Diagnoses of muscular dystrophy in a veterans health system.

INTRODUCTION/AIMS: Early diagnosis of a chronic neuromuscular disease such as muscular dystrophy (MD) generally excludes an individual from active-duty military service. However, it is not known whether veterans are sometimes diagnosed with milder forms of MD at a later timepoint. We aimed to determine the prevalence of MD in a veterans health system. METHODS: We abstracted clinical and genetic test data on patients who received care for a diagnosis of MD at the North Florida/South Georgia Veterans Health System between 2008 and 2021. We then determined which of these individuals would meet criteria for a definite diagnosis of MD, based on electrodiagnostic testing, muscle biopsy, and genetic testing of the individual or an affected first degree relative. RESULTS: We identified 12 patients with definite MD and 36 with possible or probable MD. The definite cases included myotonic dystrophy type 1 (4), myotonic dystrophy type 2 (3), oculopharyngeal MD (2), Becker MD (1), distal MD (1), and facioscapulohumeral MD (1). At least five of the cases classified as definite developed symptoms after discharge from active duty. DISCUSSION: Clinicians who care for veterans should be knowledgeable about, and have access to, diagnostic testing and treatment options for MD. When conducting MD surveillance, it is important to include veterans health systems as a data source. Mild cases of MD and those of later onset appear to be compatible in some cases with successful completion of military service.

Global prevalence of Duchenne and Becker muscular dystrophy: a systematic review and meta-analysis.

BACKGROUND: A variety of mutations in the largest human gene, dystrophin, cause a spectrum from mild to severe dystrophin-associated muscular dystrophies. Duchenne (DMD) and Becker (BMD) muscular dystrophies are located at the severe end of the spectrum that primarily affects skeletal muscle. Progressive muscle weakness in these purely genetic disorders encourages families with a positive history for genetic counseling to prevent a recurrence, which requires an accurate prevalence of the disorder. Here, we provide a systematic review and meta-analysis to determine the prevalence of DMD and BMD worldwide. METHOD: The current systematic review and meta-analysis was carried out using Cochrane seven-step procedure. After determining the research question and inclusion and exclusion criteria, the MagIran, SID, ScienceDirect, WoS, ProQuest, Medline (PubMed), Embase, Cochrane, Scopus, and Google Scholar databases were searched to find relevant studies using defined keywords and all possible keyword combinations using the AND and OR, with no time limit until 2021. The heterogeneity of studies was calculated using the I2 test, and the publication bias was investigated using the Begg and Mazumdar rank correlation test. Statistical analysis of data was performed using Comprehensive Meta-Analysis software (version 2). RESULTS: A total of 25 articles involving 901,598,055 people were included. The global prevalence of muscular dystrophy was estimated at 3.6 per 100,000 people (95 CI 2.8-4.5 per 100,000 people), the largest prevalence in the Americans at 5.1 per 100,000 people (95 CI 3.4-7.8 per 100,000 people). According to the subgroup analysis, the prevalence of DMD and BMD was estimated at 4.8 per 100,000 people (95 CI 3.6-6.3 per 100,000 people) and 1.6 per 100,000 people (95 CI 1.1-2.4 per 100,000 people), respectively. CONCLUSION: Knowing the precise prevalence of a genetic disorder helps to more accurately predict the likelihood of preventing its occurrence in families. The global prevalence of DMD and BMD was very high, indicating the urgent need for more attention to prenatal screening and genetic counseling for families with a positive history.

Prevalence and incidence of neuromuscular conditions in the UK between 2000 and 2019: A retrospective study using primary care data.

BACKGROUND: In the UK, large-scale electronic primary care datasets can provide up-to-date, accurate epidemiological information on rarer diseases, where specialist diagnoses from hospital discharges and clinic letters are generally well recorded and electronically searchable. Current estimates of the number of people living with neuromuscular disease (NMD) have largely been based on secondary care data sources and lacked direct denominators. OBJECTIVE: To estimate trends in the recording of neuromuscular disease in UK primary care between 2000-2019. METHODS: The Clinical Practice Research Datalink (CPRD) database was searched electronically to estimate incidence and prevalence rates (per 100,000) for a range of NMDs in each year. To compare trends over time, rates were age standardised to the most recent CPRD population (2019). RESULTS: Approximately 13 million patients were actively registered in each year. By 2019, 28,230 active patients had ever received a NMD diagnosis (223.6), which was higher among males (239.0) than females (208.3). The most common classifications were Guillain-Barre syndrome (40.1), myasthenia gravis (33.7), muscular dystrophy (29.5), Charcot-Marie-Tooth (29.5) and inflammatory myopathies (25.0). Since 2000, overall prevalence grew by 63%, with the largest increases seen at older ages (≥65-years). However, overall incidence remained constant, though myasthenia gravis incidence has risen steadily since 2008, while new cases of muscular dystrophy fell over the same period. CONCLUSIONS: Lifetime recording of many NMDs on primary care records exceed current estimates of people living with these conditions; these are important data for health service and care planning. Temporal trends suggest this number is steadily increasing, and while this may partially be due to better recording, it cannot be simply explained by new cases, as incidence remained constant. The increase in prevalence among older ages suggests increases in life expectancy among those living with NMDs may have occurred.

Functional performance and muscular strength in symptomatic female carriers of Duchenne muscular dystrophy / Desempenho funcional e força muscular em portadoras sintomáticas de distrofia muscular de Duchenne

Abstract Duchenne muscular dystrophy (DMD) usually affects men. However, women are also affected in rare instances. Approximately 8% of female DMD carriers have muscle weakness and cardiomyopathy. The early identification of functional and motor impairments can support clinical decision making. Objective: To investigate the motor and functional impairments of 10 female patients with dystrophinopathy diagnosed with clinical, pathological, genetic and immunohistochemical studies. Methods: A descriptive study of a sample of symptomatic female carriers of DMD mutations. The studied variables were muscular strength and functional performance. Results: The prevalence was 10/118 (8.4%) symptomatic female carriers. Deletions were found in seven patients. The age of onset of symptoms in female carriers of DMD was quite variable. Pseudohypertrophy of calf muscles, muscular weakness, compensatory movements and longer timed performance on functional tasks were observed in most of the cases. Differently from males with DMD, seven female patients showed asymmetrical muscular weakness. The asymmetric presentation of muscle weakness was frequent and affected posture and functionality in some cases. The functional performance presents greater number of compensatory movements. Time of execution of activities was not a good biomarker of functionality for this population, because it does not change in the same proportion as the number of movement compensations. Conclusion: Clinical manifestation of asymmetrical muscle weakness and compensatory movements, or both can be found in female carriers of DMD mutations, which can adversely affect posture and functional performance of these patients.

Resumo A distrofia muscular de Duchenne (DMD) geralmente afeta indivíduos do sexo masculino. No entanto, mulheres também são acometidas em casos raros. Aproximadamente 8% das portadoras de DMD têm fraqueza muscular ou cardiomiopatia. A identificação precoce das alterações funcionais e motoras pode alterar a tomada de decisão clínica. Objetivo: Investigar as deficiências motoras e funcionais de 10 pacientes do sexo feminino com distrofinopatia diagnosticada por estudos clínicos, patológicos, genéticos e imuno-histoquímicos. Método: Estudo descritivo de uma amostra de portadoras sintomáticas de mutações DMD. As variáveis estudadas foram força muscular e desempenho funcional. Resultados: A prevalência foi de 10/118 (8,4%) de portadoras sintomáticas de DMD. Foram encontradas deleções em sete pacientes. A idade de início dos sintomas em portadoras de DMD foi variável. Pseudo-hipertrofia de panturrilhas, movimentos compensatórios, fraqueza muscular e aumento no tempo de execução de tarefas funcionais foram observados na maioria dos casos. Diferentemente dos homens com DMD, sete pacientes apresentaram fraqueza muscular assimétrica. A apresentação assimétrica da fraqueza muscular foi frequente, podendo afetar a postura e a funcionalidade. O desempenho funcional geralmente apresenta aumento no número de movimentos compensatórios. Não podemos sempre considerar o tempo como um bom marcador de funcionalidade para essa população, uma vez que não muda na mesma proporção que o número de compensações em todas essas pacientes. Conclusão: Fraqueza muscular assimétrica e movimentos compensatórios, ou ambos, podem ser encontrados em portadoras sintomáticas de DMD, o que pode afetar a postura e a funcionalidade dessas pacientes.

Cardiac and Neuromuscular Features of Patients With LMNA-Related Cardiomyopathy.

Background: Mutations in the LMNA (lamin A/C) gene have been associated with neuromuscular and cardiac manifestations, but the clinical implications of these signs are not well understood. Objective: To learn more about the natural history of LMNA-related disease. Design: Observational study. Setting: 13 clinical centers in Italy from 2000 through 2018. Patients: 164 carriers of an LMNA mutation. Measurements: Detailed cardiologic and neurologic evaluation at study enrollment and for a median of 10 years of follow-up. Results: The median age at enrollment was 38 years, and 51% of participants were female. Neuromuscular manifestations preceded cardiac signs by a median of 11 years, but by the end of follow-up, 90% of the patients had electrical heart disease followed by structural heart disease. Overall, 10 patients (6%) died, 14 (9%) received a heart transplant, and 32 (20%) had malignant ventricular arrhythmias. Fifteen patients had gait loss, and 6 had respiratory failure. Atrial fibrillation and second- and third-degree atrioventricular block were observed, respectively, in 56% and 51% of patients with combined cardiac and neuromuscular manifestations and 37% and 33% of those with heart disease only. Limitations: Some of the data were collected retrospectively. Neuromuscular manifestations were more frequent in this analysis than in previous studies. Conclusion: Many patients with an LMNA mutation have neurologic symptoms by their 30s and develop progressive cardiac manifestations during the next decade. A substantial proportion of these patients will have life-threatening neurologic or cardiologic conditions. Primary Funding Source: None.

Congenital myopathies: clinical phenotypes and new diagnostic tools.

Congenital myopathies are a group of genetic muscle disorders characterized clinically by hypotonia and weakness, usually from birth, and a static or slowly progressive clinical course. Historically, congenital myopathies have been classified on the basis of major morphological features seen on muscle biopsy. However, different genes have now been identified as associated with the various phenotypic and histological expressions of these disorders, and in recent years, because of their unexpectedly wide genetic and clinical heterogeneity, next-generation sequencing has increasingly been used for their diagnosis. We reviewed clinical and genetic forms of congenital myopathy and defined possible strategies to improve cost-effectiveness in histological and imaging diagnosis.

Distrofia muscular de Duchenne: incidencia, prevalencia, características sociodemográficas y clínicas de pacientes ingresados a Teletón Chile desde 1993 a 2013 / Duchenne muscular dystrophy: incidence, prevalence, sociodemographic and clinical characteristics of patients admitted to Teletón Chile from 1993 to 2013

Duchenne muscular dystrophy (DMD) in their natural evolution leads to loss of ambulation between 7 and 13 years of age and death in adolescence close to 20 years. The estimated global incidence is of 1/3,500 male births; data in Chile is unknown. Objective: To estimate the incidence, prevalence of DMD and to describe clinical and sociodemographic characteristics of patients admitted to Teletón-Chile between 1993 and 2013. Patients and Method: A descriptive, retrospective, longitudinal study with review of medical records and database at Teletón. 462 DMD patients were admitted during the study period. Results: The incidence and prevalence in Teletón was of 1/6,558 male live births and the prevalence of 11.51 [CI 10.46 to 12.56] 105 men < 30 years. The average age of first consultation was 6.7 +/- 3.4 years, with mild or moderate functional level (65.6 percent). At the end of the study 67 percent were wheelchair users, with medical prescription at 10.8 +/- 3.3 years. 52.2 percent of patients were classified as extreme poverty, attended at Teletón centers of the central region (55.2 percent), and current average age of 14.7 +/- 5.7 years. 35.9 percent of DMD patients were dead at an average age of 18.1 +/- 3.5 years. Conclusion: The incidence and prevalence rates of DMD live births for males < 30 years admitted to Teletón, have declined between 1993-2011; as well as the average age of first consultation. The loss of ambulation and the average age of death are comparable with the current literature...

La distrofia muscular de Duchenne (DMD) en su evolución natural, produce pérdida de deambulación entre los 7 y 13 años de edad y la muerte en la adolescencia cercana a los 20 años. La incidencia mundial se estima de 1/3.500 nacimientos masculinos; en Chile se desconoce su magnitud. Objetivo: Estimar tasas de incidencia, prevalencia de DMD y describir características clínicas y sociodemográficas de pacientes ingresados a Institutos Teletón-Chile (IT) entre 1993 y 2013. Pacientes y Método: Estudio descriptivo, retrospectivo, longitudinal, con revisión de fichas clínicas y base de datos de IT. Se identificaron 462 pacientes con DMD, ingresados en el período estudiado. Resultados: La tasa de incidencia en IT fue de 1/6.558 nacidos vivos masculinos y prevalencia de 11,51 [IC: 10,46-12,56] por 105 varones < 30 años. Edad media de primera consulta: 6,7 +/- 3,4 años, con compromiso funcional leve o moderado (65,6 por ciento); al término del estudio el 67 por ciento eran usuarios de silla de ruedas, con prescripción médica a los 10,8 +/- 3,3 años. 52,2 por ciento de los pacientes de extrema pobreza, atendidos en IT zona central del país (55,2 por ciento), edad promedio actual de 14,7 +/- 5,7 años. El 35,9 por ciento estaban fallecidos, a la edad promedio de 18,1 +/- 3,5 años. Conclusión: Las tasas de incidencia y prevalencia de DMD para los nacidos vivos varones < 30 años ingresados a los IT, han disminuido entre 1993-2011; también la edad promedio de primera consulta. La pérdida de la marcha y la edad media de la defunción, son comparables con la literatura...

Anoctamin 5 muscular dystrophy in Denmark: prevalence, genotypes, phenotypes, cardiac findings, and muscle protein expression.

Since the initial description in 2010 of anoctamin 5 deficiency as a cause of muscular dystrophy, a handful of papers have described this disease in cases of mixed populations. We report the first large regional study and present data on new aspects of prevalence, muscular and cardiac phenotypic characteristics, and muscle protein expression. All patients in our neuromuscular unit with genetically unclassified, recessive limb girdle muscular dystrophy (LGMD2), Miyoshi-type distal myopathy (MMD) or persistent asymptomatic hyperCK-emia (PACK) were assessed for mutations in the ANO5 gene. Genetically confirmed patients were evaluated with muscular and cardiopulmonary examination. Among 40 unclassified patients (28 LGMD2, 5 MMD, 7 PACK), 20 were homozygous or compound heterozygous for ANO5 mutations, (13 LGMD2, 5 MMD, 2 PACK). Prevalence of ANO5 deficiency in Denmark was estimated at 1:100.000 and ANO5 mutations caused 11 % of our total cohort of LGMD2 cases making it the second most common LGMD2 etiology in Denmark. Eight patients complained of dysphagia and 3 dated symptoms of onset in childhood. Cardiac examinations revealed increased frequency of premature ventricular contractions. Four novel putative pathogenic mutations were discovered. Total prevalence and distribution of phenotypes of ANO5 disease in a representative regional cohort are described for the first time. A high prevalence of ANO5 deficiency was found among patients with unclassified LGMD2 (46 %) and MMD (100 %). The high incidence of reported dysphagia is a new phenotypic feature not previously reported, and cardiac investigations revealed that ANO5-patients may have an increased risk of ventricular arrhythmia.

Rapidly progressive scoliosis and respiratory deterioration in Ullrich congenital muscular dystrophy.

OBJECTIVE: To characterise the natural history of Ullrich congenital muscular dystrophy (UCMD). PATIENTS AND METHODS: Questionnaire-based nationwide survey to all 5442 certified paediatric and adult neurologists in Japan was conducted from October 2010 to February 2011. We enrolled the 33 patients (age at assessment, 11 ± 6.6 years) who were reported to have collagen VI deficiency on immunohistochemistry in muscle biopsies. We analysed the development, clinical manifestations, Cobb angle and %vital capacity (%VC) in spirogram. RESULTS: Cobb angle over 30° was noted at age 9.9 ± 5.3 years (n=17). The maximum progression rate was 16.2 ± 10°/year (n=13). %VC was decreased exponentially with age, resulting in severe respiratory dysfunction before pubescence. Scoliosis surgery was performed in 3 patients at ages 5 years, 9 years and 10 years. Postoperative %VC was relatively well maintained in the youngest patient. Non-invasive ventilation was initiated at age 11.2 ± 3.6 years (n=13). Twenty-five (81%) of 31 patients walked independently by age 1.7 ± 0.5 years but lost this ability by age 8.8 ± 2.9 years (n=11). Six patients never walked independently. CONCLUSIONS: The natural history of scoliosis, respiratory function and walking ability in UCMD patients were characterised. Although the age of onset varied, scoliosis, as well as restrictive respiratory dysfunction, progressed rapidly within years, once they appeared.

Congenital muscular dystrophies.

The congenital muscular dystrophies are a heterogeneous group of disorders in which weakness and dystrophic pattern on muscle biopsy are present at birth or during the first months of life. This chapter reviews the most common forms of congenital muscular dystrophies, including laminin α-2 (merosin) deficiency, Ullrich congenital muscular dystrophy, fukutin-related proteinopathy, rigid spine syndrome, and glycosylation disorders of α-dystroglycan. The latter group is often associated with neuronal migration defects including lissencephaly, pachygyria, cerebellar and brainstem abnormalities, and variable ocular anomalies. Typical clinical findings and underlying genetic defects are discussed to assist in the differential diagnosis and diagnostic work-up of patients with congenital muscular dystrophies. There are still no curative treatment options for patients with congenital muscular dystrophies but regular follow-up and symptomatic care by a multidisciplinary team considering the peculiarities of each disorder are important to maintain or improve patients' quality of life.

Congenital muscular dystrophies with cognitive impairment. A population study.

BACKGROUND: Cognitive impairment has been reported in a significant proportion of patients with congenital muscular dystrophies (CMD), generally associated with brain changes. OBJECTIVES: The aim of this study was to establish 1) the overall prevalence of CMD and cognitive impairment in the Italian population; 2) the frequency of individual genetically defined forms; and 3) the presence of distinct phenotypes not associated with mutations in the known genes. METHODS: We included all patients with CMD and cognitive impairment followed in all the Italian tertiary neuromuscular centers. Clinical, brain MRI, and morphologic data were collected. Genetic screening of the known genes was performed according to clinical and muscle biopsy findings. RESULTS: Ninety-two of the 160 (58%) patients with CMD followed in our centers had cognitive impairment. alpha-Dystroglycan (alpha-DG) reduction on muscle biopsy was found in 73/92 (79%), with 42/73 carrying mutations in the known genes. Another 6/92 (7%) showed a laminin alpha2 deficiency on muscle biopsy and 5 of the 6 carried mutations in LAMA2. The remaining 13/92 (14%) patients had normal alpha-DG and laminin alpha2 expression on muscle. CONCLUSIONS: This is the first population study establishing the prevalence of CMD and cognitive impairment and providing a classification on the basis of clinical, MRI, and genetic findings. We also showed that cognitive impairment was not always associated with alpha-DG or laminin alpha2 reduction or with structural brain changes.

Spectrum of mutations in sarcoglycan genes in the Mumbai region of western India: high prevalence of 525del T.

BACKGROUND: While the clinical and immunocytochemical features of sarcoglycanopathies have been reported from India, genetic aspects have not been studied. There is large variation in the sarcoglycan mutations among the studied populations. AIM: To study the spectrum of mutations in sarcoglycan genes (SG). MATERIALS AND METHODS: Patients fulfilling Bushby's criteria for limb girdle muscular dystrophy were prospectively analyzed. Patients gave their medical history and underwent a clinical examination, serum creatine kinase estimation, electrophysiology, muscle biopsy with immunostaining for alpha, beta, gamma, and delta subunits and mutational analysis using denaturing high pressure liquid chromatography and direct sequencing. RESULTS: Mutations in SG accounted for 26.4% of the cohort of limb girdle muscular dystrophy. The mean age of these 18 patients was 22.5 years. Generally, proximal weakness affected the flexor and adductor compartments of the lower and upper limbs. The clinical profile of various mutations was indistinguishable from each other. Gamma SG mutations were most common, seen in 8 patients, followed by delta SG mutation in 5 patients and alpha mutation in 4 patients, while only 1 patient had mutation in the beta sarcoglycan gene. The most prevalent mutation in the gamma SG gene was 525del T. This is of interest as the mutation has been known to exist only in specific populations. CONCLUSION: This study, the first mutational analysis of Indian patients with sarcoglycanopathies suggests gamma SG mutations were the most common and the most prevalent mutation in the gamma SG gene was 525del T.

Merosin-deficient congenital muscular dystrophy in Korea.

Congenital muscular dystrophy (CMD) is a clinically and genetically heterogeneous group of muscle disorders, presenting at birth or early infancy with hypotonia, muscle weakness, joint contractures, and dystrophic changes in the muscles. Merosin-deficient CMD (MDCMD) is rare in Asian populations, but more common in Caucasians, comprising about 50% of CMDs. We report, for the first time in Korea, eight patients with merosin-deficient CMD, confirmed by immunohistochemical staining of muscle or skin samples. We also describe their wide spectrum of clinical features and neuroimaging findings. Among 35 patients diagnosed as CMD, almost 23% of them were proved to have MDCMD with typical phenotypic presentation. We infer that prevalence of MDCMD in Korea may not be as low as expected. One of the patients was diagnosed by skin biopsy, which is good alternative for diagnosis of MDCMD.

A phase I/IItrial of MYO-029 in adult subjects with muscular dystrophy.

OBJECTIVE: Myostatin is an endogenous negative regulator of muscle growth and a novel target for muscle diseases. We conducted a safety trial of a neutralizing antibody to myostatin, MYO-029, in adult muscular dystrophies (Becker muscular dystrophy, facioscapulohumeral dystrophy, and limb-girdle muscular dystrophy). METHODS: This double-blind, placebo-controlled, multinational, randomized study included 116 subjects divided into sequential dose-escalation cohorts, each receiving MYO-029 or placebo (Cohort 1 at 1 mg/kg; Cohort 2 at 3 mg/kg; Cohort 3 at 10 mg/kg; Cohort 4 at 30 mg/kg). Safety and adverse events were assessed by reported signs and symptoms, as well as by physical examinations, laboratory results, echocardiograms, electrocardiograms, and in subjects with facioscapulohumeral dystrophy, funduscopic and audiometry examinations. Biological activity of MYO-029 was assessed through manual muscle testing, quantitative muscle testing, timed function tests, subject-reported outcomes, magnetic resonance imaging studies, dual-energy radiographic absorptiometry studies, and muscle biopsy. RESULTS: MYO-029 had good safety and tolerability with the exception of cutaneous hypersensitivity at the 10 and 30 mg/kg doses. There were no improvements noted in exploratory end points of muscle strength or function, but the study was not powered to look for efficacy. Importantly, bioactivity of MYO-029 was supported by a trend in a limited number of subjects toward increased muscle size using dual-energy radiographic absorptiometry and muscle histology. INTERPRETATION: This trial supports the hypothesis that systemic administration of myostatin inhibitors provides an adequate safety margin for clinical studies. Further evaluation of more potent myostatin inhibitors for stimulating muscle growth in muscular dystrophy should be considered.

[MD-NET--muscular dystrophy network]. / Das Muskeldystrophie-Netzwerk MD-NET.

Muscular dystrophies (MD) constitute a group of inherited disorders characterized by progressive weakness of skeletal and sometimes cardiac muscle. MD are rare disorders affecting approximately 26,000 to 40,000 people in Germany based on a pre valence of 1:2000 to 1:3000 (estimate of the Association Française contre les Myopathies, AFM) and a population of 80 million people residing in Germany. More than 30 forms of MD are recognized today caused by different genetic defects. Based on the symptoms of an individual patient the underlying genetic defect cannot be determined, since all MD have the following in common: Muscle fibers are destroyed and become replaced by fatty and fibrous tissue. Various forms of MD are caused by defects of proteins residing in the sarcolemma, the cell membrane of muscle fibers. Other forms are caused by defects of proteins that are associated to the nucleus, to the sarcomer or the cytoplasm. Moreover, there are numerous forms where the exact molecular defect is unknown to date. Even though the underlying defect is known for many MD, the pathogenic process that leads to the decay of musculature is poorly understood. At present, MD cannot be cured. MD are treated by physiotherapy, surgery and medication that may delay progression. Symptomatic therapy such as cardiac pace makers may be life-saving and improve quality of life in many patients. For optimizing research into the MD, a network, the muscular dystrophy network or MD-NET, was initiated and has been supported by the German ministry of education and research (BMBF) since 2003.

Mutations in the gene encoding filamin A as a cause for familial cardiac valvular dystrophy.

BACKGROUND: Myxomatous dystrophy of the cardiac valves affects approximately 3% of the population and remains one of the most common indications for valvular surgery. Familial inheritance has been demonstrated with autosomal and X-linked transmission, but no specific molecular abnormalities have been documented in isolated nonsyndromic forms. We have investigated the genetic causes of X-linked myxomatous valvular dystrophy (XMVD) previously mapped to chromosome Xq28. METHODS AND RESULTS: A familial and genealogical survey led us to expand the size of a large, previously identified family affected by XMVD and to refine the XMVD locus to a 2.5-Mb region. A standard positional cloning approach identified a P637Q mutation in the filamin A (FLNA) gene in all affected members. Two other missense mutations (G288R and V711D) and a 1944-bp genomic deletion coding for exons 16 to 19 in the FLNA gene were identified in 3 additional, smaller, unrelated families affected by valvular dystrophy, which demonstrates the responsibility of FLNA as a cause of XMVD. Among carriers of FLNA mutation, the penetrance of the disease was complete in men and incomplete in women. Female carriers could be mildly affected, and the severity of the disease was highly variable among mutation carriers. CONCLUSIONS: Our data demonstrate that FLNA is the first gene known to cause isolated nonsyndromic MVD. This is the first step to understanding the pathophysiological mechanisms of the disease and to defining pathways that may lead to valvular dystrophy. Screening for FLNA mutations could be important for families affected by XMVD to provide adequate follow-up and genetic counseling.

Novel mutations in LAMA2 gene responsible for a severe phenotype of congenital muscular dystrophy in two Tunisian families.

Congenital muscular dystrophies are a group of common genetically determined disorders often transmitted with a recessive mode of inheritance. In recent years, several deficiencies of proteins from the muscle membrane, extra cellular matrix, sarcomere, muscle cytosol and the nucleus have been described to cause CMD. The occidental type of CMD (MDC1A) in which the primary defect is a deficiency in laminin alpha2 chain (merosin) encoded by LAMA2 gene, accounts for 30-40% of cases. The clinical course of CMD with complete laminin alpha2 chain deficiency may be variable but most often; severe forms characterized by hypotonia at birth, profound muscle weakness, marked delay in motor milestones are observed. Since the identification of the first LAMA2 gene mutations leading to merosin deficiency in 1995, several mutations have subsequently been reported in many exons of this gene without any "hotspot" region. In this work, we report two novel homozygous mutations c.8005delT and c.8244+1G>A in the LAMA2 gene in four Tunisian patients with a severe MDC1A phenotype belonging to two unrelated consanguineous families.

Epidemiological study of muscular disorders in Assiut, Egypt.

Few comprehensive epidemiological studies of the prevalence of muscle diseases have been undertaken, and none has been carried out in our locality. The present cross-sectional study was conducted in Assiut Governorate (Upper Egypt) to estimate the prevalence of different types of primary muscular disorder in 1997. The study involved 52,203 subjects, 15,617 (30%) from the rural community and 36,586 (70%) from the urban community. Patients were identified from a door-to-door survey, and all were subjected to a full clinical examination, with confirmation of the diagnosis through electrophysiological, and biochemical investigations. Histopathological studies were performed for the classification of muscular dystrophies. Forty patients with muscular disorders were identified, with a point prevalence of 76.6 per 100,000 in the total community with no significant differences between the rural and urban communities. The creatine kinase level was abnormally high (>225 IU/l) in 80% of the cases, increased in all patients with muscular dystrophy or myositis, in 88.8% of patients with systemic myopathy and 66.6% of patients with myotonia. None of the cases of myasthenia showed an increase in the creatine kinase level. The lifetime prevalence per 100,000 was 26.8 for muscular dystrophy, 11.49 for myotonia, 11.49 for myositis, 17.24 for systemic myopathy and 9.57 for myasthenia.

Prevalence of the 550delA mutation in calpainopathy (LGMD 2A) in Croatia.

Mutations in the calpain 3 (CAPN3) gene are responsible for limb-girdle muscular dystrophy (LGMD) type 2A. We report five causal mutations: 550delA, DeltaFWSAL, R541W, Y357X and R49H found on 45/50 of alleles studied in 25 unrelated families from Croatia. The 550delA mutation was present on 76% of CAPN3 chromosomes that led us to screen general population for this mutation; 532 random blood samples from three different regions were analyzed using allele-specific PCR. Four healthy 550delA heterozygous were found suggesting a frequency of 1 in 133. All four carriers detected originated from an island and mountain region close to the Adriatic Sea. These findings combined with haplotype analysis confirm that our general population is rather "closed" with a probable founder effect in some parts of the country. In addition, the high frequency of 550delA mutation found in some neighboring European countries together with the easy detection of the 550delA mutation should streamline genetic analysis, especially bearing in mind the geographic and ethnic origin of the patients. Our results, combined with published haplotype studies suggest that 550delA originated in the Eastern Mediterranean from which it has probably spread widely across Europe. Extending this study to other areas would help to address this epidemiological question. Our data are relevant to accurate genetic counseling and patient testing since we lack sensitive and specific biopsy screening methods for detecting patients with calpainopathy. Thus, detection of patients relies on the direct detection of gene mutation and our findings may be helpful in establishing diagnostic screening strategy.

Muscle disorders in pediatric patients in King Chulalongkorn Memorial Hospital.

The authors retrospectively studied histopathologic findings and diagnoses of muscle specimens taken from 188 pediatric patients presenting with clinical neuromuscular disorders in King Chulalongkorn Memorial Hospital between August 1991 and December 2003. Eighty patients (67.8%) established the definite diagnosis by histopathological findings of muscle specimens. About 18.6, 17.7, 7.6, 5.9, 5.0, 3.4, 2.5 and 1.7 percent of the total number of patients were diagnosed as Duchenne muscular dystrophy, spinal muscular atrophy, congenital myopathies, mitochondrial disease, inflammatory myopathies, Becker muscular dystrophy, congenital muscular dystrophy and vacuolar myopathies respectively. Since the histopathological findings in muscle helped to establish the definite diagnosis in most pediatric patients in the present study, thus muscle biopsy is essential for establishing a definite diagnosis in any patient with a suspected neuromuscular disorder.