Clinical score for early diagnosis of myotonic dystrophy type 2.

INTRODUCTION: Myotonic dystrophy type 2 (DM2) is a rare, multisystemic, autosomal dominant disease with highly variable clinical presentation. DM2 is considered to be highly underdiagnosed. OBJECTIVE: The aim of this study was to determine which symptoms, signs, and diagnostic findings in patients referred to neurological outpatient units are the most indicative to arouse suspicion of DM2. We tried to make a useful and easy-to-administer clinical scoring system for early diagnosis of DM2-DM2 early diagnosis score (DM2-EDS). PATIENTS AND METHODS: Two hundred ninety-one patients with a clinical suspicion of DM2 were included: 69 were genetically confirmed to have DM2, and 222 patients were DM2 negative. Relevant history, neurological, and paraclinical data were obtained from the electronic medical records. RESULTS: The following parameters appeared as significant predictors of DM2 diagnosis: cataracts (beta = 0.410, p < 0.001), myotonia on needle EMG (beta = 0.298, p < 0.001), hand tremor (beta = 0.211, p = 0.001), positive family history (beta = 0.171, p = 0.012), and calf hypertrophy (beta = 0.120, p = 0.043). In the final DM2-EDS, based on the beta values, symptoms were associated with the following values: cataracts (present 3.4, absent 0), myotonia (present 2.5, absent 0), tremor (present 1.7, absent 0), family history (positive 1.4, negative 0), and calf hypertrophy (present 1.0, absent 0). A cut-off value on DM2-EDS of 3.25 of maximum 10 points had a sensitivity of 84% and specificity of 81% to diagnose DM2. CONCLUSION: Significant predictors of DM2 diagnosis in the neurology outpatient unit were identified. We made an easy-to-administer DM2-EDS score for early diagnosis of DM2.

Myotonic dystrophy type 1 in the COVID-19 era.

INTRODUCTION: Myotonic dystrophy type 1 (DM1) is the most prevalent muscular dystrophy in adults. People with DM1 might represent a high-risk population for respiratory infections, including COVID-19. Our aim was to evaluate the characteristics of COVID-19 infection and vaccination rate in DM1 patients. METHODS: This cross-sectional cohort study included 89 patients from the Serbian registry for myotonic dystrophies. Mean age at testing was 48.4 ± 10.4 years with 41 (46.1%) male patients. Mean duration of the disease was 24.0 ± 10.3 years. RESULTS: COVID-19 infection was reported by 36 (40.4%) DM1 patients. Around 14% of patients had a more severe form of COVID-19 requiring hospitalization. The severity of COVID-19 was in accordance with the duration of DM1. A severe form of COVID-19 was reported in 20.8% of patients who were not vaccinated against SARS-CoV-2 and in none of the vaccinated ones. The majority of 89 tested patients (66.3%) were vaccinated against SARS-CoV-2. About half of them (54.2%) received three doses and 35.6% two doses of vaccine. Mild adverse events after vaccination were recorded in 20.3% of patients. CONCLUSIONS: The percentage of DM1 patients who suffered from COVID-19 was like in general population, but with more severe forms in DM1, especially in patients with longer DM1 duration. The study indicated an overall favorable safety profile of COVID-19 vaccines among individuals with DM1 and its ability to protect them from severe COVID-19.

Co-occurrence of DMPK expansion and CLCN1 mutation in a patient with myotonia.

INTRODUCTION: Myotonic disorders are a group of diseases affecting the muscle, in different ways. Myotonic dystrophy type 1 (DM1) is related to (CTG)n expansion in the 3-untranslated region of the dystrophia myotonica protein kinase (DMPK) gene and is the most frequent and disabling form, causing muscular, visibility, respiratory, and cardiac impairment. Non-dystrophic myotonias (NDMs) affect the skeletal muscle alone. In particular, mutations in the chloride channel (CLCN1) gene cause myotonia congenita (MC), which can have autosomal dominant or recessive inheritance. CASE REPORT: We describe a patient with a family history of asymptomatic or paucisymptomatic myotonia, who presented handgrip myotonia which sharply reduced after mexiletine administration. Molecular analysis showed both a paternally inherited DMPK expansion and a maternally inherited CLCN1 mutation. CONCLUSIONS: Only one other similar case was reported so far; however, the segregation of the two mutations and the characteristics of the muscle were not studied. Since our patient lacked the classical phenotypical and muscle histopathological characteristics of DM1 and showed mild splicing alterations despite a pathogenic DMPK expansion and the nuclear accumulation of toxic RNA, we may speculate that the co-occurrence of a CLCN1 mutation could have attenuated the severity of DM1 phenotype.

Molecular and Clinical Implications of Variant Repeats in Myotonic Dystrophy Type 1.

Myotonic dystrophy type 1 (DM1) is one of the most variable monogenic diseases at phenotypic, genetic, and epigenetic level. The disease is multi-systemic with the age at onset ranging from birth to late age. The underlying mutation is an unstable expansion of CTG repeats in the DMPK gene, varying in size from 50 to >1000 repeats. Generally, large expansions are associated with an earlier age at onset. Additionally, the most severe, congenital DM1 form is typically associated with local DNA methylation. Genetic variability of DM1 mutation is further increased by its structural variations due to presence of other repeats (e.g., CCG, CTC, CAG). These variant repeats or repeat interruptions seem to confer an additional level of epigenetic variability since local DNA methylation is frequently associated with variant CCG repeats independently of the expansion size. The effect of repeat interruptions on DM1 molecular pathogenesis is not investigated enough. Studies on patients indicate their stabilizing effect on DMPK expansions because no congenital cases were described in patients with repeat interruptions, and the age at onset is frequently later than expected. Here, we review the clinical relevance of repeat interruptions in DM1 and genetic and epigenetic characteristics of interrupted DMPK expansions based on patient studies.

Guidelines on clinical presentation and management of nondystrophic myotonias.

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. In the absence of genetic confirmation, the diagnosis is supported by detailed electrophysiological testing, exclusion of other related disorders, and analysis of a variant of uncertain significance if present. Symptomatic treatment with a sodium channel blocker, such as mexiletine, is usually the first step in management, as well as educating patients about potential anesthetic complications.

Aberrant regulation of epigenetic modifiers contributes to the pathogenesis in patients with selenoprotein N-related myopathies.

Congenital myopathies are early onset, slowly progressive neuromuscular disorders of variable severity. They are genetically and phenotypically heterogeneous and caused by pathogenic variants in several genes. Multi-minicore Disease, one of the more common congenital myopathies, is frequently caused by recessive variants in either SELENON, encoding the endoplasmic reticulum glycoprotein selenoprotein N or RYR1, encoding a protein involved in calcium homeostasis and excitation-contraction coupling. The mechanism by which recessive SELENON variants cause Multiminicore disease (MmD) is unclear. Here, we extensively investigated muscle physiological, biochemical and epigenetic modifications, including DNA methylation, histone modification, and noncoding RNA expression, to understand the pathomechanism of MmD. We identified biochemical changes that are common in patients harboring recessive RYR1 and SELENON variants, including depletion of transcripts encoding proteins involved in skeletal muscle calcium homeostasis, increased levels of Class II histone deacetylases (HDACs) and DNA methyltransferases. CpG methylation analysis of genomic DNA of patients with RYR1 and SELENON variants identified >3,500 common aberrantly methylated genes, many of which are involved in calcium signaling. These results provide the proof of concept for the potential use of drugs targeting HDACs and DNA methyltransferases to treat patients with specific forms of congenital myopathies.

Dysregulation of Circular RNAs in Myotonic Dystrophy Type 1.

Circular RNAs (circRNAs) constitute a recently re-discovered class of non-coding RNAs functioning as sponges for miRNAs and proteins, affecting RNA splicing and regulating transcription. CircRNAs are generated by "back-splicing", which is the linking covalently of 3'- and 5'-ends of exons. Thus, circRNA levels might be deregulated in conditions associated with altered RNA-splicing. Significantly, growing evidence indicates their role in human diseases. Specifically, myotonic dystrophy type 1 (DM1) is a multisystemic disorder caused by expanded CTG repeats in the DMPK gene which results in abnormal mRNA-splicing. In this investigation, circRNAs expressed in DM1 skeletal muscles were identified by analyzing RNA-sequencing data-sets followed by qPCR validation. In muscle biopsies, out of nine tested, four transcripts showed an increased circular fraction: CDYL, HIPK3, RTN4_03, and ZNF609. Their circular fraction values correlated with skeletal muscle strength and with splicing biomarkers of disease severity, and displayed higher values in more severely affected patients. Moreover, Receiver-Operating-Characteristics curves of these four circRNAs discriminated DM1 patients from controls. The identified circRNAs were also detectable in peripheral-blood-mononuclear-cells (PBMCs) and the plasma of DM1 patients, but they were not regulated significantly. Finally, increased circular fractions of RTN4_03 and ZNF609 were also observed in differentiated myogenic cell lines derived from DM1 patients. In conclusion, this pilot study identified circRNA dysregulation in DM1 patients.

The analysis of myotonia congenita mutations discloses functional clusters of amino acids within the CBS2 domain and the C-terminal peptide of the ClC-1 channel.

Myotonia congenita (MC) is a skeletal-muscle hyperexcitability disorder caused by loss-of-function mutations in the ClC-1 chloride channel. Mutations are scattered over the entire sequence of the channel protein, with more than 30 mutations located in the poorly characterized cytosolic C-terminal domain. In this study, we characterized, through patch clamp, seven ClC-1 mutations identified in patients affected by MC of various severities and located in the C-terminal region. The p.Val829Met, p.Thr832Ile, p.Val851Met, p.Gly859Val, and p.Leu861Pro mutations reside in the CBS2 domain, while p.Pro883Thr and p.Val947Glu are in the C-terminal peptide. We showed that the functional properties of mutant channels correlated with the clinical phenotypes of affected individuals. In addition, we defined clusters of ClC-1 mutations within CBS2 and C-terminal peptide subdomains that share the same functional defect: mutations between 829 and 835 residues and in residue 883 induced an alteration of voltage dependence, mutations between 851 and 859 residues, and in residue 947 induced a reduction of chloride currents, whereas mutations on 861 residue showed no obvious change in ClC-1 function. This study improves our understanding of the mechanisms underlying MC, sheds light on the role of the C-terminal region in ClC-1 function, and provides information to develop new antimyotonic drugs.

Reduction of toxic RNAs in myotonic dystrophies type 1 and type 2 by the RNA helicase p68/DDX5.

Myotonic dystrophies type 1 (DM1) and type 2 (DM2) are neuromuscular diseases, caused by accumulation of CUG and CCUG RNAs in toxic aggregates. Here we report that the increased stability of the mutant RNAs in both types of DM is caused by deficiency of RNA helicase p68. We have identified p68 by studying CCUG-binding proteins associated with degradation of the mutant CCUG repeats. Protein levels of p68 are reduced in DM1 and DM2 biopsied skeletal muscle. Delivery of p68 in DM1/2 cells causes degradation of the mutant RNAs, whereas delivery of p68 in skeletal muscle of DM1 mouse model reduces skeletal muscle myopathy and atrophy. Our study shows that correction of p68 may reduce toxicity of the mutant RNAs in DM1 and in DM2.

Slowly progressing varicella zoster brainstem encephalitis complicating Ramsay Hunt syndrome in an immunocompetent patient: case report and review of the literature.

A 56-year-old immunocompetent male developed brainstem encephalitis complicating Ramsay Hunt syndrome. The disease had a slowly progressing course of months after the triggering infection, much longer than previously reported. Furthermore, magnetic resonance imaging, physical-chemical, and cell count analyses on cerebrospinal fluid were normal, whereas polymerase chain reaction for varicella zoster virus DNA was positive. The simultaneous negativity of both imaging and basic CSF exams is very rare, although possible event which confirms the irreplaceable role of viral screening on CSF. A systematic review of similar reports with highlights on the unusual aspects of our case is also presented.

Myotonic dystrophy type 2 and modifier genes: an update on clinical and pathomolecular aspects.

Myotonic dystrophy (DM) is the most common adult muscular dystrophy, characterized by autosomal dominant progressive myopathy, myotonia, and multiorgan involvement. To date, two distinct forms caused by similar mutations in two different genes have been identified: myotonic dystrophy type 1 (DM1) and myotonic dystrophy type 2 (DM2). Aberrant transcription and mRNA processing of multiple genes due to RNA-mediated toxic gain-of function has been suggested to cause the complex phenotype in DM1 and DM2. However, despite clinical and genetic similarities, DM1 and DM2 may be considered as distinct disorders. This review is an update on the latest findings specific to DM2, including explanations for the differences in clinical manifestations and pathophysiology between the two forms of myotonic dystrophies.

Clusters of cognitive impairment among different phenotypes of myotonic dystrophy type 1 and type 2.

Neuropsychological examinations in myotonic dystrophy (DM) patients show a great variability of results from a condition of intellectual disability to the subtle cognitive impairments. It is unclear if different clusters of neuropsychological deficits appear in different phenotypes of DM, or if there are patients with no cognitive deficit at all. The aim of this study is to assess cognitive impairments among patients with different phenotypes of DM type 1 (DM1) and type 2 (DM2), and to potentially define cognitive clusters in these disorders. Study comprised 101 DM1 and 46 DM2 adult patients who were genetically confirmed. Patients underwent analysis of five cognitive domains (visuospatial, executive, attention, memory and language). Virtually all DM1 patients had cognitive defect with approximately 2-3 cognitive domains affected. On the other hand, one-third of DM2 patients had completely normal neuropsychological findings, and in other two-thirds approximately 1-2 domains were affected. Cluster analysis showed that in both diseases visuospatial and executive dysfunctions seemed to be the main cognitive defects, while memory and language impairments appeared in more severe phenotypes. Our results showed that a single form of DM1 or DM2 may consist of several cognitive clusters. Understanding of cognitive impairments in DM is very important to follow positive and side effects in ongoing and future clinical trials.

Electromechanical delays during a fatiguing exercise and recovery in patients with myotonic dystrophy type 1.

PURPOSE: The partitioning of the electromechanical delay by an electromyographic (EMG), mechanomyographic (MMG) and force combined approach can provide further insight into the electrochemical and mechanical processes involved with skeletal muscle contraction and relaxation. The aim of the study was to monitor by this combined approach the changes in delays' electrochemical and mechanical components throughout a fatiguing task and during recovery in patients with myotonic dystrophy type 1 (DM1), who present at the skeletal muscle level fibres rearrangement, muscle weakness and myotonia, especially in the distal muscles. METHODS: After assessing maximum voluntary contraction (MVC), 14 male patients with DM1 and 14 healthy controls (HC) performed a fatiguing exercise at 50% MVC until exhaustion. EMG, MMG, and force signals were recorded from tibialis anterior and vastus lateralis muscles. The electromechanical delay during contraction (DelayTOT) and relaxation (R-DelayTOT) components, EMG and MMG root mean square (RMS) and mean frequency (MF) were calculated off-line. RESULTS: The fatiguing exercise duration was similar in both groups. In patients with DM1, delays components were significantly longer compared to HC, especially in the distal muscle during relaxation. Delays components recovered quickly from the fatiguing exercise in HC than in patients with DM1 in both muscles. CONCLUSIONS: The alterations in delays observed in DM1 during the fatiguing exercise may indicate that also the lengthening of the electrochemical and mechanical processes during contraction and relaxation could play a role in explaining exercise intolerance in this pathology.

Myotonic dystrophies: An update on clinical aspects, genetic, pathology, and molecular pathomechanisms.

Myotonic dystrophy (DM) is the most common adult muscular dystrophy, characterized by autosomal dominant progressive myopathy, myotonia and multiorgan involvement. To date two distinct forms caused by similar mutations have been identified. Myotonic dystrophy type 1 (DM1, Steinert's disease) is caused by a (CTG)n expansion in DMPK, while myotonic dystrophy type 2 (DM2) is caused by a (CCTG)n expansion in ZNF9/CNBP. When transcribed into CUG/CCUG-containing RNA, mutant transcripts aggregate as nuclear foci that sequester RNA-binding proteins, resulting in spliceopathy of downstream effector genes. However, it is now clear that additional pathogenic mechanism like changes in gene expression, protein translation and micro-RNA metabolism may also contribute to disease pathology. Despite clinical and genetic similarities, DM1 and DM2 are distinct disorders requiring different diagnostic and management strategies. This review is an update on the recent advances in the understanding of the molecular mechanisms behind myotonic dystrophies. This article is part of a Special Issue entitled: Neuromuscular Diseases: Pathology and Molecular Pathogenesis.

Brain Connectomics' Modification to Clarify Motor and Nonmotor Features of Myotonic Dystrophy Type 1.

The adult form of myotonic dystrophy type 1 (DM1) presents with paradoxical inconsistencies between severity of brain damage, relative preservation of cognition, and failure in everyday life. This study, based on the assessment of brain connectivity and mechanisms of plasticity, aimed at reconciling these conflicting issues. Resting-state functional MRI and graph theoretical methods of analysis were used to assess brain topological features in a large cohort of patients with DM1. Patients, compared to controls, revealed reduced connectivity in a large frontoparietal network that correlated with their isolated impairment in visuospatial reasoning. Despite a global preservation of the topological properties, peculiar patterns of frontal disconnection and increased parietal-cerebellar connectivity were also identified in patients' brains. The balance between loss of connectivity and compensatory mechanisms in different brain networks might explain the paradoxical mismatch between structural brain damage and minimal cognitive deficits observed in these patients. This study provides a comprehensive assessment of brain abnormalities that fit well with both motor and nonmotor clinical features experienced by patients in their everyday life. The current findings suggest that measures of functional connectivity may offer the possibility of characterizing individual patients with the potential to become a clinical tool.

Gonadal failure is associated with visceral adiposity in myotonic dystrophies.

BACKGROUND: Hypogonadism occurs in myotonic dystrophies type 1 (MD1) and type 2 (MD2). Sertoli and Leydig cell secretions, including insulin-like peptide-3 (INSL3), anti-Müllerian hormone (AMH) and inhibin B, were evaluated in male patients with MD. DESIGN: Academic settings. Forty-four male patients with MD [31 MD1, 13 MD2, aged 59 (50-64) years, median (interquartile range)], age-, sex- and BMI-matched non-MD hypogonadal patients (n = 14) and healthy controls (n = 32). Serum FSH, LH, inhibin B, AMH, testosterone (T) and INSL3 were measured; fat and muscle masses were evaluated by DEXA. RESULTS: Overt primary hypogonadism occurred in 29% of patients with MD1 and 46% of patients with MD2. Considering subclinical forms, the prevalence increased to 69% of MD1 and 100% of MD2. A half of patients with MD experienced symptoms. INSL3 levels were unaffected in most patients with MD. By contrast, AMH and inhibin B were reduced in most patients with MD and unrelated to age. Patients with MD showed increased body and visceral fat. Free T levels were negatively predicted by fat mass, and AMH and FSH levels were negatively correlated with waist/hip ratio and fat mass. AMH, inhibin B and FSH levels positively correlated with muscle strength and muscle mass. CONCLUSIONS: AMH and inhibin B secretion failures are common in male patients with MD and are more severe than Leydig cell hormones impairment. AMH and inhibin B measurements might provide clinical utility in evaluating fertility in patients with MD. Serum T, AMH and inhibin B productions are negatively influenced by increased fat mass, while AMH and inhibin B might be markers of muscle impairment.

Transcranial brain parenchyma sonographic findings in patients with myotonic dystrophy type 1 and 2.

Introduction: Myotonic dystrophy type 1 (DM1) and 2 (DM2) are genetically determined progressive muscular disorders with multisystemic affection, including brain involvement. Transcranial sonography (TCS) is a reliable diagnostic tool for the investigation of deep brain structures. We sought to evaluate TCS findings in genetically confirmed DM1 and DM2 patients, and further correlate these results with patients' clinical features. Methods: This cross-sectional study included 163 patients (102 DM1, 61 DM2). Echogenicity of the brainstem raphe (BR) and substantia nigra (SN) as well as the diameter of the third ventricle (DTV) were assessed by TCS. Patients were evaluated using the Hamilton Depression Rating Scale, Fatigue Severity Scale and Daytime Sleepiness Scale. Results: SN hyperechogenicity was observed in 40% of DM1 and 34% of DM2 patients. SN hypoechogenicity was detected in 17% of DM1 and 7% of DM2 patients. BR hypoechogenicity was found in 36% of DM1 and 47% of DM2 subjects. Enlarged DTV was noted in 19% of DM1 and 15% of DM2 patients. Older, weaker, depressive, and fatigued DM1 patients were more likely to have BR hypoechogenicity (p < 0.05). DTV correlated with age and disease duration in DM1 (p < 0.01). In DM2 patients SN hyperechogenicity correlated with fatigue. Excessive daytime sleepiness was associated with hypoechogenic BR (p < 0.05) and enlarged DVT (p < 0.01) in DM2 patients. Conclusions: TCS is an easy applicable and sensitive neuroimaging technique that could offer new information regarding several brainstem structures in DM1 and DM2. This may lead to better understanding of the pathogenesis of the brain involvement in DM with possible clinical implications.

Case report: Dihydropyridine receptor (CACNA1S) congenital myopathy, a novel phenotype with early onset periodic paralysis.

Introduction: CACNA1S related congenital myopathy is an emerging recently described entity. In this report we describe 2 sisters with mutations in the CACNA1S gene and the novel phenotype of congenital myopathy and infantile onset episodic weakness. Clinical description: Both sisters had neonatal onset hypotonia, muscle weakness, and delayed walking. Episodic weakness started in infancy and continued thereafter, provoked mostly by cold exposure. Muscle imaging revealed fat replacement of gluteus maximus muscles. Next generation sequencing found the missense p.Cys944Tyr variant and the novel splicing variant c.3526-2A>G in CACNA1S. Minigene assay revealed the splicing variant caused skipping of exon 28 from the transcript, potentially affecting protein folding and/or voltage dependent activation. Conclusion: This novel phenotype supports the notion that there are age related differences in the clinical expression of CACNA1S gene mutations. This expands our understanding of mutations located in regions of the CACNA1S outside the highly conserved S4 segment, where most mutations thus far have been identified.

Main features and disease outcome of congenital myotonic dystrophy - experience from a single tertiary center.

Congenital myotonic dystrophy type 1 (CDM1) is a rare neuromuscular disease. The aim of our study was to evaluate clinical variability of CDM1 and factors that may influence survival in CDM1. Research included 24 pediatric patients with CDM1. Most of our patients had some form of hypoxic ischemic encephalopathy (HIE) (74 %), from mild to severe. Prolonged and complicated deliveries (75 %), high percentage of children resuscitated at birth (57 %) and respiratory insufficiency (46 %) with consequent hypoxia were the main reasons that could explain high percentage of HIE. Therapeutic hypothermia was applied in three children with poor outcome. Median survival of all CDM1 was 14.2 ± 1.5 years. Six patients had a fatal outcome (25 %). Their mean age of death was 3.0 ± 2.8 years. Poor prognostic factors for the survival of our CDM1 patients were: preterm delivery, resuscitation at birth, severe HIE, hypothermia treatment and permanent mechanical ventilation. Respiratory insufficiency was the main life-threatening factor. Our data clearly indicates the need to develop natural history studies in CDM1 in order to enhance the standards of care and to develop clinical trials investigating causative therapies in pediatric patients with CDM1.

Clinical aspects, molecular pathomechanisms and management of myotonic dystrophies.

Myotonic dystrophy (DM) is the most common adult muscular dystrophy, characterized by autosomal dominant progressive myopathy, myotonia and multiorgan involvement. To date two distinct forms caused by similar mutations have been identified. Myotonic dystrophy type 1 (DM1, Steinert's disease) was described more than 100 years ago and is caused by a (CTG)n expansion in DMPK, while myotonic dystrophy type 2 (DM2) was identified only 18 years ago and is caused by a (CCTG)n expansion in ZNF9/CNBP. When transcribed into CUG/CCUG-containing RNA, mutant transcripts aggregate as nuclear foci that sequester RNA-binding proteins, resulting in spliceopathy of downstream effector genes. Despite clinical and genetic similarities, DM1 and DM2 are distinct disorders requiring different diagnostic and management strategies. DM1 may present in four different forms: congenital, early childhood, adult onset and late-onset oligosymptomatic DM1. Congenital DM1 is the most severe form of DM characterized by extreme muscle weakness and mental retardation. In DM2 the clinical phenotype is extremely variable and there are no distinct clinical subgroups. Congenital and childhood-onset forms are not present in DM2 and, in contrast to DM1, myotonia may be absent even on EMG. Due to the lack of awareness of the disease among clinicians, DM2 remains largely underdiagnosed. The delay in receiving the correct diagnosis after onset of first symptoms is very long in DM: on average more than 5 years for DM1 and more than 14 years for DM2 patients. The long delay in the diagnosis of DM causes unnecessary problems for the patients to manage their lives and anguish with uncertainty of prognosis and treatment.