excitability. Attacks of weakness are often elicited by characteristic environmental triggers, which were the basis for clinically delineating subtypes of periodic paralysis and are an important distinction for optimal disease management. All forms of familial periodic paralysis are caused by mutations of ion channels, often selectively expressed in skeletal muscle, that destabilize the resting potential. The missense mutations usually alter channel function through gain-of-function changes rather than producing a complete loss-of-function null. The knowledge of which channel gene harbors a variant, whether that variant is expected to (or known to) alter function, and how altered function impairs fiber excitability aides in the interpretation of patient signs and symptoms, the interpretation of gene test results, and how to optimize therapeutic intervention for symptom management and improve quality of life.

Physiotherapy Strategies in Hypokalemic Periodic Paralysis: A Case Report

The rare neuromuscular disease known as hypokalemic periodic paralysis (hypoKPP), which results in severe muscle weakness in the extremities, is brought on by abnormalities in potassium transport within cells. Laboratory testing is confirmatory, which reveals notably low potassium levels, causing paralysis, which improves once the low potassium is restored. The patient generally complains of muscle weakness with difficulty in performing activities of daily living and impaired participation in functional tasks, with few suffering from coexisting sensory impairments. Physiotherapy generally plays a symptomatic role with motion exercises for the affected muscle groups. There is no standardized physiotherapy protocol for disease-specific impairments. A 46-year-old man complained of bilateral upper and lower limb muscular weakness and was admitted to the neurology ward. The patient also complained of having tingling numbness throughout their entire limbs and had experienced similar episodes of symptoms six months prior. During laboratory evaluation, a significantly low potassium level was found, leading to a diagnosis of hypoKPP. Following medical management, neurophysiotherapy was initiated. Physiotherapy strategy shows significant improvement in muscular strength and functional activities. Thus, this case report concludes that physiotherapy plays a vital role in managing hypoKPP by enhancing muscular strength, functional activities, and quality of life.

Thyrotoxic periodic paralysis presenting with quadriparesis and hyperreflexia

Thyrotoxic periodic paralysis (TPP) is a rare complication of hyperthyroidism that manifests as painless flaccid paralysis. An East Asian man in his late 20s presented to the emergency department with an acute onset of quadriparesis associated with hypertonia and hyperreflexia. His initial symptoms and signs suggested involvement of the brain and spinal cord; however, MRI of the neuroaxis was normal. His serum potassium concentration was low, and thyroid test results were consistent with hyperthyroidism. The patient was diagnosed with TPP associated with Graves' disease and was treated with potassium supplementation, propranolol and methimazole. Motor strength improved to his baseline level of power; bulk was normal, and tone was increased. Although flaccid paralysis is a typical presentation of TPP, brisk reflexes and muscle spasticity cannot rule out this condition. This case highlights the importance of considering TPP as a possible diagnosis in patients presenting with acute quadriparesis.

CACNA1S Variant Associated With a Myalgic Myopathy Phenotype

BACKGROUND AND OBJECTIVES

This study aimed to characterize the phenotype of a novel myalgic myopathy encountered in a Finnish family.

METHODS

Four symptomatic and 3 asymptomatic individuals from 2 generations underwent clinical, neurophysiologic, imaging, and muscle biopsy examinations. Targeted sequencing of all known myopathy genes was performed.

RESULTS

A very rare CACNA1S gene variant c.2893G>C (p.E965Q) was identified in the family. The symptomatic patients presented with exercise-induced myalgia, cramping, muscle stiffness, and fatigue and eventually developed muscle weakness. Examinations revealed mild ptosis and unusual muscle hypertrophy in the upper limbs. In the most advanced disease stage, muscle weakness and muscle atrophy of the limbs were evident. In some patients, muscle biopsy showed mild myopathic findings and creatine kinase levels were slightly elevated.

DISCUSSION

Myalgia is a very common symptom affecting quality of life. Widespread myalgia may be confused with other myalgic syndromes such as fibromyalgia. In this study, we show that variants in CACNA1S gene may be one cause of severe exercise-induced myalgia.

A novel CACNA1S gene variant in a child with hypokalemic periodic paralysis: a case report and literature review

BACKGROUND

The CACNA1S gene encodes the alpha 1 S-subunit of the voltage-gated calcium channel, which is primarily expressed in the skeletal muscle cells. Pathogenic variants of CACNA1S can cause hypokalemic periodic paralysis (HypoPP), malignant hyperthermia susceptibility, and congenital myopathy. We aimed to study the clinical and molecular features of a male child with a CACNA1S variant and depict the molecular sub-regional characteristics of different phenotypes associated with CACNA1S variants.

CASE PRESENTATION

We presented a case of HypoPP with recurrent muscle weakness and hypokalemia. Genetic analyses of the family members revealed that the proband had a novel c.497 C > A (p.Ala166Asp) variant of CACNA1S, which was inherited from his father. The diagnosis of HypoPP was established in the proband as he met the consensus diagnostic criteria. The patient and his parents were informed to avoid the classical triggers of HypoPP. The attacks of the patient are prevented by lifestyle changes and nutritional counseling. We also showed the molecular sub-regional location of the variants of CACNA1S which was associated with different phenotypes.

CONCLUSIONS

Our results identified a new variant of CACNA1S and expanded the spectrum of variants associated with HypoPP. Early genetic diagnosis can help avoid diagnostic delays, perform genetic counseling, provide proper treatment, and reduce morbidity and mortality.

Muscle MRI in periodic paralysis shows myopathy is common and correlates with intramuscular fat accumulation

INTRODUCTION/AIMS

The periodic paralyses are muscle channelopathies: hypokalemic periodic paralysis (CACNA1S and SCN4A variants), hyperkalemic periodic paralysis (SCN4A variants), and Andersen-Tawil syndrome (KCNJ2). Both episodic weakness and disabling fixed weakness can occur. Little literature exists on magnetic resonance imaging (MRI) in muscle channelopathies. We undertake muscle MRI across all subsets of periodic paralysis and correlate with clinical features.

METHODS

A total of 45 participants and eight healthy controls were enrolled and underwent T1-weighted and short-tau-inversion-recovery (STIR) MRI imaging of leg muscles. Muscles were scored using the modified Mercuri Scale.

RESULTS

A total of 17 patients had CACNA1S variants, 16 SCN4A, and 12 KCNJ2. Thirty-one (69%) had weakness, and 9 (20%) required a gait-aid/wheelchair. A total of 78% of patients had intramuscular fat accumulation on MRI. Patients with SCN4A variants were most severely affected. In SCN4A, the anterior thigh and posterior calf were more affected, in contrast to the posterior thigh and posterior calf in KCNJ2. We identified a pattern of peri-tendinous STIR hyperintensity in nine patients. There were moderate correlations between Mercuri, STIR scores, and age. Intramuscular fat accumulation was seen in seven patients with no fixed weakness.

DISCUSSION

We demonstrate a significant burden of disease in patients with periodic paralyses. MRI intramuscular fat accumulation may be helpful in detecting early muscle involvement, particularly in those without fixed weakness. Longitudinal studies are needed to assess the role of muscle MRI in quantifying disease progression over time and as a potential biomarker in clinical trials.

Newly Diagnosed Hypokalemic Periodic Paralysis Triggered by COVID-19

Hypokalemic periodic paralysis (HypoPP) is a rare genetic disorder characterized by low potassium levels and episodic periods of muscle weakness. HypoPP has previously been attributed to numerous viral infections; however, cases related to coronavirus disease 2019 (COVID-19) are extremely limited. The current case is thus unique and involves a healthy 23-year-old male who presented to the emergency department after several uncharacteristic falls and three days of upper and lower extremity weakness. Initial labs revealed a potassium level of 1.1 mmol/L as well as being COVID-19 positive. Potassium supplementation helped stabilize his levels and relieved all of his symptoms. Based on an extensive clinical workup and significant family history of the mother and maternal grandmother with weakness in the setting of hypokalemia, a diagnosis of HypoPP was made. Upon discharge, he was placed on potassium-sparing diuretics to help prevent further symptom relapse and advised to complete genetic testing. With the high likelihood of the virus being endemic for years to come, clinicians should remember to consider HypoPP with patients with muscle weakness, especially in patients with concurrent COVID-19 infection, to minimize unnecessary workup and prevent potentially life-threatening symptoms of hypokalemia.

Case report: A novel CACNA1S mutation associated with hypokalemic periodic paralysis

Background

Hypokalemic periodic paralysis (HypoKPP) is a rare neuromuscular genetic disorder causing recurrent episodes of flaccid paralysis. Most cases are associated with CACNA1S mutation, causing defect of calcium channel and subsequent impairment of muscle functions. Due to defined management approaches early diagnosis is crucial for promptly treatment and prevention new attacks.

Materials and methods

We report a case of HypoKPP associated with previously unreported mutation in CACNA1S gene (p.R900M). Molecular modeling of CaV1.1 was applied to evaluate its pathogenicity.

Results

As a patient referred between attacks neurological status, laboratory and neurophysiological examination were unremarkable. Molecular modeling predicted that the p.R900M mutation affects the process of calcium channels activation.

Conclusion

Novel CACNA1S mutation, associated with HypoKPP was identified. Monte-Carlo energy minimization of the CaV1.1 model supported the association of this mutation with this disease.

An Instance of Hypokalemic Periodic Paralysis in Adolescent Brothers: A Case Report

Hypokalemic periodic paralysis (HypoPP) is a rare autosomal dominant disease caused by mutations in either calcium or sodium transmembrane voltage-gated ion channels of skeletal muscle or endoplasmic reticulum. Most cases of HypoPP are associated with a mutation in the gene encoding a calcium channel, the CACNA1S gene. Mutations in the channels create leakage currents that disrupt resting potential and depolarize the muscle fiber resulting in transient flaccid paralysis and low extracellular potassium (K+). Patients experience episodes of muscle paralysis typically provoked by exertion and diet. Treatment focuses on the prevention of such episodes with carbonic-anhydrase inhibitors or potassium-sparing diuretics as well as to treatment of acute episodes with oral K+ supplementation. Due to the rarity of the disease, the literature surrounding the disease and pharmacological management is limited. We present a case of two adolescent brothers who present with a confirmed diagnosis of periodic episodes of paralysis and are seeking treatment. Both brothers experience paralytic episodes provoked by acute changes in diet and exercise. However, the lack of literature and treatment guidelines surrounding the disease emphasizes the importance of documenting cases and the effectiveness of treatment outcomes. Additionally, it reminds providers to keep HypoPP on the differential when faced with a young patient experiencing paralytic episodes.

Parent-of-Origin Effect on the Age at Symptom Onset in Myotonic Dystrophy Type 2

Background and Objectives

The existence of clinical anticipation, congenital form, and parent-of-origin effect in myotonic dystrophy type 2 (DM2) remains uncertain. Here, we aimed at investigating whether there is a parent-of-origin effect on the age at the first DM2-related clinical manifestation.

Methods

We identified patients with genetically confirmed DM2 with known parental inheritance from (1) the electronic medical records of our institutions and (2) a systematic review of the literature following the PRISMA 2020 guidelines and recorded their age at and type of first disease-related symptom. We also interrogated the Myotonic Dystrophy Foundation Family Registry (MDFFR) for patients with DM2 who completed a survey including questions about parental inheritance and age at the first medical problem which they related to their DM2 diagnosis.

Results

A total of 26 patients with DM2 from 18 families were identified at our institutions as having maternal (n = 14) or paternal (n = 12) inheritance of the disease, whereas our systematic review of the literature rendered a total of 61 patients with DM2 from 41 families reported by 24 eligible articles as having maternal (n = 40) or paternal (n = 21) inheritance of the disease. Both cohorts were combined for downstream analyses. Up to 61% and 58% of patients had muscle-related symptoms as the first disease manifestation in maternally and paternally inherited DM2 subgroups, respectively. Four patients developed hypotonia at birth and/or delayed motor milestones early in life, and 7 had nonmuscular presentations (2 had cardiac events within the second decade of life and 5 had cataracts), all of them with maternal inheritance. A maternal inheritance was associated with an earlier (within the first 3 decades of life) age at symptom onset relative to a paternal inheritance in this combined cohort, and this association was independent of the patient's sex (OR [95% CI] = 4.245 [1.429-13.820], p = 0.0117). However, this association was not observed in the MDFFR DM2 cohort (n = 127), possibly because age at onset was self-reported, and the information about the type of first symptom or medical problem that patients related to DM2 was lacking.

Discussion

A maternal inheritance may increase the risk of an early DM2 onset and of cataracts and cardiovascular events as first DM2 manifestations.

Molecular stratification of arrhythmogenic mechanisms in the Andersen Tawil syndrome

Andersen-Tawil syndrome (ATS) is a rare inheritable disease associated with loss-of-function mutations in KCNJ2, the gene coding the strong inward rectifier potassium channel Kir2.1, which forms an essential membrane protein controlling cardiac excitability. ATS is usually marked by a triad of periodic paralysis, life-threatening cardiac arrhythmias and dysmorphic features, but its expression is variable and not all patients with a phenotype linked to ATS have a known genetic alteration. The mechanisms underlying this arrhythmogenic syndrome are poorly understood. Knowing such mechanisms would be essential to distinguish ATS from other channelopathies with overlapping phenotypes and to develop individualized therapies. For example, the recently suggested role of Kir2.1 as a countercurrent to sarcoplasmic calcium reuptake might explain the arrhythmogenic mechanisms of ATS and its overlap with catecholaminergic polymorphic ventricular tachycardia. Here we summarize current knowledge on the mechanisms of arrhythmias leading to sudden cardiac death in ATS. We first provide an overview of the syndrome and its pathophysiology, from the patient's bedside to the protein and discuss the role of essential regulators and interactors that could play a role in cases of ATS. The review highlights novel ideas related to some post-translational channel interactions with partner proteins that might help define the molecular bases of the arrhythmia phenotype. We then propose a new all-embracing classification of the currently known ATS loss-of-function mutations according to their position in the Kir2.1 channel structure and their functional implications. We also discuss specific ATS pathogenic variants, their clinical manifestations, and treatment stratification. The goal is to provide a deeper mechanistic understanding of the syndrome toward the development of novel targets and personalized treatment strategies.

An Interesting Case of Weakness and Atrial Tachycardia in the Emergency Department: Thinking Beyond Hearts and Minds

Thyrotoxic periodic paralysis is a rare but life-threatening presentation of hyperthyroidism that manifests with sudden, painless episodes of muscle weakness due to hypokalemia. We present the case of a middle-aged Middle Eastern female who attended our Emergency Department with sudden onset weakness to the lower limbs, resulting in her inability to walk. She had a power of 1/5 in the lower limbs, and subsequent investigations showed a low potassium level, and primary hyperthyroidism secondary to Grave's disease was diagnosed. A 12-lead electrocardiogram showed atrial flutter with a variable block, along with U waves. The patient reverted to sinus rhythm following administration of potassium replacement and was also treated with Propanalol and Carbimazole. The patient made a full neurological recovery.  Emergency physicians and all frontline healthcare workers should be aware that electrolyte problems can cause paralysis. Furthermore, hypokalemic periodic paralysis can be caused by an undiagnosed thyrotoxic state. Be aware that if left untreated, hypokalemia can cause serious atrial and ventricular arrhythmias. Achieving a euthyroid state and blunting hyperadrenergic stimulation, in addition to replacing potassium, all help to fully reverse muscle weakness.

Steroid-induced hypokalemic periodic paralysis: a case report and literature review

BACKGROUND

Hypokalemic periodic paralysis (HPP) is a rare channelopathy characterized by episodic attacks of acute muscle weakness concomitant with hypokalemia. The etiology of hypokalemia is the shift of potassium into the cells, and the clinical symptoms resolve when potassium starts to leak back to the serum. Most of the time, the underlying ion channel defects are well compensated, and an additional trigger is often required to initiate an attack. Well-known trigger factors include carbohydrate-rich meals, exercise followed by rest, stress, cold weather, and alcohol consumption.

CASE PRESENTATION

Here, we present the case of a 26-year-old Asian man who suffered from an acute onset of bilateral lower limb weakness with hypokalemia following dexamethasone injection. He was diagnosed with HPP.

CONCLUSIONS

We would like to remind physicians to think of steroids as an unusual precipitating factor while managing patients with HPP, per results of this case study.

Hypothalamic hypernatremic myopathy: A single-center case series

INTRODUCTION/AIMS

Hypernatremia myopathy is a rare disease often unrecognized by clinicians. This study aimed to present a case series of hypernatremic myopathy with an emphasis on profiling its clinical characteristics and exploring its pathogenesis.

METHODS

We reviewed seven patients with hypernatremic myopathy and reported their demographic data, etiology, clinical manifestations, and laboratory and electrophysiological characteristics. A muscle biopsy was performed on one patient.

RESULTS

All patients had hypothalamic lesions as the cause of the hypernatremia including craniopharyngioma, germinoma, pituitary adenoma, Langerhans cell histiocytosis, and glioma. The clinical manifestations varied from mild weakness to complete paralysis. Myalgia and muscle cramps were also observed. Four of the patients had rhabdomyolysis on admission and developed acute kidney injury. All patients had markedly elevated serum creatine kinase (CK) and sodium levels. There was a significant positive correlation between serum sodium and CK levels. A high prevalence of hypopituitarism in different axes was observed in our study. Central hypogonadism (5 of 7), central hypothyroidism (3 of 7), and central diabetes insipidus (3 of 7) were the most common manifestations of hypothalamic dysfunction. Myopathic changes were observed on needle electromyography. The muscle biopsy of one patient showed diffuse necrotic fibers and scattered hypercontracted fibers with increased ragged red fibers.

DISCUSSION

Hypernatremia myopathy should be considered in hypernatremic patients with muscle weakness and myalgia. Rhabdomyolysis frequently occurs and may lead to acute kidney injury in hypernatremia myopathy. Testing of hormone levels and performance of brain magnetic resonance imaging for possible hypothalamic lesions is strongly recommended.

Hypokalemic periodic paralysis presenting as asymmetric focal flaccid paralysis: A case report and literature review

Patients with the most common form of hypokalemic periodic paralysis (HypoKPP) exhibit symmetrical limb weakness. However, few patients present with asymmetric limb weakness. Here, we describe a unique case of HypoKPP presenting as asymmetric focal flaccid paralysis. In addition, a literature review is performed to provide a perspective for clinical management of similar cases. We present a detailed characterization of this rare type of HypoKPP. The initial presentation was right hand weakness, which progressed to bilateral lower limb weakness. Neurological examination showed that the affected muscles were uniquely confined to specific nerve innervation, i.e., right distal median nerve-innervated muscle, right deep peroneal nerve-innervated muscle and left side. The patient's serum level of potassium was lower than normal; the decline of long exercise test (LET) was higher than normal range; neurophysiological assessment revealed low amplitude compound muscle action potential (CMAP) during attack, the CMAP and patient's weakness rapidly returned to normal level after potassium supplementation. Therefore, HypoKPP can be formally diagnosed based on neurological examination, medical history, timely neural electrophysiological examinations and measurement of blood potassium level.

Clinical and Pathologic Features of Congenital Myasthenic Syndromes Caused by 35 Genes-A Comprehensive Review

Congenital myasthenic syndromes (CMS) are a heterogeneous group of disorders characterized by impaired neuromuscular signal transmission due to germline pathogenic variants in genes expressed at the neuromuscular junction (NMJ). A total of 35 genes have been reported in CMS (AGRN, ALG14, ALG2, CHAT, CHD8, CHRNA1, CHRNB1, CHRND, CHRNE, CHRNG, COL13A1, COLQ, DOK7, DPAGT1, GFPT1, GMPPB, LAMA5, LAMB2, LRP4, MUSK, MYO9A, PLEC, PREPL, PURA, RAPSN, RPH3A, SCN4A, SLC18A3, SLC25A1, SLC5A7, SNAP25, SYT2, TOR1AIP1, UNC13A, VAMP1). The 35 genes can be classified into 14 groups according to the pathomechanical, clinical, and therapeutic features of CMS patients. Measurement of compound muscle action potentials elicited by repetitive nerve stimulation is required to diagnose CMS. Clinical and electrophysiological features are not sufficient to identify a defective molecule, and genetic studies are always required for accurate diagnosis. From a pharmacological point of view, cholinesterase inhibitors are effective in most groups of CMS, but are contraindicated in some groups of CMS. Similarly, ephedrine, salbutamol (albuterol), amifampridine are effective in most but not all groups of CMS. This review extensively covers pathomechanical and clinical features of CMS by citing 442 relevant articles.

Thyrotoxic periodic paralysis associated with lactic metabolic acidosis: Case report of an African man and review of literature

BACKGROUND

Thyrotoxic periodic paralysis (TPP) is a rare and most often acquired subtype of hypokalemic periodic paralysis. The association of varying degrees of muscle weakness, hyperthyroidism and hypokalemia characterizes it. The treatment requires potassium supplementation, control of hyperthyroidism and prevention measures. It is a frequent disease in Asian men, but much rare in Caucasian or African populations. This is the first report of TPP associated with lactic metabolic acidosis in an African man.

CASE PRESENTATION

A 23 year-old African man, native from Morocco, with recurrent episodes of tetraparesis for eleven months, and abdominal pain, was referred for evaluation. Biochemical investigations showed severe hypokalemia associated with hyperthyroidism and lactic metabolic acidosis. His EKG showed signs of hypokalemia such as sinus tachycardia and U waves. After potassium supplementation, neurological recuperation was quick and complete. Thyroid ultrasound identified a hypoechogenic and hypervascularized goiter, associated with high levels of thyroid antibodies, in favor of Grave's disease. With antithyroid drugs and life-style changes, the patient did not have any other attack.

REVIEW OF LITERATURE

In addition to the case report, this article presents an extended review of literature, from the first large study reporting the diagnosis and incidence of TPP in 1957 to nowadays. Are reported here the latest information concerning epidemiology, clinical manifestations, complementary examinations, management and genetic finding. The lactic acidosis observed initially is exceptional, never described in TPP. TPP is a diagnostic and therapeutic emergency, requiring careful potassium supplementation, in order to avoid the risk of the onset of rebound hyperkalemia, to be maintained until the etiological treatment is effective. Paraclinical assessment with emergency EKG and electromyogram are essential to assess the impact.

DISCUSSION

It is essential in the face of any hypokalaemic periodic paralysis, including in non-Asian subjects, to search hyperthyroidism.

CONCLUSIONS

This report demonstrates the importance of thyroid testing in case of acute muscle weakness, even in non-Asian patients in order to diagnose TPP. This is a rare but possible etiology, to be distinguished from the familial form of hypokalemic periodic paralysis. It also questions on the impact of TPP on energetic metabolism, in particular on lactic metabolism.

Drug repurposing in skeletal muscle ion channelopathies

Skeletal muscle ion channelopathies are rare genetic diseases mainly characterized by myotonia (muscle stiffness) or periodic paralysis (muscle weakness). Here, we reviewed the available therapeutic options in non-dystrophic myotonias (NDM) and periodic paralyses (PP), which consists essentially in drug repositioning to address stiffness or weakness attacks. Empirical use followed by successful randomized clinical trials eventually led to the orphan drug designation and marketing authorization granting of mexiletine for NDM and dichlorphenamide for PP. Yet, these treatments neither consider the genetic cause of the diseases nor address the individual variability in drug response. Thus, ongoing research aims at the identification of repurposed drugs alternative to mexiletine and dichlorphenamide to allow personalization of treatment. This review highlights how drug repurposing may represent an efficient strategy in rare diseases, allowing reduction of drug development time and costs in a context in which the return on investment may be particularly challenging.

Thyrotoxic Periodic Paralysis With Severe Hypokalemia Precipitated by Acute Alcohol Intoxication in a Patient With Graves' Disease

We present a case of a 29-year-old male who presented with thyrotoxic periodic paralysis (TPP) precipitated by acute alcohol intoxication. TPP is an endocrine emergency that presents with an episode of acute flaccid paralysis with hypokalemia in the setting of thyrotoxicosis. Individuals who present with TPP are thought to have an underlying genetic predisposition. Overactivation of the Na⁺/K⁺ ATPase channel leads to large-scale intracellular shifts in potassium, leading to low serum levels and the clinical manifestations of TPP. Severe hypokalemia can lead to life-threatening complications such as ventricular arrhythmias and respiratory failure. Therefore, timely recognition and management are essential in cases of TPP. In addition, understanding the precipitating factors is necessary for adequate counseling of these patients to prevent further episodes.

Retigabine suppresses loss of force in mouse models of hypokalaemic periodic paralysis

Recurrent episodes of weakness in periodic paralysis are caused by intermittent loss of muscle fibre excitability, as a consequence of sustained depolarization of the resting potential. Repolarization is favoured by increasing the fibre permeability to potassium. Based on this principle, we tested the efficacy of retigabine, a potassium channel opener, to suppress the loss of force induced by a low-K+ challenge in hypokalaemic periodic paralysis (HypoPP). Retigabine can prevent the episodic loss of force in HypoPP. Knock-in mutant mouse models of HypoPP (Cacna1s p.R528H and Scn4a p.R669H) were used to determine whether pre-treatment with retigabine prevented the loss of force, or post-treatment hastened recovery of force for a low-K+ challenge in an ex vivo contraction assay. Retigabine completely prevents the loss of force induced by a 2 mM K+ challenge (protection) in our mouse models of HypoPP, with 50% inhibitory concentrations of 0.8 ± 0.13 μM and 2.2 ± 0.42 μM for NaV1.4-R669H and CaV1.1-R528H, respectively. In comparison, the effective concentration for the KATP channel opener pinacidil was 10-fold higher. Application of retigabine also reversed the loss of force (rescue) for HypoPP muscle maintained in 2 mM K+. Our findings show that retigabine, a selective agonist of the KV7 family of potassium channels, is effective for the prevention of low-K+ induced attacks of weakness and to enhance recovery from an ongoing loss of force in mouse models of type 1 (Cacna1s) and type 2 (Scn4a) HypoPP. Substantial protection from the loss of force occurred in the low micromolar range, well within the therapeutic window for retigabine.

Pathophysiologic approach in genetic hypokalemia: An update

The pathophysiology of genetic hypokalemia is close to that of non-genetic hypokalemia. New molecular pathways physiologically involved in renal and extrarenal potassium homeostasis have been highlighted. A physiological approach to diagnosis is illustrated here, with 6 cases. Mechanisms generating and sustaining of hypokalemia are discussed. After excluding acute shift of extracellular potassium to the intracellular compartment, related to hypokalemic periodic paralysis, inappropriate kaliuresis (>40mmol/24h) concomitant to hypokalemia indicates renal potassium wasting. Clinical analysis distinguishes hypertension-associated hypokalemia, due to hypermineralocorticism or related disorders. Genetic hypertensive hypokalemia is rare. It includes familial hyperaldosteronism, Liddle syndrome, apparent mineralocorticoid excess,11beta hydroxylase deficiency and Geller syndrome. In case of normo- or hypo-tensive hypokalemia, two etiologies are to be considered: chloride depletion or salt-wasting tubulopathy. Diarrhea chlorea is a rare disease responsible for intestinal chloride depletion. Due to the severity of hypokalemic metabolic alkalosis, this disease can be misdiagnosed as pseudo-Bartter syndrome. Gitelman syndrome is the most frequent cause of genetic hypokalemia. It typically associates renal sodium and potassium wasting, hypomagnesemia, conserved chloride excretion (>40mmol/24h), and low-range calcium excretion (urinary Ca/creatinine ratio<0.20mmol/mmol). Systematic analysis of hydroelectrolytic disorder and dynamic hormonal investigation optimizes indications for and orientation of genotyping of hereditary salt-losing tubulopathy.

Muscle Channelopathies

PURPOSE OF REVIEW

This article describes the clinical features, diagnosis, pathophysiology, and management of nondystrophic myotonia and periodic paralysis.

RECENT FINDINGS

An increasing awareness exists about the genotype-phenotype overlap in skeletal muscle channelopathies, and thus genetic testing is needed to make a definitive diagnosis. Electrodiagnostic testing in channelopathies is highly specialized with significant overlap in various mutation subtypes. Randomized clinical trials have now been conducted in these disorders with expanded treatment options for patients with muscle channelopathies.

SUMMARY

Skeletal muscle channelopathies are rare heterogeneous conditions characterized by lifelong symptoms that require a comprehensive management plan that includes pharmacologic and nonpharmacologic interventions. The significant variability in biophysical features of various mutations, coupled with the difficulties of performing clinical trials in rare diseases, makes it challenging to design and implement treatment trials for muscle channelopathies.

Intravenous Iodinated Contrast Induced Thyrotoxic Periodic Paralysis: A Case Report

Thyrotoxic periodic paralysis (TPP) is an entity that has been described in the literature as a transient, symmetrical, flaccid paralysis, mainly affecting the lower limbs of patients with a current or previous history of hyperthyroidism. In most cases, Graves' disease is the cause of hyperthyroidism. Contrast and iodine-induced TPP have been described in the literature, but only one case of intravenous contrast induced TPP has been reported. We report a case of TPP following administration of intravenous contrast for a computed tomography scan of the neck prior to lymph node excision. A 35-year-old Kuwaiti male with known Graves' disease in remission until two months of his presentation, reported to the emergency room one early morning in December 2020. He sustained a fall from the stairs due to bilateral lower limb weakness, mostly proximal. The upper limbs were spared, and the patient did not experience any numbness or headache. His potassium was found to be 2.1 mmol/L and an electrocardiogram showed U waves and ST segment changes. He was initiated on 20 mEq of intravenous potassium chloride in 500 mL sodium chloride over one hour, following which his potassium approached normal and his weakness resolved. He was last known to be euthyroid in November 2019 but noted in October 2020 to be in the hyperthyroid state when thyroid function testing showed a thyroid-stimulating hormone of <0.005 (0.27-4.2 uIu/mL) and free thyroxine (T4) of 27.6 (7.8- pmol/L). In patients with known hyperthyroidism, more caution is required when iodine-containing substances are administered without proper evaluation of thyroid function.

Kir2.1 dysfunction at the sarcolemma and the sarcoplasmic reticulum causes arrhythmias in a mouse model of Andersen-Tawil syndrome type 1

Andersen-Tawil syndrome type 1 (ATS1) is associated with life-threatening arrhythmias of unknown mechanism. In this study, we generated and characterized a mouse model of ATS1 carrying the trafficking-deficient mutant Kir2.1Δ314-315 channel. The mutant mouse recapitulates the electrophysiological phenotype of ATS1, with QT prolongation exacerbated by flecainide or isoproterenol, drug-induced QRS prolongation, increased vulnerability to reentrant arrhythmias and multifocal discharges resembling catecholaminergic polymorphic ventricular tachycardia (CPVT). Kir2.1Δ314-315 cardiomyocytes display significantly reduced inward rectifier K+ and Na+ currents, depolarized resting membrane potential and prolonged action potentials. We show that, in wild-type mouse cardiomyocytes and skeletal muscle cells, Kir2.1 channels localize to sarcoplasmic reticulum (SR) microdomains, contributing to intracellular Ca2+ homeostasis. Kir2.1Δ314-315 cardiomyocytes exhibit defective SR Kir2.1 localization and function, as intact and permeabilized Kir2.1Δ314-315 cardiomyocytes display abnormal spontaneous Ca2+ release events. Overall, defective Kir2.1 channel function at the sarcolemma and the SR explain the life-threatening arrhythmias in ATS1 and its overlap with CPVT.

A dangerous food binge: a case report of hypokalemic periodic paralysis and review of current literature

BACKGROUND

Hypokalemic periodic paralysis is a rare neuromuscular genetic disorder due to defect of ion channels and subsequent function impairment. It belongs to a periodic paralyses group including hyperkalemic periodic paralysis (HEKPP), hypokalemic periodic paralysis (HOKPP) and Andersen-Tawil syndrome (ATS). Clinical presentations are mostly characterized by episodes of flaccid generalized weakness with transient hypo- or hyperkalemia.

CASE PRESENTATION

A teenage boy presented to Emergency Department (ED) for acute weakness and no story of neurological disease, during the anamnestic interview he revealed that he had a carbohydrates-rich meal the previous evening. Through a focused diagnostic work-up the most frequent and dangerous causes of paralysis were excluded, but low serum potassium concentration and positive family history for periodic paralyses raised the diagnostic suspicion of HOKPP. After the acute management in ED, he was admitted to Pediatric Department where a potassium integration was started and the patient was counselled about avoiding daily life triggers. He was discharged in few days. Unfortunately, he presented again because of a new paralytic attack due to a sugar-rich food binge the previous evening. Again, he was admitted and treated by potassium integration. This time he was strongly made aware of the risks he may face in case of poor adherence to therapy or behavioral rules. Currently, after 15 months, the boy is fine and no new flare-ups are reported.

CONCLUSION

HOKPP is a rare disease but symptoms can have a remarkable impact on patients' quality of life and can interfere with employment and educational opportunities. The treatment aims to minimize the paralysis attacks by restoring normal potassium level in order to reduce muscle excitability but it seems clear that a strong education of the patient about identification and avoidance triggering factors is essential to guarantee a benign clinical course. In our work we discuss the typical clinical presentation of these patients focusing on the key points of the diagnosis and on the challenges of therapeutic management especially in adolescence. A brief discussion of the most recent knowledge regarding this clinical condition follows.

Case report: Hyperthyroid hypokalemic periodic paralysis

Introduction and importance

HHPP is a rare type of hypokalemic PP that can occur when there is hyperthyroidism.Thyrotoxic periodic paralysis is due to increased influx of potassium into skeletal muscle cells which leads to profound hypokalemia and paralysis. Insulin and Epinephrine are also responsible for stimulating the Na–K-ATPase pumps which are over expressed during hyperthyroid state. Laboratory hypokalemia in the background of hyperthyroidism with sudden symmetric paralysis point toward the diagnosis.

Case

We present a case of 25 year old male with limb weakness for 3hours following heavy dinner.He felt weakness after waking up in the morning where he could not move his both lower limbs. He also had difficulty moving upper limbs.

Clinical findings and investigations

Examination revealed proximal muscle weakness with power of 2/5, decreased muscle tone, diminished deep tendon reflexes in all four limbs and equivocal plantar reflex bilaterally. Investigation sent were Total Leukocyte count, Hemoglobin, Renal function test, Liver Function test,Thyroid function test, Vitamin B12, Serology, ACTH, Serum calcium, Serum phosphate, Serum magnesium, Urine R/ME and Stool R/ME.

Intervention and outcome

Patient is treated with 10mEq/L/hr infusion of potassium chloride, methimazole and beta-blockers. He is stable and is in regular followup in medicine OPD.

Relevance and impact

Early diagnosis of HHPP is very essential to prevent fatal complications (cardiac and respiratory).

It can be treated by timely potassium supplementation, methimazole and beta-blockers.

Clinicians must be concerned about Hyperkalemia while supplementing Potassium in bed side.

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HHPP is a rare life-threatening complication of hyperthyroidism which is characterized by episodes of acute muscle weakness due to hypokalemia.

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Periodic paralysis (PP) is a muscle disease, characterized by episodes of painless muscle weakness. These episodes can be triggered by strenuous exercise, fasting, or consuming high-carbohydrate foods.

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Treatment cand be done by potassium supplementation until normalized serum potassium level. Patient must be kept in cardiac monitoring and serum potassium monitoring.

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Hyperthyroidism can be treated with methimazole. Patient must be kept under regular follow up in endocrinology department.

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Relapses can be prevented by treatment with radioactive iodine or surgery. Beta-blocking drugs have also been proven to reduce the frequency and severity of episodes.

Thyrotoxicosis Periodic Paralysis: A Rare Presentation of a Common Disease

We report a 31-year-old man of an Arabic ethnicity who presented to the Emergency Department (ED) with a one-night history of progressive generalized weakness followed by an inability to move all four limbs. The patient was found to have hypokalemia and hypophosphatemia. Detailed inpatient assessment revealed that the patient had undiagnosed Graves' disease with thyrotoxicosis causing electrolyte disturbances and paralysis. The patient's symptoms resolved after the correction of the electrolytes. In this case study, we report an unusual presenting symptom of paralysis of Graves' disease in a patient of Arabic ethnicity.

Conn’s Syndrome: An Unusual Cause of Periodic Paralysis

Primary hyperaldosteronism, also known as Conn’s syndrome, is characterized by an independent and excessive aldosterone production in the adrenal cortex, causing hypernatremia, arterial hypertension, and, in some cases, potentially severe hypokalemia can occur.

We report a case of a 45-year-old Caucasian woman, with a history of obesity and hypertension, who presented to the emergency room with a four-week evolution history of myalgia and ascending muscle weakness eventually resulting in tetraparesis. The initial blood analysis showed severe hypokalemia (1.5 mmol/L).

Further laboratory studies revealed an elevated plasma aldosterone level with low renin activity, and thyroid function tests were consistent with mild primary hyperthyroidism. CT scan showed a nodular lesion in the left adrenal gland. A saline suppression test confirmed that aldosterone secretion and renin activity were not suppressed. Regression of tetraparesis was noted with vigorous potassium supplementation. A laparoscopic left adrenalectomy was performed, with consequent normalization of hypokalemia, without the need for supplementation.

Periodic paralysis (PP) are a rare group of neuromuscular diseases that occur due to the affection of the ion channels of the skeletal muscle. Most cases are hereditary; nonetheless, secondary causes of PP have been reported in the literature. 

This case illustrates an unusual and severe presentation of primary hyperaldosteronism manifested by PP. The concomitant changes in thyroid function raised the possibility that we are facing the clinical influence of another rare entity: thyrotoxic hypokalemic PP. However, the resolution of hypokalemia after the removal of adrenal adenoma supported the major contribution of hyperaldosteronism.