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Channels (Austin, Tex.) Dec 2024Myotonia congenita (MC) is a rare hereditary muscle disease caused by variants in the CLCN1 gene. Currently, the correlation of phenotype-genotype is still uncertain...
Myotonia congenita (MC) is a rare hereditary muscle disease caused by variants in the CLCN1 gene. Currently, the correlation of phenotype-genotype is still uncertain between dominant-type Thomsen (TMC) and recessive-type Becker (BMC). The clinical data and auxiliary examinations of MC patients in our clinic were retrospectively collected. Electromyography was performed in 11 patients and available family members. Whole exome sequencing was conducted in all patients. The clinical and laboratory data of Chinese MC patients reported from June 2004 to December 2022 were reviewed. A total of 11 MC patients were included in the study, with a mean onset age of 12.64 ± 2.73 years. The main symptom was muscle stiffness of limbs. Warm-up phenomenon and percussion myotonia were found in all patients. Electromyogram revealed significant myotonic charges in all patients and two asymptomatic carriers, while muscle MRI and biopsy showed normal or nonspecific changes. Fourteen genetic variants including 6 novel variants were found in CLCN1. Ninety-eight Chinese patients were re-analyzed and re-summarized in this study. There were no significant differences in the demographic data, clinical characteristics, and laboratory findings between 52 TMC and 46 BMC patients. Among the 145 variants in CLCN1, some variants, including the most common variant c.892 G>A, could cause TMC in some families and BMC in others. This study expanded the clinical and genetic spectrum of Chinese patients with MC. It was difficult to distinguish between TMC and BMC only based on the clinical, laboratory, and genetic characteristics.
Topics: Humans; Myotonia Congenita; Male; Female; Chloride Channels; Child; Adolescent; Asian People; Adult; Young Adult; Electromyography; Retrospective Studies; China; Mutation; East Asian People
PubMed: 38720415
DOI: 10.1080/19336950.2024.2349823 -
Journal of Neuromuscular Diseases 2024Congenital myopathies (CMs) are rare genetic disorders for which the diagnostic yield does not typically exceed 60% . We performed deep phenotyping, histopathological...
Congenital myopathies (CMs) are rare genetic disorders for which the diagnostic yield does not typically exceed 60% . We performed deep phenotyping, histopathological studies, clinical exome and trio genome sequencing and a phenotype-driven analysis of the genomic data, that led to the molecular diagnosis in a child with CM. We identified a heterozygous variant in RYR1 in the affected child, inherited from her asymptomatic mother. Given the alignment of the clinical and histopathological phenotype with RYR1-CM, we considered the potential existence of a missing second variant in trans in the proband, but also hypothesized that the variant might be mosaic in the mother, as subsequently demonstrated. Our study is an example of how heterozygous variants inherited from asymptomatic parents are frequently dismissed. When the genotype-phenotype correlation is strong, it is recommended to consider a parental mosaicism.
Topics: Humans; Genetic Association Studies; Mosaicism; Myotonia Congenita; Phenotype; Ryanodine Receptor Calcium Release Channel; Male; Child, Preschool
PubMed: 38489196
DOI: 10.3233/JND-230216 -
Cureus Feb 2024Congenital myotonia represents a rare group of genetically inherited conditions. It can be either autosomal dominant (Thomsen) or autosomal recessive (Becker). It is...
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.
PubMed: 38469025
DOI: 10.7759/cureus.53981 -
Neurology India Jan 2024
Topics: Humans; Glycosylation; Myasthenic Syndromes, Congenital; Muscular Diseases; Myotonia Congenita; Mutation
PubMed: 38443029
DOI: 10.4103/neurol-india.Neurol-India-D-23-00582 -
Journal of Neuromuscular Diseases 2024The nondystrophic myotonias are rare muscle hyperexcitability disorders caused by gain-of-function mutations in the SCN4A gene or loss-of-function mutations in the CLCN1...
BACKGROUND
The nondystrophic myotonias are rare muscle hyperexcitability disorders caused by gain-of-function mutations in the SCN4A gene or loss-of-function mutations in the CLCN1 gene. Clinically, they are characterized by myotonia, defined as delayed muscle relaxation after voluntary contraction, which leads to symptoms of muscle stiffness, pain, fatigue, and weakness. Diagnosis is based on history and examination findings, the presence of electrical myotonia on electromyography, and genetic confirmation.
METHODS
Next-generation sequencing including the CLCN1 and SCN4A genes was performed in patients with clinical neuromuscular disorders. Electromyography, Short Exercise Test, in vivo and in vitro electrophysiology, site-directed mutagenesis and heterologous expression were collected.
RESULTS
A heterozygous point mutation (c.1775C > T, p.Thr592Ile) of muscle voltage-gated sodium channel α subunit gene (SCN4A) has been identified in five female patients over three generations, in a family with non-dystrophic myotonia. The muscle stiffness and myotonia involve mainly the face and hands, but also affect walking and running, appearing early after birth and presenting a clear cold sensitivity. Very hot temperatures, menstruation and pregnancy also exacerbate the symptoms; muscle pain and a warm-up phenomenon are variable features. Neither paralytic attacks nor post-exercise weakness has been reported. Muscle hypertrophy with cramp-like pain and increased stiffness developed during pregnancy. The symptoms were controlled with both mexiletine and acetazolamide. The Short Exercise Test after muscle cooling revealed two different patterns, with moderate absolute changes of compound muscle action potential amplitude.
CONCLUSIONS
The p.Thr592Ile mutation in the SCN4A gene identified in this Sardinian family was responsible of clinical phenotype of myotonia.
Topics: Adult; Female; Humans; Middle Aged; Electromyography; Italy; Myotonia; Myotonia Congenita; NAV1.4 Voltage-Gated Sodium Channel; Pedigree; Point Mutation
PubMed: 38427496
DOI: 10.3233/JND-230134 -
Annals of Medicine and Surgery (2012) Feb 2024Sodium channel myotonia (SCM) belongs to the group of sodium channelopathies with mutations involving gene. The main feature of sodium channel myotonia is pure myotonia...
INTRODUCTION AND IMPORTANCE
Sodium channel myotonia (SCM) belongs to the group of sodium channelopathies with mutations involving 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 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 gene indicating this case to be a sodium channelopathy.
CONCLUSION
This case limelight sodium channel myotonia with a novel Ile239Thr mutation in 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.
PubMed: 38333241
DOI: 10.1097/MS9.0000000000001673 -
World Journal of Clinical Cases Jan 2024Paramyotonia congenita (PMC) stands as a rare sodium channelopaty of skeletal muscle, initially identified by Eulenburg. The identification of PMC often relies on...
BACKGROUND
Paramyotonia congenita (PMC) stands as a rare sodium channelopaty of skeletal muscle, initially identified by Eulenburg. The identification of PMC often relies on electromyography (EMG), a diagnostic technique. The child's needle EMG unveiled trains of myotonic discharges with notably giant amplitudes, alongside irregular wave trains of myotonic discharges. This distinctive observation had not surfaced in earlier studies.
CASE SUMMARY
We report the case of a 3-year-old female child with PMC, who exhibited laryngeal stridor, muffled speech, myotonia from birth. Cold, exposure to cool water, crying, and physical activity exacerbated the myotonia, which was relieved in warmth, yet never normalized. Percussion myotonia was observable in bilateral biceps. Myotonia symptoms remained unchanged after potassium-rich food consumption like bananas. Hyperkalemic periodic paralysis was excluded. Cranial magnetic resonance imaging yielded normal results. Blood potassium remained within normal range, while creatine kinase showed slight elevation. Exome-wide genetic testing pinpointed a heterozygous mutation on chromosome SCN4A: c.3917G>A (p.G1306E). After a six-month mexiletine regimen, symptoms alleviated.
CONCLUSION
In this case revealed the two types of myotonic discharges, and had not been documented in other studies. We underscore two distinctive features: Giant-amplitude potentials and irregular waves.
PubMed: 38322461
DOI: 10.12998/wjcc.v12.i3.587 -
Heliyon Jan 2024mutations have been shown to be associated with myotonia, paramyotonia congenita, and periodic paralyses. More recently, loss-of-function variants in the gene were...
mutations have been shown to be associated with myotonia, paramyotonia congenita, and periodic paralyses. More recently, loss-of-function variants in the gene were also noted to be associated with rarer, autosomal recessive forms of congenital myasthenic syndrome and congenital myopathy. Diagnosis is challenging as the initial clinical presentation and histological features on muscle biopsies are non-specific. We report a Han Chinese patient presented with congenital myopathy with two missense variants. The patient had an antenatal history of reduced fetal movements, polyhydramnios and a very preterm birth. At birth, she was noted to have low Apgar score, respiratory distress syndrome and hypotonia. Delayed motor development was noted in early childhood. Dysmorphic features such as an elongated face, dolichocephaly and high arched palate were present. At 16 years of age, the patient developed progressive muscle weakness and was wheelchair-bound by age 20. Muscle biopsy revealed non-specific changes only. Targeted hereditary myopathy panel testing by next generation sequencing revealed two previously unreported missense variants c.1841A > T p.(Asn614Ile) and c.4420G > A p.(Ala1474Thr) in the gene. The clinical features of -related congenital myopathy and myasthenic syndrome were reviewed. This case exemplifies the utility of next generation sequencing in the diagnosis of undifferentiated muscle disease.
PubMed: 38187266
DOI: 10.1016/j.heliyon.2023.e23663 -
Biomedicines Sep 2023Myotonia congenita is a hereditary muscle disease mainly characterized by muscle hyperexcitability, which leads to a sustained burst of discharges that correlates with... (Review)
Review
Myotonia congenita is a hereditary muscle disease mainly characterized by muscle hyperexcitability, which leads to a sustained burst of discharges that correlates with the magnitude and duration of involuntary aftercontractions, muscle stiffness, and hypertrophy. Mutations in the chloride voltage-gated channel 1 () gene that encodes the skeletal muscle chloride channel (ClC-1) are responsible for this disease, which is commonly known as myotonic chloride channelopathy. The biophysical properties of the mutated channel have been explored and analyzed through in vitro approaches, providing important clues to the general function/dysfunction of the wild-type and mutated channels. After an exhaustive search for mutations, we report in this review more than 350 different mutations identified in the literature. We start discussing the physiological role of the ClC-1 channel in skeletal muscle functioning. Then, using the reported functional effects of the naturally occurring mutations, we describe the biophysical and structural characteristics of the ClC-1 channel to update the knowledge of the function of each of the ClC-1 helices, and finally, we attempt to point out some patterns regarding the effects of mutations in the different helices and loops of the protein.
PubMed: 37892996
DOI: 10.3390/biomedicines11102622 -
Psychiatria Danubina Oct 2023
Topics: Humans; Myotonia Congenita
PubMed: 37800267
DOI: No ID Found