Myotonic dystrophies type 1 and 2: anesthetic care.

SUMMARY: Myotonic dystrophy is classified as one of the myotonic syndromes although myotonia is only a minor characteristic of it. It is, in fact, also a multisystem disease with cardiac, digestive, ocular, and endocrine abnormalities. Two subgroups are currently identified with many similarities: DM1 refers to classic dystrophia myotonica (Steinert disease), while DM2, formerly called proximal myotonic myopathy has a later onset. The congenital form is present only in DM1. The genetic causes of DM1 and 2 are different but end up in a similar way of altering RNAm processing and splicing of other genes. The anesthetic risk is increased in case of DM1 type. This review summarizes current knowledge concerning the pathophysiology and anesthetic management of this disease in children and adults.

Pain in patients with myotonic dystrophy type 2: a postal survey in Finland.

INTRODUCTION: Widespread musculoskeletal pain is a well-known symptom of myotonic dystrophy type 2 (DM2), but so far it has been addressed in only a few studies. METHODS: A postal survey for all traceable DM2 patients (n = 132) was conducted. A specific questionnaire, and severity and interference subscales of the Brief Pain Inventory, quality of life (RAND-36), and modified Beck Depression Inventory were completed. RESULTS: The response rate was 70%. The mean age of respondents was 53 years, 59% of whom were women. Current pain was reported by 54%. Lifetime prevalence of pain was 76%. The mean intensity of pain at its highest in the last week was 5.9, and 2.3 at its lowest (on a numerical rating scale of 0-10). Quality of life was lower in DM2 patients who reported pain. In 18%, the depression score was noticeably different. CONCLUSIONS: Pain of moderate severity and unpleasant muscular symptoms are common in DM2. DM2 should be taken into consideration in the differential diagnosis of musculoskeletal pain.

Predictors of atrio-ventricular conduction disease, long-term outcomes in patients with myotonic dystrophy types I and II.

BACKGROUND: Patients with myotonic dystrophy (DM) have an annual mortality of approximately 3.5%, one-third of which is sudden cardiac death. The predictors of cardiac conduction disease in these patients are incompletely defined. METHODS: A single-center cohort study included 211 patients with DM type 1 (DM1) and 25 DM type 2 (DM2). A severe electrocardiogram (ECG) abnormality was defined as a PR interval of ≥240 ms or QRS duration of ≥120 ms. RESULTS: A severe ECG abnormality was found in 24% of DM1 patients and 17% of DM2 patients. Among DM1 patients, those with a severe ECG abnormality were older (41.6 ± 14.6 vs 35.4 ± 12.6 years) and more likely to have hypertension (13.2% vs 4.2%, P = 0.038), heart failure (4.4% vs 0%, P = 0.056), atrial arrhythmias (6.6% vs 0.7%, P < 0.001), a higher number of trinucleotide repeats (689 ± 451 vs 474 ± 322, P = 0.01), and a family history of sudden cardiac death (26.7% vs 5.6%, P < 0.001) or pacemaker implantation (20% vs 0.7%, P < 0.001). Pacemakers or defibrillators were implanted in 14% of all patients, including 65% of patients with severe ECG abnormalities. During 57 ± 46 months, 13 patients died (1.16% per year), including three patients who died suddenly, two of whom had normally functioning pacemakers. CONCLUSION: In DM1, atrio-ventricular conduction disease is associated with increasing age, concomitant cardiovascular disease, nucleotide repeat length, and family history. The systematic identification of conduction disease and aggressive use of prophylactic pacemakers is associated with low rate of sudden cardiac death.

Paramyotonia congenita in a Slovak population: Genetic and pedigree analysis of 3 families.

BACKGROUND: Paramyotonia congenita is a non-dystrophic myotonia, in which muscle relaxation is delayed after voluntary or evoked contraction. This condition cannot be distinguished on the basis of symptoms and signs alone. It requires consideration of genetics as more than 100 mutations in the CLCN1 gene and at least 20 mutations in the SCN4A gene are associated with the clinical features of the non-dystrophic myotonias. Only a few families with the described features but no genetic testing have been reported in Slovakia. This prompted us to investigate genetic mutations in the SCN4A gene in 3 Slovak families clinically diagnosed with paramyotonia. SUBJECTS AND METHODS: Genomic DNA of the family members was extracted from peripheral blood and amplified by polymerase chain reaction. SCN4A variants were screened by Sanger sequencing. RESULTS: Our results revealed 2 potential disease-causing mutations present in the probands and affected family members - mutations c.3938C > T (p.T1313M) in two families and mutation c.2111C>T (p. T704M) in one family. CONCLUSION: Our results may help to identify genetic determinants as well as clarify genotype-phenotype relationships in patients with paramyotonia in Slovakia.

Autism spectrum conditions in myotonic dystrophy type 1: a study on 57 individuals with congenital and childhood forms.

Myotonic dystrophy type 1 (DM1) is an autosomal dominant disorder, caused by an expansion of a CTG triplet repeat in the DMPK gene. The aims of the present study were to classify a cohort of children with DM1, to describe their neuropsychiatric problems and cognitive level, to estimate the size of the CTG expansion, and to correlate the molecular findings with the neuropsychiatric problems. Fifty-seven children and adolescents (26 females; 31 males) with DM1 (CTG repeats > 40) were included in the study. The following instruments were used: Autism Diagnostic Interview-Revised (ADI-R), 5-15, Griffiths Mental Development Scales, and the Wechsler Scales. Based on age at onset and presenting symptoms, the children were divided into four DM1 groups; severe congenital (n = 19), mild congenital (n = 18), childhood (n = 18), and classical DM1 (n = 2). Forty-nine percent had an autism spectrum disorder (ASD) and autistic disorder was the most common diagnosis present in 35% of the subjects. Eighty-six percent of the individuals with DM1 had mental retardation (MR), most of them moderate or severe MR. ASD was significantly correlated with the DM1 form; the more severe the form of DM1, the higher the frequency of ASD. The frequency of ASD increased with increasing CTG repeat expansions. ASD and/or other neuropsychiatric disorders such as attention deficit hyperactivity disorder, and Tourette's disorder were found in 54% of the total DM1 group. In conclusion, awareness of ASD comorbidity in DM1 is essential. Further studies are warranted to elucidate the molecular etiology causing neurodevelopmental symptoms such as ASD and MR in DM1.

Prevalence and mutation spectrum of skeletal muscle channelopathies in the Netherlands.

Few reliable data exist on the prevalence of skeletal muscle channelopathies. We determined the minimum point prevalence of genetically-defined skeletal muscle channelopathies in the Netherlands and report their mutation spectrum. Minimum point prevalence rates were calculated as number of genetically-confirmed skeletal muscle channelopathy patients (CLCN1, SCN4A, CACNA1S and KCNJ2 gene mutations) in the Netherlands (1990-2015) divided by the total number of at-risk individuals. Rates were expressed as cases/100.000 and 95% confidence intervals were calculated based on Poisson distribution. Results of standardized genetic diagnostic procedures were used to analyze mutation spectra. We identified 405 patients from 234 unrelated pedigrees, resulting in a minimum point prevalence of 2.38/100.000 (95% CI 2.16-2.63) for skeletal muscle channelopathies in the Netherlands. Minimum point prevalence rates for the disease groups, non-dystrophic myotonia and periodic paralysis, were 1.70/100.000 and 0.69/100.000 respectively. Sixty-one different CLCN1 mutations (including 12 novel mutations) were detected in myotonia congenita. Twenty-eight different SCN4A missense mutations (including three novel mutations) were identified in paramyotonia congenita/sodium channel myotonia, hypokalemic periodic paralysis and hyperkalemic periodic paralysis. Four different CACNA1S missense mutations were detected in hypokalemic periodic paralysis and five KCNJ2 missense mutations in Andersen-Tawil syndrome. The minimum point prevalence rates for genetically-defined skeletal muscle channelopathies confirm their rare disease status in the Netherlands. Rates are almost twice as high as in the UK and more in line with pre-genetic prevalence estimates in parts of Scandinavia. Future diagnostic and therapeutic studies may benefit from knowledge of the mutation spectrum of skeletal muscle channelopathies.

Proximal myotonic myopathy: evidence for anticipation in families with linkage to chromosome 3q.

OBJECTIVE: To investigate anticipation in proximal myotonic myopathy (PROMM). BACKGROUND: PROMM is a recently described autosomal dominantly inherited disorder similar to but distinct from myotonic dystrophy (DM). DM belongs to the group of inherited disorders with anticipation caused by an unstable trinucleotide repeat expansion. In PROMM, no mutation has been identified, although PROMM has recently been mapped to a gene locus on chromosome 3q. METHODS: We investigated 10 German families with the PROMM phenotype and linkage to chromosome 3q. We based our analysis of anticipation on the age of disease onset. Anticipation was assumed if the offspring had first symptoms earlier in life than his or her affected parent. For statistical analysis Independence Estimating Equations (IEE) and a Monte-Carlo bootstrap were used. RESULTS: In 27 affected living parent-offspring pairs from these 10 families, the mean difference of disease onset was 18.8 years with either statistical analysis (p < 10-14 and p < 10-15). The mean disease onset interval in years was greater in father-offspring as compared to the mother-offspring pairs (p < 0.05; IEE). CONCLUSION: Our findings suggest the occurrence of anticipation in parent-offspring pairs from families with the PROMM phenotype and linkage to chromosome 3q. The different disease onset intervals in mother-offspring and father-offspring pairs could indicate a mild parent-of-origin effect. These observations are compatible with the suggestion that PROMM, like DM, may be a trinucleotide repeat associated disorder. In contrast to DM, anticipation in PROMM is milder, a congenital form does not seem to occur, and fertility does not appear to be affected.

[Molecular and genetic aspects of the myotonic conditions]. / Aspectos geneticos y moleculares de las enfermedades miotonicas.

AIM: The aim is to review the molecular and genetic aspects of the dystrophic and no dystrophic myotonias. BACKGROUND: Myotonic diseases are hereditary conditions of the skeletal muscle, classified in two groups depending on the symptoms. In the first group are the myotonic dystrophies, with the myotonic dystrophies type 1 and 2. In the second group are the channelopathies, characterized for the affected function of the ion channels. Myotonic dystrophy type 1, a neurodegenerative, progressive and disabling disease is caused by an expansion of the CTG trinucleotide, its size shows a positive correlation with the severity and negative with age of onset. There are enough insights to think that the gain of function of the mutant ARN is the pathophysiological mechanism occurring on this disease. Myotonic dystrophy type 2, less severe than type 1, is caused by an expansion of the CCTG tetranucleotide, its pathophysiological mechanism is similar to that one proposed for the type 1. In the second group we can find the chloride channelopathies, with autosomal dominant or recessive inheritance, caused by one of the 60 different mutations on the chloride channel gene; and the sodium channelopathies, group of three clinically overlapping diseases, with dominant heredity caused by one of the 25 different mutations on the sodium channel gene. CONCLUSIONS: These diseases are highly clinically variable, and even though their genetic base is known, it is necessary too much research in order to understand their pathophisiology and the phenotype genotype relationships.

The frequency and severity of cardiac involvement in myotonic dystrophy type 2 (DM2): long-term outcomes.

BACKGROUND: Frequency and severity of cardiac involvement in DM2 are still controversial. The aims of our study were to determine the frequency and progression of cardiac and muscle involvement in a relatively large cohort of patients with DM2 throughout Italy and Germany and to provide long-term outcomes in this disorder. METHODS: 104 DM2 and 117 DM1 patients underwent baseline and follow-up assessments of, ECG, 24h Holter monitoring, 2D echocardiography and electrophysiological study (EPS) when appropriate, and manual muscle strength testing (mean follow-up: 7.4 ± 4.1 for DM2 and 5.7 ± 4 years for DM1). RESULTS: Overall, 10% of DM2 patients vs 31% of DM1 patients had PR ≥ 200 ms and 17% of DM2 patients vs 48% of DM1 patients had QRSD ≥ 100 ms. Six patients with DM2 vs 28 patients with DM1 required PM/ICD implantations. DM2 patients were stronger than DM1 patients at baseline, but muscle strength worsened significantly over time (p<0.0001), just as in DM1, although at a slower annual rate. CONCLUSION: Our data demonstrate that the frequency and severity of cardiac involvement and of muscle weakness are reduced in DM2 compared to DM1 and that progression is slower and less severe. Nonetheless, careful cardiac evaluation is recommended in this patient population to identify patients at risk for potential major cardiac arrhythmias.

Prevalence study of genetically defined skeletal muscle channelopathies in England.

OBJECTIVES: To obtain minimum point prevalence rates for the skeletal muscle channelopathies and to evaluate the frequency distribution of mutations associated with these disorders. METHODS: Analysis of demographic, clinical, electrophysiologic, and genetic data of all patients assessed at our national specialist channelopathy service. Only patients living in the United Kingdom with a genetically defined diagnosis of nondystrophic myotonia or periodic paralysis were eligible for the study. Prevalence rates were estimated for England, December 2011. RESULTS: A total of 665 patients fulfilled the inclusion criteria, of which 593 were living in England, giving a minimum point prevalence of 1.12/100,000 (95% confidence interval [CI] 1.03-1.21). Disease-specific prevalence figures were as follows: myotonia congenita 0.52/100,000 (95% CI 0.46-0.59), paramyotonia congenita 0.17/100,000 (95% CI 0.13-0.20), sodium channel myotonias 0.06/100,000 (95% CI 0.04-0.08), hyperkalemic periodic paralysis 0.17/100,000 (95% CI 0.13-0.20), hypokalemic periodic paralysis 0.13/100,000 (95% CI 0.10-0.17), and Andersen-Tawil syndrome (ATS) 0.08/100,000 (95% CI 0.05-0.10). In the whole sample (665 patients), 15 out of 104 different CLCN1 mutations accounted for 60% of all patients with myotonia congenita, 11 out of 22 SCN4A mutations for 86% of paramyotonia congenita/sodium channel myotonia pedigrees, and 3 out of 17 KCNJ2 mutations for 42% of ATS pedigrees. CONCLUSION: We describe for the first time the overall prevalence of genetically defined skeletal muscle channelopathies in England. Despite the large variety of mutations observed in patients with nondystrophic myotonia and ATS, a limited number accounted for a large proportion of cases.

[Myotonic dystrophy type 2].

Myotonic dystrophies (DMs) are autosomal dominant disorders with multisystemic clinical features. DMs are categorized as DM1, caused by a (CTG)n expansion mutation in 19q13, and DM2, caused by a (CCTG)n expansion mutation in 3q21. The clinical features of DM2 are diffuse and proximal dominant weakness, wasting, myotonia, cardiac problems, cataracts, and insulinresistance. DM2 is milder than DM1. We compared the clinical features of both DMs and studied a Japanese patient with DM2 who had expansion mutations different from those usually attributed to the disease and originally discovered by European researchers. The detailed clinical features of the Japanese DM2 patient are described.

Population frequency of myotonic dystrophy: higher than expected frequency of myotonic dystrophy type 2 (DM2) mutation in Finland.

Myotonic dystrophy (DM) is the most common adult-onset muscular dystrophy with an estimated prevalence of 1/8000. There are two genetically distinct types, DM1 and DM2. DM2 is generally milder with more phenotypic variability than the classic DM1. Our previous data on co-segregation of heterozygous recessive CLCN1 mutations in DM2 patients indicated a higher than expected DM2 prevalence. The aim of this study was to determine the DM2 and DM1 frequency in the general population, and to explore whether the DM2 mutation functions as a modifier in other neuromuscular diseases (NMD) to account for unexplained phenotypic variability. We genotyped 5535 Finnish individuals: 4532 normal blood donors, 606 patients with various non-myotonic NMD, 221 tibial muscular dystrophy patients and their 176 healthy relatives for the DM2 and DM1 mutations. We also genotyped an Italian idiopathic non-myotonic proximal myopathy cohort (n = 93) for the DM2 mutation. In 5496 samples analyzed for DM2, we found three DM2 mutations and two premutations. In 5511 samples analyzed for DM1, we found two DM1 mutations and two premutations. In the Italian cohort, we identified one patient with a DM2 mutation. We conclude that the DM2 mutation frequency is significantly higher in the general population (1/1830; P-value = 0.0326) than previously estimated. The identification of DM2 mutations in NMD patients with clinical phenotypes not previously associated with DM2 is of particular interest and is in accord with the high overall prevalence. On the basis of our results, DM2 appears more frequent than DM1, with most DM2 patients currently undiagnosed with symptoms frequently occurring in the elderly population.

Left ventricular dysfunction and cardiac arrhythmias are frequent in type 2 myotonic dystrophy: a case control study.

In contrast with Steinert's disease (DM1), type 2 muscular dystrophy (DM2) is not known to be associated with a high prevalence of cardiac involvement. Our objective was to compare the results of detailed cardiac investigations in populations of DM2 and DM1 patients, and in controls. Thirty-eight DM2 patients (17 males; age=57.1+/-15.2years) were investigated for possible heart involvement, and their results compared with 76 age-sex matched DM1 patients and 76 controls. Cardiac abnormalities were present in 15 DM2 patients, including conductive defects in 14, systolic dysfunction in 6, supraventricular arrhythmias in 6 and stroke in 5 patients and were significantly more frequent than in controls. When compared to DM1 patients, conductive defects were less frequent, supraventricular arrhythmias had similar prevalence and there was a trend towards more frequent left ventricular dysfunction in DM2 patients. Our study suggests that systematic cardiac investigations should be recommended in these patients.

What causes paramyotonia in the United Kingdom? Common and new SCN4A mutations revealed.

OBJECTIVE: To study the clinical and genetic features in a large cohort of UK patients with sodium channel paramyotonia congenita. METHODS: We conducted a UK-wide clinical and molecular genetic study of patients presenting with a phenotype suggestive of paramyotonia congenita. RESULTS: We identified 42 affected individuals (28 kindreds). All cases met our core criteria for a clinical diagnosis of paramyotonia congenita. Seventy-five percent of patients (32 patients/20 kindreds) had SCN4A mutations. Twenty-nine subjects from 18 kindreds had exon 22 and 24 mutations, confirming these exons to be hot spots. Unexpectedly, 3 of these subjects harbored mutations previously described with potassium-aggravated myotonia (G1306A, G1306E). We identified two new mutations (R1448L and L1436P). Ten cases (8 kindreds) without mutations exhibited paramyotonia congenita with prominent pain and weakness. CONCLUSIONS: This study identifies two new mutations, confirms SCN4A as a common cause of paramyotonia congenita in the UK, and suggests further allelic and possibly genetic heterogeneity.