Emery-Dreifuss muscular dystrophy

Echocardiographic Features of Cardiomyopathy in Emery-Dreifuss Muscular Dystrophy

Background

Emery-Dreifuss muscular dystrophy (EDMD) is a very rare type of muscular dystrophy characterized by musculoskeletal abnormalities accompanied by cardiac defects. Two most common genetic subtypes are EDMD1 due to EMD and EDMD2 caused by LMNA gene mutations. The aim of the study was to characterize and compare the cardiac morphology and function in the two main genetic subgroups of EDMD with the use of echocardiography.

Methods

41 patients with EDMD (29 EDMD1 and 12 EDMD2) as well as 25 healthy controls were enrolled in our study. Transthoracic echo with the use of a prescribed protocol was performed.

Results

Highly statistically significant differences with regard to left ventricle (LV) volumes between the EDMD and the control group were found. 51% of EDMD patients had an enlarged left atrium and as many as 71% had an enlarged right atrium. The LV ejection fraction (LVEF) was significantly lower in EDMD patients than in the control group which corresponded also with a lower systolic velocity of the mitral annulus. 43% of EDMD patients had LVEF below the normal limit. Diastolic dysfunction was detected in 17% of EDMD patients. There were no significant differences between the two types of EDMD in terms of diameters and volumes of any chamber, as well as the systolic function of both left and right ventricles.

Conclusions

A significant number of EDMD patients present LV dilatation and different degrees of systolic dysfunction. Dilatation of the atria dominates over ventricle dilatation. We did not present any significant differences between EDMD1 and EDMD2 in terms of the morphology and the function of the heart.

Emery-Dreifuss muscular dystrophy: focal point nuclear envelope

PURPOSE OF REVIEW

Emery-Dreifuss muscular dystrophy (EDMD) is caused by mutations in EMD encoding emerin and LMNA encoding A-type lamins, proteins of the nuclear envelope. In the past decade, there has been an extraordinary burst of research on the nuclear envelope. Discoveries resulting from this basic research have implications for better understanding the pathogenesis and developing treatments for EDMD.

RECENT FINDINGS

Recent clinical research has confirmed that EDMD is one of several overlapping skeletal muscle phenotypes that can result from mutations in EMD and LMNA with dilated cardiomyopathy as a common feature. Basic research on the nuclear envelope has provided new insights into how A-type lamins and emerin function in force transmission throughout the cell, which may be particularly important in striated muscle. Much of the recent research has focused on the heart and LMNA mutations. Prevalence and outcome studies have confirmed the relative severity of cardiac disease. Robust mouse models of EDMD caused by LMNA mutations has allowed for further insight into pathogenic mechanisms and potentially beneficial therapeutic approaches.

SUMMARY

Recent clinical and basic research on EDMD is gradually being translated to clinical practice and possibly novel therapies.

Restoration of Global Sagittal Alignment After Surgical Correction of Cervical Hyperlordosis in a Patient with Emery-Dreifuss Muscular Dystrophy: A Case Report

CASE

We report a rare cervical hyperlordotic deformity in a 19-year-old woman with Emery-Dreifuss muscular dystrophy and concomitant scoliosis. After standard posterolateral instrumentation and fusion of C2-T1 and extensive soft-tissue release, her neck pain improved and unassisted maintenance of cervical alignment and horizontal gaze were preserved through an 8-year follow-up. More importantly, she exhibited reciprocal correction of compensatory global sagittal malalignment, including lumbar lordosis.

CONCLUSIONS

This case highlights the importance of full-spine analysis for all patients with spinal deformity to identify and differentiate primary driver(s) of deformity from compensatory mechanisms to individualize treatment toward what truly drives the patient's disability.

Emery-Dreifuss muscular dystrophy

Emery-Dreifuss muscular dystrophy (EDMD) is a rare muscular dystrophy, but is particularly important to diagnose due to frequent life-threatening cardiac complications. EDMD classically presents with muscle weakness, early contractures, cardiac conduction abnormalities and cardiomyopathy, although the presence and severity of these manifestations vary by subtype and individual. Associated genes include EMD, LMNA, SYNE1, SYNE2, FHL1, TMEM43, SUN1, SUN2, and TTN, encoding emerin, lamin A/C, nesprin-1, nesprin-2, FHL1, LUMA, SUN1, SUN2, and titin, respectively. The Online Mendelian Inheritance in Man database recognizes subtypes 1 through 7, which captures most but not all of the associated genes. Genetic diagnosis is essential whenever available, but traditional diagnostic tools can help steer the evaluation toward EDMD and assist with interpretation of equivocal genetic test results. Management is primarily supportive, but it is important to monitor patients closely, especially for potential cardiac complications. There is a high potential for progress in the treatment of EDMD in the coming years.

A novel EMD mutation in a Chinese family with initial diagnosis of conduction cardiomyopathy

INTRODUCTION

Emery-Dreifuss muscular dystrophy (EDMD) is a hereditary myopathy characterized as triad of muscular dystrophy, joint contractures, and conduction cardiomyopathy. In this study, we diagnosed a X-linked recessive EDMD patient with severe conduction cardiomyopathy while noteless muscular and joint disorders.

METHODS

A Chinese cardiomyopathy family spanning four generations was enrolled in the study. Targeted next-generation sequencing (NGS) was performed to identify the underlying mutation in the proband and validated by Sanger sequencing. Segregation analysis was applied to all 13 participants.

RESULTS

A novel frameshift mutation (c.253_254insT, p.Y85Lfs*8) of emerin gene (EMD) was found and co-segregated with family members. Other than the typical manifestations of X-linked EDMD, this patient presented inconspicuous muscular disorders which were later diagnosed after the mutation been identified.

CONCLUSIONS

This study enriches the EMD gene mutation database and reminds us of the possibility of EDMD while encountering patients with severe heart rhythm defects or dilated cardiomyopathy of unknown etiology, even if they have neither obvious skeletal muscle disorder nor joint involvement.

Occurrence of Emery-Dreifuss muscular dystrophy in a rural setting of Cameroon: a case report and review of the literature

Background

Emery-Dreifuss muscular dystrophy is a rare genetic muscular disease, presenting mainly with contractures, weakness and cardiac conduction abnormalities. Its clinical and laboratory similarities to other muscular dystrophies, and rarity poses diagnostic challenges, requiring a high index of suspicion in resource limited settings.

Case presentation

An 8 year old sub-Saharan male presented with rigidity and deformity of both elbows and ankles, and weakness of the upper limbs and lower limbs for duration of 4 months. This progressed to inability to stand and walk. There was no mental impairment. Physical examination was remarkable for contractures of the elbows and ankles, and wasting of muscles of the limbs and trunk, with a scapulohumeroperoneal pattern, and tachycardia. After laboratory investigations, a diagnosis of Emery-Dreifuss muscular dystrophy was suspected. Physiotherapy was started, wheel chair was prescribed, and referral to a specialist center was done for appropriate management.

Conclusions

Emery-Dreifuss muscular dystrophy is a rare disabling muscular disease which poses a diagnostic challenge. High index of suspicion is paramount for its early diagnoses to prevent orthopedic and cardiac complications. Prompt diagnosis and management is essential to improve on the prognosis of this disease.

Serum Enzyme Profiles Differentiate Five Types of Muscular Dystrophy

Background. Differentiation among types of muscular dystrophy (MD) has remained challenging. In this retrospective study, we sought to develop a methodology for differentiation of MD types using analysis of serum enzyme profiles. Methods. The serum levels of enzymes from 232 patients, including 120 with DMD, 36 with BMD, 36 with FSHD, 46 with LGMD, and 11 with EDMD, were evaluated. Results. The characteristic profiles of serum enzymes facilitated differentiation of these five types of MD. DMD was characterized by simultaneous elevation of ALT, AST, LDH, and ALP; BMD and LGMD were characterized by elevation of ALT, AST, and LDH; and FSHD and EDMD were characterized by a lack of abnormal serum enzyme levels. We further developed discriminant functions to distinguish BMD and LGMD. For LGMD, LGMD2B patients had significantly higher ALP levels than non-LGMD2B patients (98 ± 59 U/L versus 45 ± 9 U/L, resp., p < 0.05). Conclusions. Our approach enabled the determination of MD subtypes using serum enzyme profiles prior to genetic testing, which will increase the chance a mutation will be found in the first gene analyzed.

The nuclear envelope: an intriguing focal point for neurogenetic disease

Mutations in genes encoding nuclear envelope proteins cause a wide range of inherited diseases, many of which are neurological. We review the genetic causes and what little is known about pathogenesis of these nuclear envelopathies that primarily affect striated muscle, peripheral nerve and the central nervous system. We conclude by providing examples of experimental therapeutic approaches to these rare but important neuromuscular diseases.

Distal myopathies

In this article, distal myopathy syndromes are discussed. A discussion of the more traditional distal myopathies is followed by discussion of the myofibrillar myopathies. Other clinically and genetically distinctive distal myopathy syndromes usually based on single or smaller family cohorts are reviewed. Other neuromuscular disorders that are important to recognize are also considered, because they show prominent distal limb weakness.

Emery-Dreifuss muscular dystrophy, laminopathies, and other nuclear envelopathies

The nuclear envelopathies, more frequently known as laminopathies are a rapidly expanding group of human hereditary diseases caused by mutations of genes that encode proteins of the nuclear envelope. The most frequent and best known form is Emery-Dreifuss muscular dystrophy (EDMD), a skeletal myopathy characterized by progressive muscular weakness, joint contractures, and cardiac disease. EMD gene, encoding emerin, causes the X-linked form of EDMD, while LMNA gene encoding lamins A and C, is responsible for autosomal forms, usually with a dominant transmission. In the last years, the spectrum of conditions has been extraordinarily enlarged, from a congenital muscular dystrophy with severe paralytic or rapidly progressive picture due to de novo mutations in LMNA (L-CMD) to a limb-girdle muscular dystrophy with adult onset and much milder weakness (LGMD1B). LMNA has also been involved in a form of isolated cardiomyopathy associated with cardiac conduction disease and in an axonal form of hereditary neuropathy. Identification of this gene has been reported also in a number of non-neuromuscular disorders including lipodystrophy syndromes and a wide spectrum of premature aging syndromes ranging from mandibuloacral dysplasia to restrictive dermopathy. Mutations in other genes implicated in the processing or maturation of nuclear lamins have also been found. The extraordinary complexity of the molecular and pathophysiological mechanisms of these diseases is still not well known and the occurrence of modifying factors or genes is highly suspected. Identification of new genes and investigation of new therapeutic approaches are in progress.

Muscular dystrophies at different ages: metabolic and endocrine alterations

Common metabolic and endocrine alterations exist across a wide range of muscular dystrophies. Skeletal muscle plays an important role in glucose metabolism and is a major participant in different signaling pathways. Therefore, its damage may lead to different metabolic disruptions. Two of the most important metabolic alterations in muscular dystrophies may be insulin resistance and obesity. However, only insulin resistance has been demonstrated in myotonic dystrophy. In addition, endocrine disturbances such as hypogonadism, low levels of testosterone, and growth hormone have been reported. This eventually will result in consequences such as growth failure and delayed puberty in the case of childhood dystrophies. Other consequences may be reduced male fertility, reduced spermatogenesis, and oligospermia, both in childhood as well as in adult muscular dystrophies. These facts all suggest that there is a need for better comprehension of metabolic and endocrine implications for muscular dystrophies with the purpose of developing improved clinical treatments and/or improvements in the quality of life of patients with dystrophy. Therefore, the aim of this paper is to describe the current knowledge about of metabolic and endocrine alterations in diverse types of dystrophinopathies, which will be divided into two groups: childhood and adult dystrophies which have different age of onset.

Mutations of the FHL1 gene cause Emery-Dreifuss muscular dystrophy

Emery-Dreifuss muscular dystrophy (EDMD) is a rare disorder characterized by early joint contractures, muscular dystrophy, and cardiac involvement with conduction defects and arrhythmias. So far, only 35% of EDMD cases are genetically elucidated and associated with EMD or LMNA gene mutations, suggesting the existence of additional major genes. By whole-genome scan, we identified linkage to the Xq26.3 locus containing the FHL1 gene in three informative families belonging to our EMD- and LMNA-negative cohort. Analysis of the FHL1 gene identified seven mutations, in the distal exons of FHL1 in these families, three additional families, and one isolated case, which differently affect the three FHL1 protein isoforms: two missense mutations affecting highly conserved cysteines, one abolishing the termination codon, and four out-of-frame insertions or deletions. The predominant phenotype was characterized by myopathy with scapulo-peroneal and/or axial distribution, as well as joint contractures, and associated with a peculiar cardiac disease characterized by conduction defects, arrhythmias, and hypertrophic cardiomyopathy in all index cases of the seven families. Heterozygous female carriers were either asymptomatic or had cardiac disease and/or mild myopathy. Interestingly, four of the FHL1-mutated male relatives had isolated cardiac disease, and an overt hypertrophic cardiomyopathy was present in two. Expression and functional studies demonstrated that the FHL1 proteins were severely reduced in all tested patients and that this was associated with a severe delay in myotube formation in the two patients for whom myoblasts were available. In conclusion, FHL1 should be considered as a gene associated with the X-linked EDMD phenotype, as well as with hypertrophic cardiomyopathy.

Emery-Dreifuss muscular dystrophy: a novel mutation in the LMNA gene

Described here is the phenotypical expression of a novel LMNA mutation c.1157 G>T in a Czech patient with an early-onset form of Emery-Dreifuss muscular dystrophy. The mutation predicts aberrant splicing. Now 21 years old, the patient has had slowly progressing muscle dystrophy since the age of one and early contractures of elbows. He is the only family member affected. Even though the dystrophy typically affects the heart as well, in the present case these signs are not yet expressed.

Emery-Dreifuss muscular dystrophy

Emery-Dreifuss muscular dystrophy (EDMD) is inherited in an X-linked or autosomal manner. X-linked EDMD is caused by mutations in EMD, which encodes an integral protein of the nuclear envelope inner membrane called emerin. Autosomally inherited EDMD is caused by mutations in LMNA, which encodes A-type nuclear lamins, intermediate filament proteins associated with inner nuclear membrane. Although the causative mutations have been described and mouse models have been created, the pathogenic processes by which mutations in genes encoding nuclear envelope proteins cause striated muscle abnormalities in EDMD remain obscure. Working hypotheses include effects on nuclear structural integrity, increased cellular susceptibility to mechanical stress damage, alterations in gene expression in response to nuclear envelope changes, and effects on cell proliferation and differentiation.

Co-morbidity of Emery-Dreifuss muscular dystrophy and a congenital myasthenic syndrome possibly affecting the phenotype in a large Bedouin kindred

Emery-Dreifuss muscular dystrophy (EDMD) is an X-linked humero-peroneal muscular dystrophy associated with contractures and cardiomyopathy. In a 90 member family, we found 11 affected male individuals, three of whom displayed areflexia and neurogenic electromyographic changes. Muscle biopsy performed in one case demonstrated type grouping suggestive of a neurogenic disorder. These three individuals and another family member, who suffers from mild, static limb weakness but is clinically and genetically unaffected by EDMD showed an abnormal incremental response of over 100% to tetanic stimulation. In contrast, one affected family member showed myopathic features on needle electromyography and no definite pathology in repetitive stimulation studies. The diagnosis of EDMD was established by demonstrating a 1712_1713insTGGGC mutation in the emerin gene. This family apparently expresses co-morbidity of EDMD with an exceptionally mild form of pre-synaptic congenital myasthenic syndrome resembling the Lambert-Eaton myasthenic syndrome (LEMS). The superimposed pre-synaptic disorder may have contributed to the development of the neurogenic features demonstrated in these patients.

Nuclear Lamins: Laminopathies and Their Role in Premature Ageing

It has been demonstrated that nuclear lamins are important proteins in maintaining cellular as well as nuclear integrity, and in maintaining chromatin organization in the nucleus. Moreover, there is growing evidence that lamins play a prominent role in transcriptional control. The family of laminopathies is a fast-growing group of diseases caused by abnormalities in the structure or processing of the lamin A/C ( LMNA) gene. Mutations or incorrect processing cause more than a dozen different inherited diseases, ranging from striated muscular diseases, via fat- and peripheral nerve cell diseases, to progeria. This broad spectrum of diseases can only be explained if the responsible A-type lamin proteins perform multiple functions in normal cells. This review gives an overview of current knowledge on lamin structure and function and all known diseases associated with LMNA abnormalities. Based on the knowledge of the different functions of A-type lamins and associated proteins, explanations for the observed phenotypes are postulated. It is concluded that lamins seem to be key players in, among others, controlling the process of cellular ageing, since disturbance in lamin protein structure gives rise to several forms of premature ageing.

Nuclear envelope, nuclear lamina, and inherited disease

The nuclear envelope is composed of the nuclear membranes, nuclear lamina, and nuclear pore complexes. In recent years, mutations in nuclear-envelope proteins have been shown to cause a surprisingly wide array of inherited diseases. While the mutant proteins are generally expressed in most or all differentiated somatic cells, many mutations cause fairly tissue-specific disorders. Perhaps the most dramatic case is that of mutations in A-type lamins, intermediate filament proteins associated with the inner nuclear membrane. Different mutations in the same lamin proteins have been shown to cause striated muscle diseases, partial lipodystrophy syndromes, a peripheral neuropathy, and disorders with features of severe premature aging. In this review, we summarize fundamental aspects of nuclear envelope structure and function, the inherited diseases caused by mutations in lamins and other nuclear envelope proteins, and possible pathogenic mechanisms.

Nuclear envelope proteins and neuromuscular diseases

Several neuromuscular diseases are caused by mutations in emerin and A-type lamins, proteins of the nuclear envelope. Emery-Dreifuss muscular dystrophy is caused by mutations in emerin (X-linked) or A-type lamins (autosomal dominant). Mutations in A-type lamins also cause limb-girdle muscular dystrophy type 1B, dilated cardiomyopathy with conduction defect, and Charcot-Marie-Tooth disorder type 2B1. They also cause partial lipodystrophy syndromes. The functions of emerin and A-type lamins and the mechanisms of how mutations in these proteins cause tissue-specific diseases are not well understood. The mutated proteins may cause structural damage to cells but may also affect processes such as gene regulation. This review gives an overview of this topic and describes recent advances in identification of disease-causing mutations, studies of cells and tissues from subjects with these diseases, and animal and cell culture models.

Properties of lamin A mutants found in Emery-Dreifuss muscular dystrophy, cardiomyopathy and Dunnigan-type partial lipodystrophy

Autosomal dominant Emery-Dreifuss muscular dystrophy is caused by mutations in the LMNA gene, which encodes lamin A and lamin C. Mutations in this gene also give rise to limb girdle muscular dystrophy type 1B, dilated cardiomyopathy with atrioventricular conduction defect and Dunnigan-type partial lipodystrophy. The properties of the mutant lamins that cause muscular dystrophy, lipodystrophy and dilated cardiomyopathy are not known. We transfected C2C12 myoblasts with cDNA encoding wild-type lamin A and 15 mutant forms found in patients affected by these diseases. Immunofluorescence microscopy showed that four mutants, N195K, E358K, M371K and R386K, could have a dramatically aberrant localization, with decreased nuclear rim staining and formation of intranuclear foci. The distributions of endogenous lamin A/C, lamin B1 and lamin B2 were also altered in cells expressing these four mutants and three of them caused a loss of emerin from the nuclear envelope. In the yeast two-hybrid assay, the 15 lamin A mutants studied interacted with themselves and with wild-type lamin A and lamin B1. Pulse-chase experiments showed no decrease in the stability of several representative lamin A mutants compared with wild-type. These results indicate that some lamin A mutants causing disease can be aberrantly localized, partially disrupt the endogenous lamina and alter emerin localization, whereas others localize normally in transfected cells.

Clinical and genetic aspects of distal myopathies

Although most muscle disorders produce proximal weakness, some myopathies may manifest predominantly or exclusively distal weakness. Although several congenital, inflammatory, or metabolic myopathies may produce mainly distal weakness, there are several distinct entities, typically referred to as distal myopathies. Most of these are inherited conditions. The distal myopathies are rare, but characteristic clinical and histological features aid in their identification. Advances in molecular genetics have led to the identification of the gene lesions responsible for several of these entities and have also expanded our understanding of the genetic relationships of distal myopathies to other inherited disorders of muscle. This review summarizes current knowledge of the clinical and molecular aspects of the distal myopathies.

Intermediate filament-related myopathies

The dynamic and critical role of intermediate filaments in muscle is highlighted by myopathies characterized by aberrant accumulation of intermediate filaments. In some affected patients, mutations in genes encoding intermediate filaments that are expressed in muscle have been confirmed. The importance of intermediate filaments in muscle is further strengthened by murine models in which genetically designed intermediate filament mutations are expressed, leading to progressive skeletal or cardioskeletal myopathy in affected mice. In this article the intermediate filaments expressed in muscle are reviewed, and the clinical and pathologic features of myopathies known to relate to intermediate filaments are described. With the increasing awareness of intermediate filaments in muscle and the rapid advances in genetic investigation, it is likely that the list of intermediate filament-related myopathies will expand.

Familial mydriasis, cardiac arrhythmia, respiratory failure, muscular weakness and hypohidrosis

OBJECTIVES

To describe a family with some sort of progressive autonomic failure in one generation (2 affected of a sibship of 7 sisters). The main features were: mydriasis, cardiac arrhythmia, cardiomegaly, hypohidrosis, respiratory failure, and muscular weakness.

METHODS

Pupillometry, evaporimetry, and isokinetic power measurements were carried out.

RESULTS

The autonomic dysfunction pattern (mainly cardiac abnormalities, mydriasis) seems to differ somewhat from that of progressive autonomic failure (Shy-Drager syndrome). "Lewy body-like" inclusions were present, in particular in substantia nigra, but also in locus ceruleus and raphe nuclei (cell loss only in locus ceruleus). There were no oligodendroglial, cytoplasmatic inclusions, apparently a marker in multiple system atrophy. Proper Lewy bodies were also present. Differences seemed to prevail vs the Shy-Drager syndrome. Various traits: muscular weakness pattern (e.g. preferential peroneal distribution), minor elbow contractures, and arrhythmia were reminiscent of Emery-Dreifuss muscle dystrophy (E-D). Distinguishing features included: hereditary pattern, mydriasis, and hypohidrosis.

CONCLUSION

Conceivably, this disorder is close to, but still not identical with E-D.

Emery-Dreifuss muscular dystrophy: anatomical-clinical correlation (case report)

We report on a man that had weakness of humeroperoneal distribution associated with limited range of motion of the cervical spine and elbows since he was 5 years old. At age 26 he developed tachycardia episodes. A complex arrhythmia was discovered, and a nodal ablation was done with a cardiac pacemaker implanted. The patient had an arrhythmia and sudden death followed this. Emery-Dreifuss muscular dystrophy is a rare recessive X-linked muscular disorder where mixed patterns in electromyography and muscle histology (neurogenic and/or myopathic) have caused nosological confusion. The autopsy findings are here described and correlated to the clinical features in an attempt to better understand the ambiguous findings concerning the process etiology.

Diagnosis of pediatric neuromuscular disorders in the era of DNA analysis

Extraordinary breakthroughs in the molecular pathogenesis of muscle and nerve disease have resulted in an evolving genetic classification of neuromuscular disorders and the development of new diagnostic methods. This remarkable progress has introduced new genetic tests and has changed the indications for use of certain invasive diagnostic procedures in the evaluation of children with presumed disorders of the motor unit. In this review, we present the current diagnostic approach to the more common neuromuscular diseases of infancy and childhood and define the diagnostic role of muscle biopsy and pediatric electromyography/nerve conduction studies in the era of genetic analysis.

Nuclear envelope proteins and associated diseases

There is a growing body of evidence in favour of the presence of human diseases caused by mutations in genes that encode the nuclear envelope proteins emerin and lamin A/C (lamin A and C are alternatively spliced variants of the same gene). Emerin deficiency results in X-linked Emery-Dreifuss muscular dystrophy (EDMD). Lamin A/C mutations cause the autosomal-dominant form of EDMD, limb-girdle muscular dystrophy with atrioventricular conduction disturbances (type 1B), hypertrophic cardiomyopathy and Dunnigan-type familial partial lipodystrophy. In the targeted mouse model of lamin A gene deficiency, loss of lamin A/C is associated with mislocalization of emerin. Thus, one plausible pathomechanism for EDMD, limb-girdle muscular dystrophy type 1B, hypertrophic cardiomyopathy and familial partial lipodystrophy is the presence of specific abnormalities of the nuclear envelope. Therefore, a group of markedly heterogeneous disorders can be classified as 'nuclear envelopathies'. The present review summarizes recent findings on nuclear envelope proteins and diseases.

Emery-Dreifuss muscular dystrophy - a 40 year retrospective

Emery-Dreifuss muscular dystrophy (EDMD) was delineated as a separate form of muscular dystrophy nearly 40 years ago, based on the distinctive clinical features of early contractures and humero-peroneal weakness, and cardiac conduction defects. The gene, STA at Xq28, for the commoner X-linked EDMD encodes a 34 kD nuclear membrane protein designated 'emerin', and in almost all cases on immunostaining is absent in muscle, skin fibroblasts, leucocytes and even exfoliative buccal cells, and a mosaic pattern in female carriers. The gene, LMNA at 1q21, for the autosomal dominant Emery-Dreifuss muscular dystrophy encodes other nuclear membrane proteins, lamins A/C. The diagnosis (at present) depends on mutation analysis rather than protein immunohistochemistry. It is still not at all clear how defects in these nuclear membrane proteins are related to the phenotype, even less clear that LMNA mutations can also be associated with familial dilated cardiomyopathy with no weakness, and even familial partial lipodystrophy with diabetes mellitus and coronary heart disease! What began as clinical studies in a relatively rare form of dystrophy has progressed to detailed research into the functions of nuclear membrane proteins particularly in regard to various forms of heart disease.

Mutation analysis in Emery-Dreifuss muscular dystrophy

The purpose of this study was to search for STA gene defects in three families with clinically typical Emery-Dreifuss muscular dystrophy. Emery-Dreifuss is an X-linked muscular dystrophy with humeroperoneal weakness and life-threatening, but treatable, cardiac abnormalities in male patients and in female carriers. The defect is in the gene coding for emerin, a 254 amino acid protein of unknown function. Complementary and genomic DNA from T lymphocytes from the reported patients and their family members were amplified, cloned, and sequenced. A novel mutation, a 26 base-pair deletion in three brothers and a carrier mother, was detected in one family. A splicing mutation with one base pair insertion and a five base-pair deletion, which have been described previously, were found in the second and third families, respectively. The additional novel mutation detected and the findings of three different mutations in these three families support the idea of genetic heterogeneity of Emery-Dreifuss muscular dystrophy with different mutations in different families.

Intracellular trafficking of emerin, the Emery-Dreifuss muscular dystrophy protein

Emerin is an integral protein of the inner nuclear membrane that is mutated or not expressed in patients with Emery-Dreifuss muscular dystrophy. Confocal immunofluorescence microscopy studies of the intracellular targeting of truncated forms of emerin, some of which are found in patients with Emery-Dreifuss muscular dystrophy, show that the nucleoplasmic, amino-terminal domain is necessary and sufficient for nuclear retention. When this domain is fused to a transmembrane segment of an integral membrane protein of the ER/plasma membrane, the chimeric protein is localized in the inner nuclear membrane. The transmembrane segment of emerin is not targeted to the inner nuclear membrane. Fluorescence photobleaching experiments of emerin fused to green fluorescent protein demonstrate that the diffusional mobility (D) of emerin is decreased in the inner nuclear membrane (D=0.10+/-0.01 microm2/second) compared to the ER membrane (D=0.32+/-0.01 microm2/second). This is in agreement with a model where integral proteins reach the inner nuclear membrane by lateral diffusion and are retained there by association with nucleoplasmic components. Some overexpressed emerin-green fluorescent protein also reaches the plasma membrane of transfected cells, where its diffusion is similar to that in the inner nuclear membrane, suggesting that emerin may also associate with non-nuclear structures.

Emerin and cardiomyopathy in Emery-Dreifuss muscular dystrophy

Emery-Dreifuss muscular dystrophy (EDMD) is an inherited disorder characterized by the clinical triad of life-threatening progressive cardiomyopathy with conduction defect, early onset joint contractures and slow progressive muscle weakness in scapulo-humero-peroneal distribution. Cardiomyopathy in EDMD is usually noticed after the second to third decade of life, and becomes worse with age. Permanent auricular paralysis occurs frequently and is considered a hallmark of EDMD cardiomyopathy. Cardiac involvement may also occur in female carriers. In autopsy cases, enlargement of the atria with remarkable thinning have been observed. Identification of the gene responsible for X-linked EDMD (X-EDMD) and the protein product, emerin, provided a diagnostic clue for EDMD. Since the emerin gene is rather small, the entire sequence can easily be surveyed. Western blot and immunohistochemistry show an absence of emerin in muscle and skin tissues and oral exfoliating cells in male patients with X-EDMD, and a reduction of the protein content with a mosaic expression pattern in female carriers. Emerin anchors at the inner nuclear membrane of cardiac, skeletal and smooth muscles, and interacts with lamins and nucleoplasm, thereby possibly maintaining the mechanical stability of the nuclear membrane of muscle cells that shows rigorous contraction/relaxation. More recently, positive emerin staining at the cardiac demosomes and fasciae adherentes was noticed in addition to the specific localization at the inner nuclear membrane. This localization implies a physiological role for the protein in cardiac conduction.

Cardiac manifestations of congenital fiber-type disproportion myopathy

Cardiac involvement has not been a reported feature of congenital fiber-type disproportion myopathy. We describe two children, aged 13 years and 1 year, respectively, who presented with serious cardiac symptomatology in conjunction with congenital fiber-type disproportion. One child developed dilated cardiomyopathy and medically intractable congestive heart failure necessitating cardiac transplantation at the age of 13 years. The second (unrelated) child developed atrial fibrillation with rapid atrioventricular conduction requiring treatment with digoxin. Skeletal muscle biopsy findings in both children showed congenital fiber-type disproportion with no evidence of a structural, dystrophic, or metabolic myopathy. Adenosine triphosphatase (ATPase) reacted sections showed type I hypotrophy with a predominance of type I fibers, confirmed by histogram analysis. Examination of the heart from patient 1 at the time of transplantation confirmed dilated cardiomyopathy with hypertrophic myocardiocytes. Although cardiomyopathy is commonly associated with other childhood myopathies, to our knowledge it has not been a feature in reported cases of congenital fiber-type disproportion. We recommend close cardiac assessment, with annual electrocardiograms, of children with congenital fiber-type disproportion.

Identification of a new locus for a peculiar form of congenital muscular dystrophy with early rigidity of the spine, on chromosome 1p35-36

Classical congenital muscular dystrophies (CMDs) are autosomal recessive neuromuscular disorders characterized by early onset of hypotonia and weakness, atrophy of limbs and trunk muscles, contractures, and dystrophic changes in the muscle biopsy. So far, only one gene, LAMA2 (6q2), which encodes the laminin alpha2 chain (or merosin), has been identified in these disorders. Mutations in LAMA2 cause CMD with complete or partial merosin deficiency, detectable by immunocytochemistry on muscle biopsies, and account for approximately 50% of CMD cases. In a large consanguineous family (11 siblings) comprising three children affected by CMD without merosin deficiency, we undertook a genomewide search by homozygosity mapping and analyzed 380 microsatellite markers. The affected children were homozygous for several markers on chromosome 1p35-36. We identified two additional consanguineous families with affected children who also showed linkage to this locus. A maximum cumulative LOD score of 4.48, at a recombination fraction of .00, was obtained with D1S2885. A consistent feature in these three families was the presence of early rigidity of the spine, scoliosis, and reduced vital capacity, as found in rigid-spine syndrome (RSS). This study is the first description of a locus for a merosin-positive CMD and will help to better define the nosology of RSS.

Nondystrophinopathic muscular dystrophies including myotonic dystrophy

The spectacular progress concerning dystrophin and its pathology, the dystrophinopathies, has led to a somewhat arbitrarily separated heterogeneous group of nondystrophinopathic muscular dystrophies that currently comprise the Emery-Dreifuss type, the nosologically heterogeneous autosomal-recessive limb-girdle muscular dystrophy, the severe childhood autosomal-recessive muscular dystrophy, the merosin-positive and -negative congenital muscular dystrophies, the autosomal-recessive distal muscular dystrophy of Miyoshi, the facio-scapulo-humeral muscular dystrophy, and myotonic dystrophy, both the adult and neonatal variants. Deficiencies of adhalin in a particular form of limb-girdle muscular dystrophy, and of merosin in a particular form of congenital muscular dystrophy as well as the newly discovered principle of abnormal tri-nucleotide repeats in myotonic dystrophy are evidence of progress that has also amplified the notion of the dystrophinopathies that the protein-deficient muscular dystrophies can now be considered examples of contributions of the dystrophin-glycoprotein complex across the muscle fiber plasma membrane.

A novel emerin mutation in a Japanese patient with Emery-Dreifuss muscular dystrophy

Sequencing of the STA gene in a patient with Emery-Dreifuss muscular dystrophy showed a 1-bp deletion of C at nucleotide 672 or 673. This deletion causes a frameshift, changing the amino acid sequence (amino acids 206-235) and generating an early stop codon.

A newly recognized autosomal dominant limb girdle muscular dystrophy with cardiac involvement

Sixty-five members of three families with limb girdle muscular dystrophy (LGMD) underwent neurological, cardiological, and ancillary investigations. Thirty-five individuals were diagnosed as having slowly progressive autosomal dominant LGMD. Symmetrical weakness started in the proximal lower limb muscles, and gradually upper limb muscles also became affected. Early contractures of the spine were absent. Contractures of elbows and Achilles tendons were either minimal or late. Serum creatine kinase activity was normal to moderately elevated. Electromyogram and muscle biopsy were consistent with a mild muscular dystrophy. Cardiological abnormalities, found in more than one-half the patients, included dysrhythmias and atrioventricular (AV) conduction disturbances presenting as bradycardia, syncopal attacks necessitating pacemaker implantation, and sudden cardiac death. There was a significant relation between the severity of AV conduction disturbances and age. In nearly all patients, neuromuscular symptomatology preceded cardiological involvement. The early recognition of this previously not described, autosomal dominant LGMD with life-threatening cardiac involvement offers an opportunity for therapeutic intervention.

Chromosome 12-linked autosomal dominant scapuloperoneal muscular dystrophy

Scapuloperoneal syndromes are characterized by their distribution of muscle weakness and wasting. The reported pattern of inheritance has been variable. Both neurogenic and myopathic forms of autosomally dominantly inherited scapuloperoneal syndrome have been described. It has been suggested that these are variants of other neuromuscular diseases. We examined 44 members from a family with 14 members affected with a scapuloperoneal syndrome. Physiological and histological analysis implied that this condition is predominantly myopathic. Linkage analysis was done to confirm the genetic etiology of the disease in this family and to evaluate the possibility that it is a allelic variant of other neuromuscular diseases. Genetic analysis demonstrated linkage of the disease to chromosome 12, which makes it genetically distinct from other loci known to cause neuromuscular disease. Muscle fibers with hyaline desmin-containing cytoplasmic inclusions in combination with focal myopathic changes may be a disease-specific morphological marker of the disease.

Diagnosis in neuromuscular diseases

The diagnosis of neuromuscular diseases can be challenging and successful in the majority of patients, due to advancements in electrophysiology, muscle and nerve biopsy immunohistochemistry, and cytogenetics. This article reviews diverse topics, highlighting these recent achievements, with an emphasis on how they affect the clinical and laboratory diagnosis of specific neuromuscular disorders.

Expression of growth associated protein 43 and neural cell adhesion molecule in congenital fibre type disproportion with interstitial myositis

We report on the expression of growth associated protein (GAP)43 and neural cell adhesion molecule (NCAM) in congenital fibre type disproportion (CFTD) with myopathological additional signs of interstitial myositis. We assume that sarcolemmal GAP43 in developmental disordered myocytes plays a role in maintenance of growth morphology. In muscular dystrophy light microscopical evaluation reveals no GAP43 immunoreactivity in regenerating fibres. The expression of GAP43 seems to be a characteristic feature of CFTD. The expression of NCAM, particularly in the sarcolemma of small muscle fibres of CFTD, indicates a functional state of permanent partial denervation. Whether the steroid-responsive interstitial myositis is pathogenetically related to CFTD or a coincidental inflammation is not known. Because of the clinical and myopathological data the differential diagnosis of Emery-Dreifuss muscular dystrophy is considered.

The rigid spine syndrome: a vacuolar variant

The rigid spine syndrome encompasses a number of disorders. We report 7 males and 2 females with this phenotype and a single, not previously reported, nosology. The salient muscle histological features were autophagic vacuoles, vacuoles containing capillaries, muscle spindle swelling, and type I fiber predominance. Disease onset was before age 6 years in all patients. Inheritance was probably autosomal recessive as siblings were affected in two families. Pulmonary function tests showed severely restricted ventilation, 3 patients required nocturnal ventilatory assistance, 2 patients had cor pulmonale, and mitral valve abnormalities were common. Serum CK levels were moderately elevated. EMG studies showed evidence of an active, chronic myopathy. The mean motor unit potential duration was statistically significantly shorter compared to controls in the triceps and anterior tibial muscles. Single fiber EMG "jitter" and evoked potential studies were normal.

Expression and localization of dystrophin in human cardiac Purkinje fibers

BACKGROUND

Mutations in the dystrophin gene produce clinical manifestations of disease in heart, brain, and skeletal muscle in patients with Duchenne and Beckers muscular dystrophy (DMD/BMD). Conduction disturbances and heart block contribute to cardiac decompensation in these patients, which suggests an important role for dystrophia in the cardiac conduction system. We therefore examined the messenger RNA (mRNA) expression and protein localization of dystrophin in normal human cardiac Purkinje fibers.

METHODS AND RESULTS

Polymerase chain reaction amplification of isolated Purkinje fiber complementary DNA identified several alternatively spliced mRNA transcripts encoding for carboxy-terminal isoforms of the dystrophin protein. The predominant mRNA transcript detected was a splice form previously detected in the brain. Antipeptide antibodies specific for a carboxy-terminal dystrophin sequence were used for Western blot analysis and immunocytochemical localization. These antisera detect approximately 400,000-d immunoreactive band or bands on Western blot in normal heart and Purkinje fibers but not in DMD heart. Immunocytochemical staining showed that dystrophin was localized to the membrane surface of the Purkinje fiber.

CONCLUSIONS

These results suggest that dystrophin may be an important molecule for membrane function in the Purkinje conduction system of the heart and support the hypothesis that defective dystrophin expression contributes to the cardiac conduction disturbances seen in DMD/BMD:

Atrial Paralysis in a Patient with Emery-Dreifuss Muscular Dystrophy

Emery-Dreifuss disease is a benign X-linked muscular dystrophy characterized by a distinct pattern of muscle weakness, which is of insidious onset and slow progression. It is associated with atrial paralysis that results in sudden death in early adulthood if left untreated. The authors report the documentation of electrical and mechanical silence confined to the atria in a patient with this disease. Electrocardiography and electrophysiological study document the absence of electrical atrial activity, and inability to pace the atria. Hemodynamic studies demonstrate the absence of A waves, and angiography revealed immobility of the atria. This patient has done well following the institution of permanent ventricular pacing. His brother, who also had muscular dystrophy, died a sudden cardiac death at the age of 29 after refusing medical intervention. Emery-Dreifuss muscular dystrophy is particularly worthy of recognition because of the preventable occurrence of sudden death in young patients with an otherwise excellent prognosis. Permanent ventricular pacing is indicated.

Multipoint linkage mapping of the Emery-Dreifuss muscular dystrophy gene

The clinical features to establish the diagnosis of X-linked Emery-Dreifuss muscular dystrophy (EMD) were recently redefined at the European EMD workshop in Baarn 1991. These criteria were used to select families from the literature and two new families for linkage analysis with the DNA markers F9, DX52, DXS15, F8C and DXS115. Recombinations are observed with the DNA markers F9, DXS52 and DXS15. No recombinations were found with F8C and DXS115. Multipoint linkage analysis indicates with a maximum location score of 73.9 that the EMD locus maps very close to F8C.

Progression of cardiac disease in Emery-Dreifuss muscular dystrophy

Emery-Dreifuss muscular dystrophy (EDMD) is a rare X-linked muscular dystrophy characterized by early contractures, progressive muscle weakness, and atrial arrhythmias. Recent reports suggest that there may be additional cardiac problems in affected males and that carrier females may also show ECG abnormalities. We restudied two large families with EDMD in order to determine the extent of these problems. We examined 10 affected males and interviewed 2 others. The 3 affected males less than 20 years old had no ECG changes. All affected men of 35 years or older had arrhythmias. One had more severe arrhythmias when asleep, indicating the usefulness of continuous 24-h ECG monitoring in the evaluation of males affected with EDMD. Two required pacemakers, 4 had already had a pacemaker placed, and 4 other affected men with pacemakers had died prior to this study. One affected man with a pacemaker developed ventricular bigeminy and another developed congestive heart failure. Thus of 10 affected males with pacemakers, 6 had additional cardiac symptoms and 4 have died. Males with EDMD may survive longer with a ventricular pacemaker, but this may increase the likelihood that they will develop cardiomyopathy and ventricular arrhythmias. Of 34 carrier females examined, 6 had arrhythmias typical of EDMD. Two required a pacemaker. The risk of arrhythmia increased with age. Results from one family should be extrapolated to another with caution, as there appears to be significant interfamilial variation. We suggest careful cardiologic follow-up of EDMD patients and regular cardiac evaluations for older carrier females.

Becker muscular dystrophy or spinal muscular atrophy?--Dystrophin studies resolve conflicting results of electromyography and muscle biopsy

We studied a 29-year-old man with slowly progressive proximal leg weakness, calf hypertrophy, and high serum levels of creatine kinase activity. Clinically, it was not possible to identify his as a sporadic instance of Becker muscular dystrophy (BMD) or one of spinal muscular atrophy. The problem arose because electromyography and elevated creatine kinase suggested a myopathy whereas changes in the muscle biopsy resembled a neurogenic disorder. The diagnosis of BMD was made by DNA analysis which detected a deletion at Xp21 and by immunoelectrophoresis and immunohistochemical tests that identified an abnormal form of gene product, dystrophin. These studies were important for genetic counselling, identifying an X-linked disease instead of one that is autosomal recessive.

Emery-Dreifuss muscular dystrophy

Emery-Dreifuss syndrome is a rare form of muscular dystrophy associated with cardiac complications that lead to sudden death. The disorder and its potential anaesthetic implications in the management of a patient who presented for orthopaedic surgery is described.

Cardiac transplantation in female Emery-Dreifuss muscular dystrophy

A young woman with humeroperoneal muscular dystrophy and contractures received a heart transplant for a severe dilated cardiomyopathy. Cardiac histopathology consisted of myocyte hypertrophy, interstitial fibrosis, and nuclear hyperchromaticity without mitochondrial abnormalities. Myopathy and heart disease were not clinically evident in her family, although three relatives had unexplained shortened Achilles tendons without weakness. Tendon contractures may be a partial expression of this myopathic disorder, suggesting an autosomal dominant inheritance with variable penetrance. A muscular dystrophy clinically similar to that of the Emery-Dreifuss (EDMD) type can thus occur in women. Rather than the cardiac arrhythmias typical of EDMD, a dilated cardiomyopathy may occur and present with severe congestive heart failure. This is the first report of cardiac transplantation in such a case.

Facioscapulohumeral muscular dystrophy: evidence for selective, genetic electrophysiologic cardiac involvement

Facioscapulohumeral muscular dystrophy is an autosomal dominant disorder with an incidence of 3 to 10 cases per million. The only type of cardiac involvement ascribed to this neuromuscular disorder is a unique form of heart disease--permanent atrial paralysis. However, reported cases of facioscapulohumeral muscular dystrophy probably represented instead what is now recognized as phenotypically similar Emery-Dreifuss dystrophy. Cardiac involvement, therefore, has not been convincingly reported in facioscapulohumeral muscular dystrophy, but because of the clinical similarity of that disorder to Emery-Dreifuss dystrophy and its genetic variants, a prospective investigation of the electrophysiologic properties of the atria and atrioventricular (AV) node and infranodal conduction was undertaken in 30 rigorously documented cases of facioscapulohumeral muscular dystrophy. All patients had a 12 lead surface electrocardiogram (ECG), 22 had a 24 h ambulatory ECG, 15 patients had two-dimensional echocardiographic/Doppler studies and 10 patients underwent 12 intracardiac electrophysiologic investigations. Left atrial, right atrial or biatrial P wave abnormalities were present in 60% of the surface ECGs. Evidence of abnormal AV node or infranodal conduction was present on intracardiac electrophysiologic study or surface ECG in 27% of patients. Atrial flutter or fibrillation was induced by single atrial extra stimuli in 10 of the 12 intracardiac electrophysiologic studies. Sinus node function was abnormal in three patients. This investigation provides the first secure evidence of cardiac involvement in facioscapulohumeral muscular dystrophy. The involvement is represented by relatively high susceptibility to induced atrial flutter or fibrillation during electrophysiologic study, together with less frequent evidence of abnormal sinus node function and abnormal AV node or infranodal conduction.(ABSTRACT TRUNCATED AT 250 WORDS)

Emery-Dreifuss syndrome

Emery-Dreifuss muscular dystrophy is characterised by the triad of (1) early contractures of the elbows, Achilles tendons, and postcervical muscles; (2) slowly progressive muscle wasting and weakness with a humeroperoneal distribution in the early stages; and (3) a cardiomyopathy usually presenting as heart block. The early recognition of the condition is essential because the insertion of a cardiac pacemaker can be life saving. The disorder is usually inherited as an X linked recessive trait (linked to DNA markers around Xq28). However, occasionally it can be inherited as an autosomal dominant trait and there is an indication that this and the X linked form may in some cases have a neurogenic basis. For these reasons it has recently been proposed that the appellation 'Emery-Dreifuss syndrome' be used for this triad of symptoms and signs.