What's new in neuromuscular disorders? The congenital myopathies.

The congenital myopathies are a heterogeneous group of early-onset neuromuscular conditions with characteristic findings on muscle biopsy, comprising central core disease, minicore myopathy (multi-minicore disease), nemaline myopathy and myotubular myopathy. Recent years have seen genetic resolution of a proportion of these conditions. The following review summarizes recent genetic findings in the congenital myopathies and outlines implications for our understanding of their pathophysiological basis and their relation to other neuromuscular disorders.     

Muscle MRI in pediatrics: clinical,pathological and genetic correlation

Pediatric myopathies comprise a very heterogeneous group of disorders that may develop at different ages and affect different muscle groups. Its diagnosis is sometimes difficult and must be confirmed by muscle biopsy and/or genetic analysis. In recent years, muscle involvement patterns observed on MRI have become a valuable tool, aiding clinical diagnosis and enriching pathological and genetic assessments. We selected eight myopathy cases from our institutional database in which the pattern of muscle involvement observed on MRI was almost pathognomonic and could therefore contribute to establishing diagnosis. Muscle biopsy, genetic diagnosis or both confirmed all cases.     

肌肉、周围神经与皮肤病理检查对儿童神经肌肉病的诊断价值

目的 探讨肌肉、周围神经与皮肤活检在儿童神经肌肉病诊断中的价值。方法 对1999年1月至2004年12月在我科接受肌肉、周围神经与皮肤活检术患儿的临床资料进行回顾性分析。结果 102例患儿中82例接受肌肉活检,33例明确诊断,包括肌营养不良13例,炎症性肌肉病4例,先天性中央核肌肉病2例,空泡性肌肉病1例,线粒体肌肉病8例,脂肪累积性肌肉病1例,糖原累积性肌肉病1例,脊肌萎缩症3例。25例为非特异肌肉病理改变。24例肌肉活检未见异常。23例接受腓肠神经活检,9例诊断为遗传性运动感觉神经病,1例为异染性脑白质营养不良伴周围神经受累,11例为非特异性周围神经髓鞘或轴索病变,2例未见异常。8例接受皮肤活检,2例诊断为神经元蜡样质脂褐质沉积症,1例为婴儿神经轴索营养不良,1例为空泡性溶酶体病,4例皮肤活检未见异常。结论 肌肉、周围神经与皮肤活检对明确儿童神经肌肉病的诊断具有重要价值。     

先天性肌型比例失调的诊疗进展

先天性肌型比例失调是一种罕见的先天性肌病.临床表现为儿童早期起病的相对静止的全身肌无力,伴或不伴眼球运动障碍、面肌无力、吞咽障碍、呼吸肌无力等.确诊主要依据特征性肌肉病理改变,即Ⅰ型肌纤维显著小于Ⅱ型且不伴有其他特异性改变.关于此病能否作为独立的临床诊断一直存有争议.但近年来许多致病基因陆续被发现,如TPM3、ACTA1、RYR1等.因此,目前大多数学者仍支持保留先天性肌型比例失调的临床诊断.该文主要就先天性肌型比例失调的临床、病理、基因诊断、基因型和表型相关性及治疗进展进行综述.     

A short protocol for muscle MRI in children with muscular dystrophies

The use of muscle magnetic resonance imaging in patients with muscular dystrophies or congenital myopathies has been limited. We describe the development of a short protocol to be used in young patients with neuromuscular disorders. The protocol includes transverse T1-weighted spin echo sequence images of thighs and calves. The total scanning time is less than 30 minutes, and can be easily applied to patients over the age of 4 years without any need for sedation. Although only the leg muscles are imaged, the images obtained can still help to identify specific patterns of muscle involvement and provide additional help in the differential diagnosis of muscle disorders with overlapping clinical features.     

Myopathic skeletal muscle fiber abnormalities in cardiomyopathies of childhood

Skeletal muscle fibers isolated from 50 muscle specimens from 10 children with cardiomyopathy of unknown cause are compared to those from 18 specimens from 5 patients with skeletal muscle myopathies, 45 specimens from 18 patients with congenital heart disease, and 15 specimens from 7 patients with no genetic, chromosomal, or cardiac disease. Muscle fibers from the myopathy specimens show increased nuclei/mm of fiber and increased nuclei/mm/micron of diameter (R value), as well as reduced surface area and volume of cytoplasm per nucleus, compared to control values. The values for cardiomyopathy deviate from normal in the same way as, but to a lesser degree than, those for myopathy--namely, in this material, diseases with cardiomyopathy tend also to produce mild myopathy. Since cardiac and skeletal muscle pathologic findings have not been adequately studied for the majority of the approximately 50 genetic disorders causing cardiomyopathy or otherwise affecting cardiac function described to date, the data indicate primarily that skeletal muscle biopsy will undoubtedly be more useful in cardiomyopathic disorders when the appropriate correlative studies of cardiac and skeletal muscle in such diseases have been done. Because larger biopsy specimens can be obtained, skeletal muscle merits further exploitation in biochemical research on basic mechanisms of disorders causing cardiomyopathy.     

Myopathic Skeletal Muscle Fiber Abnormalities in Cardiomyopathies of Childhood

Skeletal muscle fibers isolated from 50 muscle specimens from 10 children with cardiomyopathy of unknown cause are compared to those from 18 specimens from 5 patients with skeletal muscle myopathies, 45 specimens from 18 patients with congenital heart disease, and 15 specimens from 7 patients with no genetic, chromosomal, or cardiac disease. Muscle fibers from the myopathy specimens show increased nucleilmm of fiber and increased nucleilmm/µm of diameter (R value), as well as reduced surface area and volume of cytoplasm per nucleus, compared to control values. The values for cardiomyopathy deviate from normal in the same way as, but to a lesser degree than, those for myopathy—namely, in this material, diseases with cardiomyopathy tend also to produce mild myopathy. Since cardiac and skeletal muscle pathologic findings have not been adequately studied for the majority of the approximately 50 genetic disorders causing cardiomyopathy or otherwise affecting cardiac function described to date, the data indicate primarily that skeletal muscle biopsy will undoubtedly be more useful in cardiomyopathic disorders when the appropriate correlative studies of cardiac and skeletal muscle in such diseases have been done. Because larger biopsy specimens can be obtained, skeletal muscle merits further exploitation in biochemical research on basic mechanisms of disorders causing cardiomyopathy.     

NON-DYSTROPHIC, MYOGENIC MYOPATHIES WITH ONSET IN INFANCY OR CHILDHOOD

ABSTRACT. Some "congenital stationary muscle diseases" and some myopathies with known metabolic or endocrine background are reviewed. The clinical picture is described as well as the histological picture in the muscle, the diagnostic and differential diagnostic considerations and procedures, and–when available–the treatment.     

Inherited neuromuscular disorders: pathway to diagnosis

Muscle weakness in childhood can be caused by a lesion at any point extending from the motor cortex, brainstem and spinal cord to the anterior horn cell, peripheral nerve, neuromuscular junction and muscle. A comprehensive history and physical examination is essential to aid classification of the neuromuscular disorder and direct gene testing. The more common disorders such as spinal muscular atrophy, Duchenne muscular dystrophy, myotonic dystrophy and facioscapulohumeral dystrophy may be diagnosed on direct gene testing based on the history and clinical examination. The congenital myopathies are classified based on structural abnormalities on muscle biopsy, while protein abnormalities on immunohistochemistry and immunoblotting aid classification of the muscular dystrophies. In this review, we provide an approach to diagnosis of a child with weakness, with a focus on the inherited neuromuscular disorders, and the features on history, examination and investigation that help to distinguish between them.     

Mutation studies in X-linked myotubular myopathy in three Indian families

Congenital myopathies are a group of genetic disorders characterized by generalised muscle hypotonia and weakness of varying severity. They are distinct entities and do not include muscular dystrophies, metabolic myopathies and mitochondrial disorders. Myotubular myopathy is a rare sub type within this group of disorders. Clinical differentiation of the various types is difficult and requires muscle biopsy with histopathological and immunohistochemical studies for specific diagnosis. Gene studies are a prerequisite for genetic counseling adn prenatal diagnosis. Here presented three cases of X-linked myotubular myopathy in three Indian families where the diagnosis was established by mutation analysis in the MTM1 gene in all, and supported his histopathology in two. All three families had history of previous male neontal deaths with similar complaints. Molecular analysis revealed hemizygous mutations in the MTM1 gene including c.1261-10A>G in case, 1, c.70C>T (R24X) in case 2, and a previously unreported mutation, c.924_926delCTT(p. F308del), in case 3. Genetic counseling was performed regarding the X-linked inheritance, their 50% risk of recurrence in boys in subsequent pregnancies, and a feasibility of prenatal diagnosis. This is the first report of cases of X-linked Myotubular myopathy from India.     

Congenital Myopathies

About forty different congenital myopathies (CM) are defined by clinical and morphological criteria. Classical types like central core disease, centronuclear myopathy, and nemaline/rod myopathy are now well established and recognized as neuromuscular conditions. Clinical subtypes as infantile, juvenile, and adult forms have been recognized in several CM. Not infrequently, different disease-specific morphological features may occur in muscle tissue of the same patient combined. Other CM are marked by aggregates of desmin filaments indicating the importance of recent immunohistochemical techniques. Modern myopathological techniques enabled nosological separation of CM, immunohistochemistry, actually, may usher in a new period of research in and understanding of CM. However, application of molecular genetic and molecular biological methods to CM may clarify still unsolved aspects of gene localisation for which the hereditary nature of many CM is particularly conducive, aspects of heterogeneity versus homogeneity of certain CM or clinical variants, of prenatal diagnosis of CM, of pathogenetic and nosological significance of muscle fiber proteins in CM, and of a new nosological classification of CM.     

Congenital diarrhoea

Congenital diarrhoea of heterogenic etiology is a rare cause of chronic diarrhoea. Characteristic features are: onset in the first weeks of life, life-threatening severe dehydratation and electrolyte disorders leading to a necessity of long-term parenteral nutrition. The clinical onset may be delayed and the degree of diarrhoea may be modest, making the diagnosis difficult. The main causes of congenital diarrhoea such as intestine electrolytes, carbohydrates, lipid and protein transport disorders and congenital enzymatic deficiencies, enterocyte polarization disorders, hormonal, immunological, metabolic, genetic and congenital anatomic disorders are presented in the paper. Some of them, such as: microvillus inclusion disease, tufting enteropathy, intestinal anedocrynosis, IPEX syndrome (immunodysregulation polyendocrinopathy enteropathy X-linked syndrome) have been described recently. One of the basic investigations, when congenital diarrhea is suspected, is general examination of the stool, its electrolyte concentration and serum electrolytes and blood gas analysis. Often, small bowel biopsy with histological examination (with the use of electronic microscopy and PAS staining) is indicated. In some cases molecular examination is possible and indicated. In differential diagnosis other, more frequent causes of chronic diarrhea of infancy, have to be excluded. In most of the cases of congenital diarrhoea there is no casual treatment available - usually long-term parenteral nutrition is necessary.     

Myopathies in endocrine disorders

Disorders of the thyroid gland, the parathyroids and adrenals may cause muscle dysfunction. The following features seem to be typical for most of these endocrine myopathies: 1. Usually proximal limb muscles, i.e. pelvic and/or shoulder girdle musculatur, are involved. - 2. Even in cases with severe clinical symptoms morphological abnormalities of the muscles are relatively mild, suggesting that these disorders are mainly functional ones. - 3. The myopathies usually resolve completely with effective treatment of the underlying endocrine disorder. - The pathogenetic mechanisms involved largely remain uncertain. Objective myopathy may be one of the early and dominant features of disorders of the thyroid gland, the parathyroids and adrenals. These endocrine abnormalities have therefore to be taken into account in the differential diagnosis of muscle disorders in childhood.     

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??Abstract??Hereditary neuromuscular disease is a group of diseases clinically manifested as motor function disorders and hereditary myopathies??peripheral neuropathies??motor neuropathies as well as neuromuscular junction diseases are mainly included.With the rapid development of genetic testing technology??genes related to hereditary neuromuscular diseases and novel mutations are continued to discover?? providing a reliable basis for genetic diagnosis??genetic counseling and prenatal diagnosis.Taking medical history in detail and doing physical examination completely as well as laboratory examinations??such as serum chemical analysis??muscle imaging studies??neuroelectrophysiology studies and muscle biopsy??provide important clues to detecting the virulence genes.     

Neuromuskuläre Erkrankungen (NME)

Traditionally, muscular dystrophies (MDs) are progressive, hereditary, and primarily degenerative myopathies. Nowadays, due to molecular biology, MDs are looked upon as clinically and genetically heterogeneous myopathies characterized by protein defects of muscle tissue resulting most often in muscle weakness. They are caused by gene mutations leading to a decrease of structural proteins or enzymes. The site of the primary defect and the protein function are different. The disorders are defined according to the underlying protein defect (dystrophinopathy, calpainopathy, and others). The gene or gene product are not yet known in all forms of MD (for example, facioscapulohumeral muscular dystrophy). Therefore, the nomenclature based on the protein defects and the term MD are used concurrently.Clinical symptoms, pathogenesis, diagnosis, therapy, prognosis, and possible prevention of the more frequent MDs are discussed: dystrophinopathies (Duchenne, Becker type), Emery-Dreifuss syndrome (3 forms), facioscapulohumeral MD, limb-girdle MD (17 forms), myotonic dystrophies (2 forms), and congenital MD (11 forms).This article highlights the significance of molecular analyses and the possible multisystemic symptoms in these myopathies.     

Myopathy and neurogenic muscular atrophy in unexpected cardiopulmonary arrest

Background: Neuromuscular disorders can be the cause of sudden death of infants because of their weakness and gastroesophageal reflux (GER). Methods: Muscle biopsy and genetic studies were performed by usual method. Results: In this report four cases of infants with neuromuscular disorders (two cases of congenital myopathy and two cases of spinal muscular atrophy) who had unexpected cardiopulmonary arrest on arrival (CPAOA) are presented. Two of the cases did not show any symptoms, such as muscle weakness prior to CPAOA. The diagnosis was based on the results of the muscle biopsy and genetic examination. Conclusion: These results suggest that sudden infant death caused by neuromuscular disorders should be considered.     

The hypotonic infant: case study of central core disease

Causes of hypotonia in the newborn can be broadly categorized into two classifications. Hypotonia with a supraspinal origin may be seen with systemic disease, hypoxic ischemic encephalopathy, cerebral malformations, syndromes (for example: Down, Prader-Willi, Lowe, Zellweger, Smith-Lemli-Opitz), and c-spine injury. Disorders of the motor unit that present with hypotonia in the newborn period include SMA, congenital myotonic dystrophy, congenital myasthenia gravis, and congenital myopathies. Central core disease is one of the classic congenital myopathies that can be differentiated based on characteristic histologic findings. Muscle fiber samples from patients with central core disease possess distinct morphology that can be diagnostic. Many infants may not exhibit muscle weakness in the newborn period, although there have been rare cases of profound hypotonia and respiratory failure. Clearly, muscle biopsy is the gold standard and is indicated for any infant with marked hypotonia that is not thought to be supraspinal in origin.     

Congenital muscular dystrophy with laminin-a2 deficiency in early infancy: diagnosis and long-term follow-up

Congenital muscular dystrophy (CMD) is a heterogeneous group of neuromuscular disorders characterized by muscle weakness and hypotonia at birth or within the first few months of life. It is inherited in an autosomal recessive pattern. About half of the patients have a deficiency of the alpha-2-chain of laminin (merosin). We describe a case of congenital muscular dystrophy in an infant with laminin-a2-chain deficiency, which appeared hypotonia in early infancy. Diagnosis was made by clinical features and the histological and immunohistochemical studies on muscle biopsy.     

Classification and diagnostic criteria of variants of Hirschsprung’s disease

“Variants of Hirschsprung’s disease” are conditions that clinically resemble Hirschsprung’s disease (HD), despite the presence of ganglion cells in rectal suction biopsies. The diagnosis and management of these patients can be challenging. Specific histological, immunohistochemical and electron microscopic investigations are required to characterize this heterogeneous group of functional bowel disorders. Variants of HD include intestinal neuronal dysplasia, intestinal ganglioneuromatosis, isolated hypoganglionosis, immature ganglia, absence of the argyrophil plexus, internal anal sphincter achalasia and congenital smooth muscle cell disorders such as megacystis microcolon intestinal hypoperistalsis syndrome. This review article systematically classifies variants of HD based on current diagnostic criteria with an additional focus on pathogenesis, epidemiology, clinical presentation, management and outcome.     

Intestinale Motilitätsstörungen

Intestinal motility disorders may result from a disturbed intrinsic or extrinsic innervation, a myopathy of the intestinal muscle layers, or a hormonal or immunological dysfunction. In the absence of an organic or biochemical abnormality a functional disorder is considered. The symptoms of intestinal motility disorders are unspecific and do not allow to predict the aetiology or the prognosis of the disease: distended abdomen, nausea, vomiting, abdominal pain, failure to thrive, constipation and chronic intestinal pseudoobstruction (CIPO). The classification of intestinal motility disorders is based on clinical and morphological criteria and includes familial and non-familial, primary and secondary myopathies and neuropathies. Several monogenetic disorders can be diagnosed by molecular genetic techniques (e. g. Hirschsprung's disease, Waardenburg-Shah Syndrome). With the exception of Hirschsprung's disease, therapeutic decisions are based on the clinical picture and not on histology.