Muscular dystrophies.

Muscular dystrophies are primary diseases of muscle due to mutations in more than 40 genes, which result in dystrophic changes on muscle biopsy. Now that most of the genes responsible for these conditions have been identified, it is possible to accurately diagnose them and implement subtype-specific anticipatory care, as complications such as cardiac and respiratory muscle involvement vary greatly. This development and advances in the field of supportive medicine have changed the standard of care, with an overall improvement in the clinical course, survival, and quality of life of affected individuals. The improved understanding of the pathogenesis of these diseases is being used for the development of novel therapies. In the most common form, Duchenne muscular dystrophy, a few personalised therapies have recently achieved conditional approval and many more are at advanced stages of clinical development. In this Seminar, we concentrate on clinical manifestations, molecular pathogenesis, diagnostic strategy, and therapeutic developments for this group of conditions.

[Congenital muscular dystrophies in children]. / Distrofias musculares congénitas en el niño.

From the clinical and genetic point of view, congenital muscular dystrophies (CMD) are a heterogenic group of diseases within neuromuscular pathologies. The best known forms are: merosin deficiency CMD, collagen VI deficiency CMD, LMNA-related CMD, selenoprotein-related CMD (SEPN1) and alpha-dystroglycan-related CMD. They present with a broad spectrum of clinical phenotypes. Most of them are transmitted by recessive autosomal inheritance. The initial manifestations very often begin in infancy or in the neonatal period. There are clinical suspicions of the existence of hypotonia and paresis, and they are characterised by a dystrophic pattern in the muscular biopsy (muscle replaced by fibroadipose tissue, with necrosis and cell regeneration). Advances in the understanding of the molecular pathogenesis of CMD have made it possible to make further progress in the classification of the different subtypes. The aim of this review is to comment on the advances made in recent years as regards the classification of CMD in terms of genetics, the proteins involved and their clinical presentation.

TITLE: Distrofias musculares congenitas en el niño.Las distrofias musculares congenitas (DMC) representan desde el punto de vista clinico y genetico un grupo heterogeneo de enfermedades dentro de la patologia neuromuscular. Las formas mas conocidas son: DMC por deficit de merosina, DMC por deficit de colageno VI, DMC relacionada con LMNA, DMC relacionada con selenoproteina (SEPN1) y las DMC vinculadas a los alfa-distroglicanos. Se presentan con un amplio espectro de fenotipos clinicos. En su mayoria son de herencia autosomica recesiva. Con mucha frecuencia las manifestaciones iniciales comienzan en la infancia o en el periodo neonatal. Se sospechan clinicamente por la existencia de hipotonia y paresia y se caracterizan por la existencia de un patron distrofico en la biopsia muscular (sustitucion de musculo por tejido fibroadiposo, con necrosis y regeneracion celular). Avances en la comprension de la patogenesis molecular de las DMC han permitido profundizar en la clasificacion de los diferentes subtipos. El objetivo de esta revision es comentar los avances de los ultimos años en cuanto a la clasificacion de las DMC en relacion a la genetica, las proteinas involucradas y su presentacion clinica.

Mouse models of fukutin-related protein mutations show a wide range of disease phenotypes.

Dystroglycanopathies are characterized by a reduction in the glycosylation of alpha-dystroglycan (α-DG). A common cause for this subset of muscular dystrophies is mutations in the gene of fukutin-related protein (FKRP). FKRP mutations have been associated with a wide spectrum of clinical severity from severe Walker-Warburg syndrome and muscle-eye-brain disease with brain and eye defects to mild limb-girdle muscular dystrophy 2I with myopathy only. To examine the affects of FKRP mutations on the severity of the disease, we have generated homozygous and compound heterozygous mouse models with human mutations in the murine FKRP gene. P448Lneo+ and E310delneo+ mutations result in severe dystrophic and embryonic lethal phenotypes, respectively. P448Lneo+/E310delneo+ compound heterozygotes exhibit brain defects and severe muscular dystrophies with near absence of α-DG glycosylation. Removal of the Neo(r) cassette from the P448Lneo+ homozygous mice eliminates overt brain and eye defects, and reduces severity of dystrophic phenotypes. Furthermore, introduction of the common L276I mutation to generate transgenic L276Ineo+ homozygous and L276Ineo+/P448Lneo+ and L276Ineo+/E310delneo+ compound heterozygotes results in mice displaying milder dystrophies with reduced α-DG glycosylation and no apparent brain defects. Limited sampling and variation in functionally glycosylated α-DG levels between and within muscles may explain the difficulties in correlating FKRP expression levels with phenotype in clinics. The nature of individual mutations, expression levels and status of muscle differentiation all contribute to the phenotypic manifestation. These mutant FKRP mice are useful models for the study of disease mechanism(s) and experimental therapies.

Myofibrillar myopathies.

Myofibrillar myopathies represent a group of muscular dystrophies with a similar morphologic phenotype. They are characterized by a distinct pathologic pattern of myofibrillar dissolution associated with disintegration of the Z-disk, accumulation of myofibrillar degradation products, and ectopic expression of multiple proteins and sometimes congophilic material. The clinical features of myofibrillar myopathies are more variable. These include progressive muscle weakness, that often involves or begins in distal muscles but limb-girdle or scapuloperoneal distributions can also occur. Cardiomyopathy and peripheral neuropathy are frequent associated features. EMG of the affected muscles reveals myopathic motor unit potentials and abnormal irritability often with myotonic discharges. Rarely, neurogenic motor unit potentials or slow nerve conductions are present. The generic diagnosis of myofibrillar myopathies is based on muscle biopsy findings in frozen sections. To date, all myofibrillar myopathy mutations have been traced to Z-disk-associated proteins, namely, desmin, αB-crystallin, myotilin, ZASP, filamin C and Bag3. However, in the majority of the myofibrillar myopathy patients the disease gene awaits discovery.

[Muscular dystrophies]. / Muskeldystrophien.

The diagnosis "muscular dystrophy" without analysis of the underlying gene defect is nowadays obsolete. With the discovery and cloning of cytoskeleton proteins and intermediate filaments in the muscle fiber membrane, the sarcoplasm and the nucleus which are essential for the normal muscle fiber function, the classification of muscular dystrophies has dramatically improved. Muscular dystrophies are a group of clinically and genetically heterogeneous disorders. By means of immunohistochemistry and molecular genetics more than 40 different disease forms can be distinguished, which are characterised by distinct protein defects or defined gene loci and can be related to typical phenotypes. It is noteworthy that muscular dystrophies may be associated with cardiomyopathy with increased risk of sudden cardiac death. Thus, diagnosis and treatment require experienced investigators and clinicians and regular cardiologic follow-ups, preferably in a specialised muscle center.

Differential diagnosis of congenital muscular dystrophies.

Congenital muscular dystrophies (CMDs) are defined by signs of muscle weakness in the first 6 months of life with myopathic changes in muscle biopsy. The progress in the last decade has helped to make molecular and genetic diagnoses in the majority of patients fulfilling these criteria. In a number of patients a definite diagnosis cannot be reached and these individuals are often grouped together as "merosin positive" congenital muscular dystrophy. In the last 5 years, 25 patients referred for assessment as possible congenital muscular dystrophy have been found to have alternative diagnoses. This paper aims to highlight these conditions as the common differentials or more difficult to diagnoses to consider in patients presenting as CMD.

Tumour necrosis factor-mediated cell death pathways do not contribute to muscle fibre death in dystrophinopathies.

There is evidence that apoptotic cell death mechanisms contribute to muscle fibre loss in dystrophinopathies, but little knowledge about the activators of the final degrading caspase cascade in muscle fibre apoptosis. As mitochondria-related activation of this caspase cascade, through e.g. APAF-1, could not be proven in dystrophin-deficient muscle, this study searches for other prospective candidates that may directly trigger apoptotic cell degradation by mitochondria-independent pathways involving the interaction of tumour necrosis factor-alpha (TNF-alpha) and TRAIL with death receptors and subsequent activation of caspase-8. The expression of TNF-alpha, TNF-R1, TRAIL, NF-(kappa)B and caspase-8 were studied in muscle biopsy specimens from 14 patients with a dystrophinopathy [10 Duchenne muscular dystrophies (DMD), 2 Becker MD, and 2 DMD carriers] by immunohistochemistry and Western blotting. In all types of dystrophinopathies, necrotic muscle fibres undergoing myophagocytosis displayed strong expression of TNF-alpha, TNF-R1, and TRAIL, which, however, was attributed to phagocytosing cells and not to the muscle fibres themselves. There was no up-regulation in normal-shaped or atrophic non-necrotic muscle fibres, or in intact muscle fibre segments adjacent to segmental necrosis and myophagocytosis. The expression profiles of caspase-8 and NF-(kappa)B resembled that of normal control muscle. There were likewise no significant differences in the Western blot analyses between normal control and dystrophin-deficient muscle. Based on these findings, a contribution of TNF-alpha or TRAIL-mediated cell death pathways to muscle fibre apoptosis or necrosis in dystrophinopathies could not be confirmed.

[Recent advances in congenital muscular dystrophy research].

Congenital muscular dystrophy (CMD) is a group of heterogeneous disorders characterized clinically by delayed milestones due to generalized muscle weakness and dystrophic muscle pathology. The discovery of fukutin, responsible gene for Fukuyama CMD (FCMD) and defective glycosylation in its muscle biopsy has lead significant advances in CMD researches, especially disorders with glycosylation defects to a dystroglycan (alphaDG). The highly glycosylated a DG is one of the major dystrophin-associated proteins anchored a basement membrane protein, laminin 2 to the dystrophin molecule. The disorders with the defective glycosylation are now categorized as a dystroglycanopathies which include FCMD, muscle-eye-brain (MEB) disease, Walker-Warburg syndrome (WWS) and diseases with mutations in fukutin-related protein (FKRP) and LARGE genes. Among them, MEB and WWS were proven to have mutations in the glycosyltransferase genes, POMGnT1 (protein O-mannose beta 1,2-N-acetylglucosaminyl/transferase 1) and POMT1 (protein O-mannosyltransferase 1), respectively, though others are still unknown how the glycosylation defect is induced. Although the disease with FKRP mutation has variable phenotypes from CMD to limb-girdle muscular dystrophy, others with defective to decreased a DG show CMD, central nervous system involvement with migration disorder (polymicrogyria) and ocular abnormalities.

[Two sisters with dysferlinopathy manifesting different clinical phenotypes].

We report two sisters with dysferlinopathy who manifested different clinical phenotypes. A 22-year-old female (patient 1) noticed of difficulty in running at the age of 13 years, and since then weakness of the lower extremities has progressed slowly. She had typical features of Miyoshi myopathy (MM); i.e., young adult onset, dominant involvement of calf muscles and markedly elevated serum creatine kinase (CK). Her 19-year-old sister (patient 2) first noticed of weakness in lower extremities at age 12 years. On neurological examination, she had proximally dominant muscle weakness, consistent with limb girdle muscular dystrophy type 2B (LGMD2B); serum CK level was also markedly elevated. On MRI study of muscle, patient 1 showed fatty degeneration of calf muscles, whereas patient 2 showed no abnormality in quadriceps and calf muscles. Immunohistochemistry of the muscle biopsy specimens using anti-dysferlin antibody showed deficiency of this protein in sarcolemma. There have been only a few reports of sibling cases of dysferlinopathy whose clinical phenotypes are different. These sibling cases may have important suggestion on the mechanism(s) of phenotypic variation of dysferlinopathy.

Clinical, morphological and immunological evaluation of six patients with dysferlin deficiency.

Limb girdle muscular dystrophy (LGMD) type 2B and distal Miyoshi myopathy (MM) are caused by mutations in a recently discovered mammalian gene coding for a skeletal muscle protein called dysferlin. The protein is normally expressed at the skeletal muscle level and absent or reduced in affected patients. We selected a clinically heterogeneous population of Italian myopathic patients with clinical evidence of myopathy and/or hyperCKemia, EMG myopathic pattern, and no alterations of the dystrophin-sarcoglycan complex. Calpain, merosin, emerin and caveolin were also tested and found normal in all patients. Dysferlin immunohistochemical and Western blot analyses allowed us to identify six patients with dysferlin deficiency: one with distal myopathy, four with limb girdle myopathy and one with hyperCKemia. No apoptosis was found in any of the six muscle specimens, although expression of the pro-apoptotic Fas antigen was mildly increased in two cases. Inflammatory reactions were present in two of the six cases, but we found no evidence of immune-mediated processes.

Protein and gene analyses of dysferlinopathy in a large group of Japanese muscular dystrophy patients.

Mutations in the dysferlin gene cause muscular dystrophies called dysferlinopathy, which include limb-girdle muscular dystrophy type 2B (LGMD2B) and Miyoshi myopathy (MM). To clarify the frequency, clinicopathological and genetic features of dysferlinopathy in Japan, we performed protein and gene analyses of dysferlin. We examined a total of 107 unrelated Japanese patients, including 53 unclassified LGMD, 28 MM and 26 other neuromuscular disorders (ONMD). Expression of dysferlin protein was observed using immunohistochemistry (IHC) and mini-multiplex Western blotting (MMW), and mutation analysis was performed. We found a deficiency of dysferlin protein by both IHC and MMW in 19% of LGMD and 75% of MM patients, and mutations in the dysferlin gene were identified in this group alone. 19% of dysferlin-deficient patients had 3370G-->T missense mutation and 16% had 1939C-->G nonsense mutation. The patients with homozygous 3370G-->T mutation showed milder clinical phenotypes. Twenty-five percent of MM muscles had normal dysferlin protein contents that suggested the genetic heterogeneity of this disease. Altered immunolocalization of dysferlin was observed in not only primary dysferlinopathy, but also in the several diseased muscles with normal protein contents. This result implies the necessity of other protein(s) for proper membrane localization of dysferlin, or some roles of dysferlin in the cytoplasmic region.

The phenotype of limb-girdle muscular dystrophy type 2I.

BACKGROUND: Mutations in the fukutin-related protein gene FKRP cause limb-girdle muscular dystrophy (LGMD2I) as well as a form of congenital muscular dystrophy (MDC1C). OBJECTIVE: To define the phenotype in LGMD2I. METHODS: The authors assessed 16 patients from 14 families with FKRP gene mutations and LGMD and collected the results of mutation analysis, protein studies, and respiratory and cardiac investigations. RESULTS: Thirteen patients, most with adult presentation, were homozygous for the common C826A mutation in FKRP. The three other cases were compound heterozygotes for C826A and two of them presented in childhood, with more progressive disease. The pattern of muscle involvement, frequently including calf hypertrophy, was similar to dystrophinopathy. Complications in patients with LGMD2I were common and sometimes out of proportion to the skeletal muscle involvement. Six patients had cardiac involvement, and 10 had respiratory impairment: five required nocturnal respiratory support. All patients had serum creatine kinase at least 5 to 70 times normal. The most consistent protein abnormality found on muscle biopsy was a reduction of laminin alpha2 immunolabeling, either on muscle sections or immunoblotting alone. CONCLUSIONS: LGMD2I due to FKRP mutations appears to be a relatively common cause of LGMD, with respiratory and cardiac failure as prominent complications.

Walker-warburg syndrome: reports of two cases

The purpose of this study is to describe two infants that were diagnosed with Walker-Warburg syndrome (WWS), a rare form of congenital muscular dystrophy (CMD). They were studied in their clinical, laboratory, and neuroradiologic features. The index case had a brain magnetic resonance imaging (MRI) and the second patient had a head computerized tomography (CT). In addition, a literature review was performed to describe the main forms of CMD. The index case fulfilled all criteria for WWS. A brain MRI performed at age 4 months served to corroborate the clinical diagnosis, showing severe hydrocephalus, type II lissencephaly, cerebellar vermian aplasia, and a hypoplastic brain stem. The authors were able to establish a retrospective diagnosis of WWS in the index cases's older sister, based upon her clinical picture and head CT report.

Comparative analysis between Duchenne and Becker types muscular dystrophy.

Duchenne and Becker types of muscular dystrophy are usually differentiated according to age of onset and rate of progression criteria which are not sufficient. The aim of this paper was to re-establish the clues for distinguishing Duchenne from Becker types of muscular dystrophy. According to the onset and progression of the disease, one hundred and eleven patients were subdivided into two groups. First group--Becker muscular dystrophy--consisted of 40 patients and second one of 71 patients with Duchenne type of muscular dystrophy. Clinical data confirm some well known differences between Duchenne and Becker muscular dystrophy concerning the age of onset, severity of disease and rate of progression. Electromyographic signs of myopathic changes and spontaneous activity were found in both diseases. Spontaneous activity--bizarre and fibrillation potentials, as well as sharp waves are more common for Duchenne type. The differences between the Becker from Duchenne type of muscular dystrophy can be described on the basis of complex investigations (clinical, electromyographical, histological and biochemical).

[Tibial muscular dystrophy. A rare form of distal myopathy]. / La myopathie tibiale. Une forme rare de myopathie distale.

Tibial muscular dystrophy (TMD) is a dominantly inherited late onset distal leg myopathy only described in the Finnish population as yet. A similar disorder was described by Markesbery et al. in 1974 in one American family. Assignment of the TMD locus to chromosome 2q31 has been demonstrated (Haravuori et al., 1998). We recently described a French family with clinical and laboratory findings similar to TMD (de Seze et al., 1998). Molecular genetic results indicate that the distal myopathy in this family could be linked to the TMD locus confirming TMD exists outside the Finish population. This overview of TMD will allow to describe differential diagnoses such as other distal myopathies and scapuloperoneal syndromes.

[Distal Miyoshi muscular dystrophy in a Moroccan patient]. / Myopathie distale de Miyoshi chez un Marocain.

BACKGROUND: Muscular dystrophy usually involves a deficiency in the proximal muscles. We report a case of distal muscular dystrophy in a Moroccan patient. CASE REPORT: A 21-year-old Moroccan complained of progressive onset weakness of the lower limbs and frequent falls. The neurological examination demonstrated amyotrophy involving both legs and almost complete regression of the posterior muscle compartment. Clinical findings were confirmed by muscle scans. The electromyogram showed a progressive myogenic process. Creatine kinase was elevated. The severe dystrophic aspect was evidenced at muscle biopsy and led to the diagnosis of distal Miyoshi muscular dystrophy. DISCUSSION: Miyoshi muscular dystrophy, a distal myopathy transmitted by autosomal recessive inheritance, is usually observed in young adults who present characteristic amyotrophy of the posterior leg muscles. The proximal muscles of the lower and upper limbs may become involved during the disease course. Approximately one-third of the patients require wheel chair assistance after 10 years. Creatine kinase levels are constantly elevated. The differential diagnosis with other muscular dystrophies predominating in the distal muscles, particularly Steinert's myotonic dystrophy and inclusion body myositis, is discussed.

[Current diagnosis in muscular dystrophies. New developments, methods of examination and case examples]. / Aktuelle Diagnostik bei Muskeldystrophien. Neue Entwicklungen, Untersuchungsmethoden und Fallbeispiele.

Recent progress in the field of molecular genetics revealed a broader spectrum of dystrophin-related disorders than previously assumed. In addition, the pathogenetic basis of other types of muscular dystrophies could be identified: some autosomal-recessive limb girdle dystrophies are caused by mutations of sarcoglycan genes, others are caused by deficiency of the sarcoplasmatic enzyme calpain-3. Emery-Dreifuss muscular dystrophy is due to the deficiency of the nuclear membrane protein emerin. About 50% of congenital muscular dystrophies are related to mutations of a extracellular matrix protein merosin (alpha-laminin). A series of monoclonal antibodies for immunohistochemistry is now available recognizing many cytoskeletal muscle proteins. In combination with molecular genetics a diagnostic flow chart can be developed which allows a definite diagnosis in most cases. In this review disease entities are illustrated by case reports. We discuss the significance of immunohistochemical and molecular methods for diagnosis.

Neuroimaging manifestations and classification of congenital muscular dystrophies.

BACKGROUND AND PURPOSE: Recent work has shown that up to 50% of patients with congenital muscular dystrophies (CMDs) have abnormalities of the brain that can be detected by brain MR imaging. We attempted to determine whether brain MR imaging is useful for the diagnosis and classification of patients with CMDs. METHODS: The brain MR studies of 12 patients with biopsy-proved CMDs were reviewed retrospectively. Using information available in the literature regarding associated brain anomalies as a guide, an attempt was made to classify the patients in terms of "pure" CMD, CMD with occipital agyria, Fukuyama CMD, muscle-eye-brain disease, or Walker-Warburg syndrome. RESULTS: All the patients were easily classified into one of four groups: pure CMD (four patients), Fukuyama CMD (four patients), muscle-eye-brain disease (two patients), or Walker-Warburg syndrome (two patients). Patients with pure CMD had diffuse central cerebral hypomyelination with mild pontine and cerebellar hypoplasia. Patients with Fukuyama CMD had diffuse central cerebral hypomyelination, cerebellar polymicrogyria (with or without cysts), frontal polymicrogyria, a variable degree of hypoplasia of the pons and cerebellar vermis, and a variable occipital cobblestone cortex. Patients with muscle-eye-brain disease had cerebellar polymicrogyria (with or without cysts), absence of the septum pellucidum, diffuse cerebral cortical dysplasia, pontine and cerebellar vermian hypoplasia, patchy hypomyelination, and variable callosal hypogenesis and hydrocephalus. Patients with Walker-Warburg syndrome had diffuse cerebral cobblestone cortex, absence of cerebral and cerebellar myelin, cerebellar polymicrogyria (with or without cysts), pontine and cerebellar vermal hypoplasia, hydrocephalus, and variable callosal hypogenesis. CONCLUSION: MR imaging shows distinctive brain anomalies that allows patients with CMD to be classified into four distinct groups that are consistent with known disorders.