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Elaraby NM, Ahmed HA, Dawoud H, Ashaat NA, Azmy A, Galal ER, Elhusseny Y, Awady HE, Metwally AM, Ashaat EA. Clinical and molecular characterization of myotonia congenita using whole-exome sequencing in Egyptian patients. Mol Biol Rep 2024; 51:766. [PMID: 38877370 DOI: 10.1007/s11033-024-09646-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2024] [Accepted: 05/16/2024] [Indexed: 06/16/2024]
Abstract
BACKGROUND Myotonia Congenita (MC) is a rare disease classified into two major forms; Thomsen and Becker disease caused by mutations in the CLCN1 gene, which affects muscle excitability and encodes voltage-gated chloride channels (CLC-1). While, there are no data regarding the clinical and molecular characterization of myotonia in Egyptian patients. METHODS Herein, we report seven Egyptian MC patients from six unrelated families. Following the clinical diagnosis, whole-exome sequencing (WES) was performed for genetic diagnosis. Various in silico prediction tools were utilized to interpret variant pathogenicity. The candidate variants were then validated using Sanger sequencing technique. RESULTS In total, seven cases were recruited. The ages at the examination were ranged from eight months to nineteen years. Clinical manifestations included warm-up phenomenon, hand grip, and percussion myotonia. Electromyography was performed in all patients and revealed myotonic discharges. Molecular genetic analysis revealed five different variants. Of them, we identified two novel variants in the CLCN1 gene ( c.1583G > C; p.Gly528Ala and c.2203_2216del;p.Thr735ValfsTer57) and three known variants in the CLCN1 and SCN4A gene. According to in silico tools, the identified novel variants were predicted to have deleterious effects. CONCLUSIONS As the first study to apply WES among Egyptian MC patients, our findings reported two novel heterozygous variants that expand the CLCN1 mutational spectrum for MC diagnosis. These results further confirm that genetic testing is essential for early diagnosis of MC, which affects follow-up treatment and prognostic assessment in clinical practice.
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Affiliation(s)
- Nesma M Elaraby
- Medical Molecular Genetics Department, Human Genetics and Genome Research Institute, National Research Centre, Dokki, Cairo, Egypt.
| | - Hoda A Ahmed
- Medical Molecular Genetics Department, Human Genetics and Genome Research Institute, National Research Centre, Dokki, Cairo, Egypt
| | - Heba Dawoud
- Pediatric Department, Tanta University, Gharbia, Egypt
| | - Neveen A Ashaat
- Professor of Human Genetics, Ain Shams University, Cairo, Egypt
| | - Ashraf Azmy
- Child Health Department, Medical Research and Clinical Studies Institute, National Research Centre, Dokki, Cairo, Egypt
| | - Eman Reda Galal
- Biochemistry and Molecular Biology Department, Faculty of Pharmacy (Girls), Al-Azhar University, Cairo, Egypt
| | - Yasmine Elhusseny
- Lecturer of Medical Biochemistry and Molecular Biology, School of Medicine, Newgiza University, Giza, Egypt
| | - Heba El Awady
- Pediatric Department, Fayoum University Hospitals, Fayoum, Egypt
| | - Ammal M Metwally
- Community Medicine Research Department/Medical Research, Clinical Studies Institute/National Research Centre (Affiliation ID: 60014618), Dokki, Cairo, Egypt
| | - Engy A Ashaat
- Clinical Genetics Department, Human Genetics and Genome Research Institute, National Research Centre, Cairo, Egypt
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Sriretnakumar V, Harripaul R, Kennedy JL, So J. When rare meets common: Treatable genetic diseases are enriched in the general psychiatric population. Am J Med Genet A 2024:e63609. [PMID: 38532509 DOI: 10.1002/ajmg.a.63609] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Revised: 03/06/2024] [Accepted: 03/13/2024] [Indexed: 03/28/2024]
Abstract
Mental illnesses are one of the biggest contributors to the global disease burden. Despite the increased recognition, diagnosis and ongoing research of mental health disorders, the etiology and underlying molecular mechanisms of these disorders are yet to be fully elucidated. Moreover, despite many treatment options available, a large subset of the psychiatric patient population is nonresponsive to standard medications and therapies. There has not been a comprehensive study to date examining the burden and impact of treatable genetic disorders (TGDs) that can present with neuropsychiatric features in psychiatric patient populations. In this study, we test the hypothesis that TGDs that present with psychiatric symptoms are more prevalent within psychiatric patient populations compared to the general population by performing targeted next-generation sequencing of 129 genes associated with 108 TGDs in a cohort of 2301 psychiatric patients. In total, 48 putative affected and 180 putative carriers for TGDs were identified, with known or likely pathogenic variants in 79 genes. Despite screening for only 108 genetic disorders, this study showed a two-fold (2.09%) enrichment for genetic disorders within the psychiatric population relative to the estimated 1% cumulative prevalence of all single gene disorders globally. This strongly suggests that the prevalence of these, and most likely all, genetic diseases is greatly underestimated in psychiatric populations. Increasing awareness and ensuring accurate diagnosis of TGDs will open new avenues to targeted treatment for a subset of psychiatric patients.
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Affiliation(s)
- Venuja Sriretnakumar
- Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, Toronto, Canada
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada
| | - Ricardo Harripaul
- Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, Toronto, Canada
- Institute of Medical Science, University of Toronto, Toronto, Canada
| | - James L Kennedy
- Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, Toronto, Canada
- Department of Psychiatry, University of Toronto, Toronto, Canada
| | - Joyce So
- Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, Toronto, Canada
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada
- Department of Psychiatry, University of Toronto, Toronto, Canada
- Department of Medicine, University of Toronto, Toronto, Canada
- Division of Medical Genetics, Departments of Medicine and Pediatrics, University of California, San Francisco, California, USA
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Suphatsathienkul P, Sakpichaisakul K, Wechapinan T, Trachoo O, Virawan S, Wanitphakdeedecha R. Successful Treatment of Schwartz-Jampel Syndrome with Botulinum Toxin Type A. Dermatol Ther (Heidelb) 2024; 14:545-556. [PMID: 38285320 PMCID: PMC10890988 DOI: 10.1007/s13555-023-01088-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2023] [Accepted: 12/13/2023] [Indexed: 01/30/2024] Open
Abstract
Schwartz-Jampel syndrome (SJS) is a rare autosomal recessive disorder characterized by typical facial dysmorphism, generalized muscle stiffness, joint contracture, and skeletal abnormalities. This condition is caused by mutations in the heparan sulfate proteoglycan 2 (HSPG2) gene, which encodes perlecan, a component of the basement membrane. The management of patients with SJS primarily aims to alleviate symptoms related to muscle stiffness. In this report, we describe a male patient with SJS type 1A. Trio whole-exome sequencing identified a pathogenic mutation (NM_001291860.1: c.10897C>T; p.Arg3633Ter) and variants of unknown significance (NM_001291860.2: c.413+10G>T). The patient experienced difficulty in opening his eyes and mouth, which significantly limited his daily activities. Botulinum toxin A injection was administered and demonstrated significant clinical improvement after the treatment.
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Affiliation(s)
- Panittra Suphatsathienkul
- Department of Dermatology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand
| | - Kullasate Sakpichaisakul
- Division of Neurology, Department of Pediatrics, Ministry of Public Health, Queen Sirikit National Institute of Child Health, Bangkok, Thailand
- College of Medicine, Rangsit University, Bangkok, Thailand
| | - Thanin Wechapinan
- Division of Neurology, Department of Pediatrics, Ministry of Public Health, Queen Sirikit National Institute of Child Health, Bangkok, Thailand
- Ministry of Public Health, Neurological Institute of Thailand, Bangkok, Thailand
| | - Objoon Trachoo
- Centre for Medical Genomics, Faculty of Medicine Ramathibodi Hospital, Mahidol University, Bangkok, Thailand
- Department of Medicine, Faculty of Medicine Ramathibodi Hospital, Mahidol University, Bangkok, Thailand
| | - Sorawit Virawan
- Division of Neurology, Department of Pediatrics, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand
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Yadav J, Barnwal R, Kumar Mandal S, Prajapati B. Acetazolamide-responsive myotonia with a novel Ile239Thr mutation in SCN4A gene: a case report. Ann Med Surg (Lond) 2024; 86:1191-1195. [PMID: 38333241 PMCID: PMC10849450 DOI: 10.1097/ms9.0000000000001673] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Accepted: 12/20/2023] [Indexed: 02/10/2024] Open
Abstract
Introduction and importance Sodium channel myotonia (SCM) belongs to the group of sodium channelopathies with mutations involving SCN4A gene. The main feature of sodium channel myotonia is pure myotonia without episodes of weakness or paralysis. One of the sodium channel myotonia has been classified as acetazolamide-responsive myotonia because of the effectiveness of acetazolamide as an antimyotonic drug. Case presentation The child presented with generalized muscle hypertrophy and stiffness involving arms, thighs, calves, chest, and back muscles with unusually prominent trapezius muscle. The parents described the warm-up phenomenon as an improvement in stiffness as the day passes and with repetitive action. Percussion myotonia was illustrated in the thenar eminence and trapezius muscle. Characteristic 'dive-bomber' sound was present in electromyography, and whole-exome sequencing revealed a novel Ile239Thr mutation in the SCN4A gene. Acetazolamide was prescribed for the condition, and regular follow-up shows an excellent clinical response. Clinical discussion This case presents a pure myotonic phenotype without episodes of weakness or paralysis. Generalized myotonia with muscle hypertrophy and demonstrating warm-up phenomenon resembles myotonia congenita (a chloride channelopathy). However, genetic analysis revealed a novel Ile239Thr mutation involving SCN4A gene indicating this case to be a sodium channelopathy. Conclusion This case limelight sodium channel myotonia with a novel Ile239Thr mutation in SCN4A gene that phenotypically resembles myotonia congenita but genetically belongs to sodium channelopathy highlighting the poor correlation between genotypes and phenotypes in non-dystrophic myotonia. Acetazolamide can be a safe and cost-effective antimyotonic drug in sodium channel myotonia.
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Das P, Panigrahi D. Autosomal Recessive Myotonia Congenita in an Adolescent Boy With Novel Mutation: A Case Report With Discussion on Management. Cureus 2024; 16:e53981. [PMID: 38469025 PMCID: PMC10927349 DOI: 10.7759/cureus.53981] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/10/2024] [Indexed: 03/13/2024] Open
Abstract
Congenital myotonia represents a rare group of genetically inherited conditions. It can be either autosomal dominant (Thomsen) or autosomal recessive (Becker). It is characterized by muscular hypertrophy, proximal weakness, and myotonia, or impaired relaxation after contraction. These are due to mutations in the CLC1 gene. A 14-year-old male child presented with complaints of gradually progressive weakness for five years. Weakness was more pronounced in the proximal muscle groups. The weakness worsened after rest and improved with activity. This led to absenteeism and affected his school performance. Clinical examination showed generalized muscular hypertrophy with pronounced hypertrophy of the calf muscles. A neurological examination showed significant myotonia and impaired relaxation after making a fist. The diagnosis of myotonia was confirmed by electromyography, which produced a dive-bomber sound on insertion. Next-generation sequencing revealed a homozygous eight-base pair insertion in exon 19 of the CLCN1 gene. This mutation has not been reported in the existing literature for myotonia congenita. The child was started on mexiletine and improved significantly. Presently, the patient is on regular medications and doing well on follow-up. Though rare, congenital myotonia is an important cause of neuromuscular weakness. It can be easily diagnosed with a thorough clinical examination and routine testing for myotonia in all children with weakness. The treatment is relatively simple and can give the patient significant relief. Myotonia can be easily diagnosed clinically, and pharmacotherapy and proper monitoring can remarkably improve patients' quality of life.
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Affiliation(s)
- Palash Das
- Pediatric Medicine, Kalinga Institute of Medical Sciences, Bhubaneshwar, IND
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Altamura C, Saltarella I, Campanale C, Laghetti P, Desaphy JF. Drug repurposing in skeletal muscle ion channelopathies. Curr Opin Pharmacol 2023; 68:102329. [PMID: 36512979 DOI: 10.1016/j.coph.2022.102329] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Revised: 10/26/2022] [Accepted: 11/02/2022] [Indexed: 12/14/2022]
Abstract
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.
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Affiliation(s)
- Concetta Altamura
- Section of Pharmacology, Department of Precision and Regenerative Medicine, School of Medicine, University of Bari Aldo Moro, Piazza Giulo Cesare, 70124, Bari, Italy
| | - Ilaria Saltarella
- Section of Pharmacology, Department of Precision and Regenerative Medicine, School of Medicine, University of Bari Aldo Moro, Piazza Giulo Cesare, 70124, Bari, Italy
| | - Carmen Campanale
- Section of Pharmacology, Department of Precision and Regenerative Medicine, School of Medicine, University of Bari Aldo Moro, Piazza Giulo Cesare, 70124, Bari, Italy
| | - Paola Laghetti
- Section of Pharmacology, Department of Precision and Regenerative Medicine, School of Medicine, University of Bari Aldo Moro, Piazza Giulo Cesare, 70124, Bari, Italy
| | - Jean-François Desaphy
- Section of Pharmacology, Department of Precision and Regenerative Medicine, School of Medicine, University of Bari Aldo Moro, Piazza Giulo Cesare, 70124, Bari, Italy.
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Quiñonez M, DiFranco M, Wu F, Cannon SC. Retigabine suppresses loss of force in mouse models of hypokalaemic periodic paralysis. Brain 2023; 146:1554-1560. [PMID: 36718088 PMCID: PMC10115351 DOI: 10.1093/brain/awac441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2022] [Revised: 10/18/2022] [Accepted: 11/12/2022] [Indexed: 02/01/2023] Open
Abstract
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.
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Affiliation(s)
- Marbella Quiñonez
- Department of Physiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Marino DiFranco
- Department of Physiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Fenfen Wu
- Department of Physiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Stephen C Cannon
- Department of Physiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA.,Department of Neurology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
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Zhang Z, Xiao B. Case report: SCN4A p.R1135H gene variant in combination with thyrotoxicosis causing hypokalemic periodic paralysis. Front Neurol 2023; 13:1078784. [PMID: 36733446 PMCID: PMC9886676 DOI: 10.3389/fneur.2022.1078784] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Accepted: 12/28/2022] [Indexed: 01/18/2023] Open
Abstract
Hypokalemic periodic paralysis (HPP) is a heterogeneous group of diseases characterized by intermittent episodes of delayed paralysis of skeletal muscle with episodes of hypokalemia, caused by variants in CACNA1S or SCN4A genes, or secondary to thyrotoxicosis, Sjogren syndrome, primary aldosteronism, etc. HPP may be the only presentation in Andersen-Tawil syndrome in which the majority of cases are caused by pathogenic variants in the KCNJ2 gene. We present a case of a 29-year-old male with hypokalemic periodic paralysis. The patient began to experience recurrent weakness of the extremities at the age of 26, which was effectively treated with potassium supplementation. He had recently developed dry mouth, palpitations, weight loss, and even dyspnea, with a serum potassium level as low as 1.59 mmol/L. The results of auxiliary examinations showed Graves' disease, and genetic testing indicated a missense variant, NM_000334.4 (SCN4A):c.3404G>A (p.R1135H). He did not experience periodic paralysis during follow-up after lifestyle guidance and treatment of thyrotoxicosis with radioactive iodine. It is a rare case of SCN4A p.R1135H gene variant combined with hyperthyroidism resulting in HPP with respiratory muscle paralysis to raise awareness of the disease and avoid misdiagnosis and missed diagnosis.
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De Bellis M, Boccanegra B, Cerchiara AG, Imbrici P, De Luca A. Blockers of Skeletal Muscle Na v1.4 Channels: From Therapy of Myotonic Syndrome to Molecular Determinants of Pharmacological Action and Back. Int J Mol Sci 2023; 24:ijms24010857. [PMID: 36614292 PMCID: PMC9821513 DOI: 10.3390/ijms24010857] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Revised: 12/28/2022] [Accepted: 12/30/2022] [Indexed: 01/05/2023] Open
Abstract
The voltage-gated sodium channels represent an important target for drug discovery since a large number of physiological processes are regulated by these channels. In several excitability disorders, including epilepsy, cardiac arrhythmias, chronic pain, and non-dystrophic myotonia, blockers of voltage-gated sodium channels are clinically used. Myotonia is a skeletal muscle condition characterized by the over-excitability of the sarcolemma, resulting in delayed relaxation after contraction and muscle stiffness. The therapeutic management of this disorder relies on mexiletine and other sodium channel blockers, which are not selective for the Nav1.4 skeletal muscle sodium channel isoform. Hence, the importance of deepening the knowledge of molecular requirements for developing more potent and use-dependent drugs acting on Nav1.4. Here, we review the available treatment options for non-dystrophic myotonia and the structure-activity relationship studies performed in our laboratory with a focus on new compounds with potential antimyotonic activity.
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Trivedi JR. Muscle Channelopathies. Continuum (Minneap Minn) 2022; 28:1778-1799. [PMID: 36537980 DOI: 10.1212/con.0000000000001183] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
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.
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Characterization in Inhibitory Effectiveness of Carbamazepine in Voltage-Gated Na + and Erg-Mediated K + Currents in a Mouse Neural Crest-Derived (Neuro-2a) Cell Line. Int J Mol Sci 2022; 23:ijms23147892. [PMID: 35887240 PMCID: PMC9321339 DOI: 10.3390/ijms23147892] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Revised: 07/15/2022] [Accepted: 07/15/2022] [Indexed: 12/18/2022] Open
Abstract
Carbamazepine (CBZ, Tegretol®) is an anticonvulsant used in the treatment of epilepsy and neuropathic pain; however, several unwanted effects of this drug have been noticed. Therefore, the regulatory actions of CBZ on ionic currents in electrically excitable cells need to be reappraised, although its efficacy in suppressing voltage-gated Na+ current (INa) has been disclosed. This study was undertaken to explore the modifications produced by CBZ on ionic currents (e.g., INa and erg-mediated K+ current [IK(erg)]) measured from Neuro-2a (N2a) cells. In these cells, we found that this drug differentially suppressed the peak (transient, INa(T)) and sustained (late, INa(L)) components of INa in a concentration-dependent manner with effective IC50 of 56 and 18 μM, respectively. The overall current–voltage relationship of INa(T) with or without the addition of CBZ remained unchanged; however, the strength (i.e., ∆area) in the window component of INa (INa(W)) evoked by the short ascending ramp pulse (Vramp) was overly lessened in the CBZ presence. Tefluthrin (Tef), a synthetic pyrethroid, known to stimulate INa, augmented the strength of the voltage-dependent hysteresis (Hys(V)) of persistent INa (INa(P)) in response to the isosceles-triangular Vramp; moreover, further application of CBZ attenuated Tef-mediated accentuation of INa(P)’s Hys(V). With a two-step voltage protocol, the recovery of INa(T) inactivation seen in Neuro-2a cells became progressively slowed by adding CBZ; however, the cumulative inhibition of INa(T) evoked by pulse train stimulation was enhanced during exposure to this drug. Neuro-2a-cell exposure to CBZ (100 μM), the magnitude of erg-mediated K+ current measured throughout the entire voltage-clamp steps applied was mildly inhibited. The docking results regarding the interaction of CBZ and voltage-gate Na+ (NaV) channel predicted the ability of CBZ to bind to some amino-acid residues in NaV due to the existence of a hydrogen bond or hydrophobic contact. It is conceivable from the current investigations that the INa (INa(T), INa(L), INa(W), and INa(P)) residing in Neuro-2a cells are susceptible to being suppressed by CBZ, and that its block on INa(L) is larger than that on INa(T). Collectively, the magnitude and gating of NaV channels produced by the CBZ presence might have an impact on its anticonvulsant and analgesic effects occurring in vivo.
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Gaik C, Arndt C. [Rhabdomyolysis - the chamaeleon of the intensive care unit]. Anasthesiol Intensivmed Notfallmed Schmerzther 2022; 57:502-507. [PMID: 35896388 DOI: 10.1055/a-1872-9968] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
Myotonia congenita Thomsen is a rare genetic disease caused by mutations in the skeletal muscle chloride channel gene (CLCN1). Although this channelopathy may cause disabling muscle symptoms, patient's daily routine can be almost inconspicuous. Nevertheless, during illness or acute diseases this neuromuscular disease may worsen and get clinically apparent up to severe rhabdomyolysis. Within this case report we describe and discuss the treatment of a patient with Myotonia congenita Thomsen treated at our hospital's intensive care unit. Rhabdomyolysis with acute renal failure and necessity of dialysis during the ICU stay was attributed to the initial reason for emergency hospitalization - an aortic dissection. Nevertheless, in this case the patient's myotonia caused rhabdomyolysis and initially led us on a wrong path. Diagnosis of the real cause of rhabdomyolysis is often difficult, although an early and adequate therapy may prevent complications. This case report demonstrates the importance of a thorough anamnesis with all aspects of the patient's history.
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Chapman AM, Schurer M, Weijers L, Omar A, Lee H, Weidenfeller AZ, Ellis C, Sonecha S, Schneider-Gold C. Improving the understanding of how patients with non-dystrophic myotonia are selected for myotonia treatment with mexiletine (NaMuscla): outcomes of treatment impact using a European Delphi panel. BMC Neurol 2021; 21:467. [PMID: 34852780 PMCID: PMC8633892 DOI: 10.1186/s12883-021-02491-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Accepted: 11/10/2021] [Indexed: 11/17/2022] Open
Abstract
Background Non-dystrophic myotonias (NDMs) comprise muscle chloride and sodium channelopathies due to genetic defects of the CLCN1- and SCN4A-channels. No licensed antimyotonic treatment has been available until approval of mexiletine (NaMuscla®) for adult patients by the EMA in December 2018. This Delphi panel aimed to understand how outcomes of the pivotal phase III Mexiletine study (MYOMEX) translate to real world practice and investigate health resource use, quality of life and the natural history of NDM to support economic modelling and facilitate patient access. Methods Nine clinical experts in treating NDM took part in a two-round Delphi panel. Their knowledge of NDM and previous use of mexiletine as an off-label treatment prior to NaMuscla’s approval ensured they could provide both qualitative context and quantitative estimates to support economic modelling comparing mexiletine (NaMuscla) to best supportive care. Consensus in four key areas was sought: healthcare resource utilization (HRU), treatment with mexiletine (NaMuscla), patient quality of life (QoL), and the natural history of disease. Concept questions were also asked, considering perceptions on the feasibility of mapping the validated Individualized Neuromuscular Quality of Life (INQoL) instrument to the generic EQ-5D™, and the potential impact on caregiver QoL. Results Consensus was achieved for key questions including the average long-term dosage of mexiletine (NaMuscla) in practice, the criteria for eligibility of myotonia treatment, the clinical importance of QoL outcomes in MYOMEX, the higher proportion of patients with increased QoL, and the reduction in the need for mental health resources for patients receiving mexiletine (NaMuscla). While consensus was not achieved for other questions, the results demonstrated that most experts felt mexiletine (NaMuscla) reduced the need for HRU and was expected to improve QoL. The QoL mapping exercise suggested that it is feasible to map domains of INQoL to EQ-5D. Points of interest for future research were identified, including that mexiletine (NaMuscla) may slow the annual decrease in QoL of patients over their lifetime, and a significant negative impact on QoL for some caregivers. Conclusions This project successfully provided data from an informed group of clinical experts, complementing the currently available clinical trial data for mexiletine (NaMuscla) to support patient access decisions. Supplementary Information The online version contains supplementary material available at 10.1186/s12883-021-02491-3.
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Affiliation(s)
| | | | | | - Amer Omar
- Lupin Atlantis Holdings SA, Zug, Switzerland
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Nicole S, Lory P. New Challenges Resulting From the Loss of Function of Na v1.4 in Neuromuscular Diseases. Front Pharmacol 2021; 12:751095. [PMID: 34671263 PMCID: PMC8521073 DOI: 10.3389/fphar.2021.751095] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2021] [Accepted: 09/16/2021] [Indexed: 11/13/2022] Open
Abstract
The voltage-gated sodium channel Nav1.4 is a major actor in the excitability of skeletal myofibers, driving the muscle force in response to nerve stimulation. Supporting further this key role, mutations in SCN4A, the gene encoding the pore-forming α subunit of Nav1.4, are responsible for a clinical spectrum of human diseases ranging from muscle stiffness (sodium channel myotonia, SCM) to muscle weakness. For years, only dominantly-inherited diseases resulting from Nav1.4 gain of function (GoF) were known, i.e., non-dystrophic myotonia (delayed muscle relaxation due to myofiber hyperexcitability), paramyotonia congenita and hyperkalemic or hypokalemic periodic paralyses (episodic flaccid muscle weakness due to transient myofiber hypoexcitability). These last 5 years, SCN4A mutations inducing Nav1.4 loss of function (LoF) were identified as the cause of dominantly and recessively-inherited disorders with muscle weakness: periodic paralyses with hypokalemic attacks, congenital myasthenic syndromes and congenital myopathies. We propose to name this clinical spectrum sodium channel weakness (SCW) as the mirror of SCM. Nav1.4 LoF as a cause of permanent muscle weakness was quite unexpected as the Na+ current density in the sarcolemma is large, securing the ability to generate and propagate muscle action potentials. The properties of SCN4A LoF mutations are well documented at the channel level in cellular electrophysiological studies However, much less is known about the functional consequences of Nav1.4 LoF in skeletal myofibers with no available pertinent cell or animal models. Regarding the therapeutic issues for Nav1.4 channelopathies, former efforts were aimed at developing subtype-selective Nav channel antagonists to block myofiber hyperexcitability. Non-selective, Nav channel blockers are clinically efficient in SCM and paramyotonia congenita, whereas patient education and carbonic anhydrase inhibitors are helpful to prevent attacks in periodic paralyses. Developing therapeutic tools able to counteract Nav1.4 LoF in skeletal muscles is then a new challenge in the field of Nav channelopathies. Here, we review the current knowledge regarding Nav1.4 LoF and discuss the possible therapeutic strategies to be developed in order to improve muscle force in SCW.
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Affiliation(s)
- Sophie Nicole
- Institut de Génomique Fonctionnelle (IGF), Université de Montpellier, CNRS, INSERM, Montpellier, France.,LabEx 'Ion Channel Science and Therapeutics (ICST), Montpellier, France
| | - Philippe Lory
- Institut de Génomique Fonctionnelle (IGF), Université de Montpellier, CNRS, INSERM, Montpellier, France.,LabEx 'Ion Channel Science and Therapeutics (ICST), Montpellier, France
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15
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Milani G, Cavalluzzi MM, Altamura C, Santoro A, Perrone M, Muraglia M, Colabufo NA, Corbo F, Casalino E, Franchini C, Pisano I, Desaphy J, Carrieri A, Carocci A, Lentini G. Bioisosteric Modification of To042: Synthesis and Evaluation of Promising Use-Dependent Inhibitors of Voltage-Gated Sodium Channels. ChemMedChem 2021; 16:3588-3599. [PMID: 34519427 PMCID: PMC9293070 DOI: 10.1002/cmdc.202100496] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2021] [Revised: 09/01/2021] [Indexed: 11/07/2022]
Abstract
Three analogues of To042, a tocainide-related lead compound recently reported for the treatment of myotonia, were synthesized and evaluated in vitro as skeletal muscle sodium channel blockers possibly endowed with enhanced use-dependent behavior. Patch-clamp experiments on hNav1.4 expressed in HEK293 cells showed that N-[(naphthalen-1-yl)methyl]-4-[(2,6-dimethyl)phenoxy]butan-2-amine, the aryloxyalkyl bioisostere of To042, exerted a higher use-dependent block than To042 thus being able to preferentially block the channels in over-excited membranes while preserving healthy tissue function. It also showed the lowest active transport across BBB according to the results of P-glycoprotein (P-gp) interacting activity evaluation and the highest cytoprotective effect on HeLa cells. Quantum mechanical calculations and dockings gave insights on the most probable conformation of the aryloxyalkyl bioisostere of To042 in solution and the target residues involved in the binding, respectively. Both approaches indicated the conformations that might be adopted in both the unbound and bound state of the ligand. Overall, N-[(naphthalen-1-yl)methyl]-4-[(2,6-dimethyl)phenoxy]butan-2-amine exhibits an interesting toxico-pharmacological profile and deserves further investigation.
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Affiliation(s)
- Gualtiero Milani
- Department of Pharmacy – Pharmaceutical SciencesUniversity of Bari Aldo MoroVia E. Orabona 470125BariItaly
| | - Maria Maddalena Cavalluzzi
- Department of Pharmacy – Pharmaceutical SciencesUniversity of Bari Aldo MoroVia E. Orabona 470125BariItaly
| | - Concetta Altamura
- Department of Biomedical Sciences and Human OncologySchool of MedicineUniversity of Bari Aldo Moro PoliclinicoPiazza Giulio Cesare70124BariItaly
| | - Antonella Santoro
- Department of Bioscience, Biotechnology and BiopharmaceuticsUniversity of Bari Aldo MoroVia Orabona 470125BariItaly
| | - Mariagrazia Perrone
- Department of Pharmacy – Pharmaceutical SciencesUniversity of Bari Aldo MoroVia E. Orabona 470125BariItaly
| | - Marilena Muraglia
- Department of Pharmacy – Pharmaceutical SciencesUniversity of Bari Aldo MoroVia E. Orabona 470125BariItaly
| | - Nicola Antonio Colabufo
- Department of Pharmacy – Pharmaceutical SciencesUniversity of Bari Aldo MoroVia E. Orabona 470125BariItaly
| | - Filomena Corbo
- Department of Pharmacy – Pharmaceutical SciencesUniversity of Bari Aldo MoroVia E. Orabona 470125BariItaly
| | - Elisabetta Casalino
- Department of Veterinary MedicineUniversity of Bari Aldo MoroVia E. Orabona 470125BariItaly
| | - Carlo Franchini
- Department of Pharmacy – Pharmaceutical SciencesUniversity of Bari Aldo MoroVia E. Orabona 470125BariItaly
| | - Isabella Pisano
- Department of Bioscience, Biotechnology and BiopharmaceuticsUniversity of Bari Aldo MoroVia Orabona 470125BariItaly
| | - Jean‐François Desaphy
- Department of Biomedical Sciences and Human OncologySchool of MedicineUniversity of Bari Aldo Moro PoliclinicoPiazza Giulio Cesare70124BariItaly
| | - Antonio Carrieri
- Department of Pharmacy – Pharmaceutical SciencesUniversity of Bari Aldo MoroVia E. Orabona 470125BariItaly
| | - Alessia Carocci
- Department of Pharmacy – Pharmaceutical SciencesUniversity of Bari Aldo MoroVia E. Orabona 470125BariItaly
| | - Giovanni Lentini
- Department of Pharmacy – Pharmaceutical SciencesUniversity of Bari Aldo MoroVia E. Orabona 470125BariItaly
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Matthews E, Holmes S, Fialho D. Skeletal muscle channelopathies: a guide to diagnosis and management. Pract Neurol 2021; 21:196-204. [PMID: 33563766 DOI: 10.1136/practneurol-2020-002576] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/19/2020] [Indexed: 12/17/2022]
Abstract
Skeletal muscle channelopathies are a group of rare episodic genetic disorders comprising the periodic paralyses and the non-dystrophic myotonias. They may cause significant morbidity, limit vocational opportunities, be socially embarrassing, and sometimes are associated with sudden cardiac death. The diagnosis is often hampered by symptoms that patients may find difficult to describe, a normal examination in the absence of symptoms, and the need to interpret numerous tests that may be normal or abnormal. However, the symptoms respond very well to holistic management and pharmacological treatment, with great benefit to quality of life. Here, we review when to suspect a muscle channelopathy, how to investigate a possible case and the options for therapy once a diagnosis is made.
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Affiliation(s)
- Emma Matthews
- Atkinson-Morley Neuromuscular Centre, St George's University Hospitals NHS Foundation Trust, London, UK
- Department of Neuromuscular Diseases, UCL, Institute of Neurology, London, UK
| | - Sarah Holmes
- Queen Square Centre for Neuromuscular Diseases, National Hospital for Neurology and Neurosurgery, London, UK
| | - Doreen Fialho
- Department of Neuromuscular Diseases, UCL, Institute of Neurology, London, UK
- Queen Square Centre for Neuromuscular Diseases, National Hospital for Neurology and Neurosurgery, London, UK
- Department of Clinical Neurophysiology, King's College Hospital NHS Foundation Trust, London, UK
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Danti FR, Invernizzi F, Moroni I, Garavaglia B, Nardocci N, Zorzi G. Pediatric Paroxysmal Exercise-Induced Neurological Symptoms: Clinical Spectrum and Diagnostic Algorithm. Front Neurol 2021; 12:658178. [PMID: 34140924 PMCID: PMC8203909 DOI: 10.3389/fneur.2021.658178] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Accepted: 04/21/2021] [Indexed: 12/18/2022] Open
Abstract
Paroxysmal exercise-induced neurological symptoms (PENS) encompass a wide spectrum of clinical phenomena commonly presenting during childhood and characteristically elicited by physical exercise. Interestingly, few shared pathogenetic mechanisms have been identified beyond the well-known entity of paroxysmal exercise-induced dyskinesia, PENS could be part of more complex phenotypes including neuromuscular, neurodegenerative, and neurometabolic disease, epilepsies, and psychogenetic disorders. The wide and partially overlapping phenotypes and the genetic heterogeneity make the differential diagnosis frequently difficult and delayed; however, since some of these disorders may be treatable, a prompt diagnosis is mandatory. Therefore, an accurate characterization of these symptoms is pivotal for orienting more targeted biochemical, radiological, neurophysiological, and genetic investigations and finally treatment. In this article, we review the clinical, genetic, pathophysiologic, and therapeutic landscape of paroxysmal exercise induced neurological symptoms, focusing on phenomenology and differential diagnosis.
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Affiliation(s)
- Federica Rachele Danti
- Unit of Child Neurology, Department of Pediatric Neuroscience, Fondazione Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Istituto Neurologico Carlo Besta, Milan, Italy
| | - Federica Invernizzi
- Unit of Medical Genetics and Neurogenetics, Fondazione Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Istituto Neurologico C. Besta, Milan, Italy
| | - Isabella Moroni
- Unit of Child Neurology, Department of Pediatric Neuroscience, Fondazione Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Istituto Neurologico Carlo Besta, Milan, Italy
| | - Barbara Garavaglia
- Unit of Medical Genetics and Neurogenetics, Fondazione Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Istituto Neurologico C. Besta, Milan, Italy
| | - Nardo Nardocci
- Unit of Child Neurology, Department of Pediatric Neuroscience, Fondazione Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Istituto Neurologico Carlo Besta, Milan, Italy
| | - Giovanna Zorzi
- Unit of Child Neurology, Department of Pediatric Neuroscience, Fondazione Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Istituto Neurologico Carlo Besta, Milan, Italy
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