Findings of limb-girdle muscular dystrophy R7 telethonin-related patients from a Chinese neuromuscular center

neurogenetics - Limb-girdle muscular dystrophy (LGMD) is a group of clinically and genetically heterogeneous neuromuscular disorders. LGMD-R7, which is caused by telethonin gene (TCAP) mutations,...     

一个肢带型肌营养不良家系的临床和分子遗传学分析

目的 研究1个肢带型肌营养不良(limb girdle muscular dystrophy,LGMD)家系的临床表现,并应用基因突变分析、基因组扫描技术和连锁分析对该家系进行分子遗传学分析.方法 对1个来自浙江的连续4代发病的LGMD家系进行家系调查和体格检查,先证者行电生理检查及肌肉病理活体组织检查分析;26名家系成员在知情同意的情况下抽取基因组DNA进行基因突变分析、基因组扫描和连锁分析.结果 家系分析证明该家系符合常染色体显性遗传,家系中存在遗传早现现象,主要表现为四肢近端肌无力,无构音障碍、肌强直;电生理检查和肌肉活体组织检查符合肌肉病变特点;基因突变分析未发现LGMD1A、1B、1C和面肩肱型肌营养不良(FSHD)基因的致病突变;基因组扫描和连锁分析显示该家系致病基因与已报道的LGMD1D和LGMD1F的染色体区间连锁关系不成立.结论 LGMD家系患者的临床表现具有高度异质性,该家系的致病基因不在已报道的位点内,推测可能存在新的致病位点或是一种新的LGMD遗传类型.     

Miyoshi myopathy and limb girdle muscular dystrophy R2 are the same disease

This study aims to determine clinically relevant phenotypic differences between the two most common phenotypic classifications in dysferlinopathy, limb girdle muscular dystrophy R2 (LGMDR2) and Miyoshi myopathy (MMD1). LGMDR2 and MMD1 are reported to involve different muscles, with LGMDR2 showing predominant limb girdle weakness and MMD1 showing predominant distal lower limb weakness. We used heatmaps, regression analysis and principle component analysis of functional and Magnetic Resonance Imaging data to perform a cross-sectional review of the pattern of muscle involvement in 168 patients from the Jain Foundation's international Clinical Outcomes Study for Dysferlinopathy. We demonstrated that there is no clinically relevant difference in proximal vs distal involvement between diagnosis. There is a continuum of distal involvement at any given degree of proximal involvement and patients do not fall into discrete distally or proximally affected groups. There appeared to be geographical preference for a particular diagnosis, with MMD1 being more common in Japan and LGMDR2 in Europe and the USA. We conclude that the dysferlinopathies do not form two distinct phenotypic groups and therefore should not be split into separate cohorts of LGMDR2 and MM for the purposes of clinical management, enrolment in clinical trials or access to subsequent treatments.     

Concurrence of limb girdle muscular dystrophy and myasthenia gravis

We describe a case of limb girdle muscular dystrophy with associated myasthenia gravis. This association has not been previously noted in the literature. The unusual feature of the case was that symptoms coexisted for several years before a correct diagnosis was made. The diagnosis was based on the clinical picture and the results of the muscle biopsy and electrophysiologic testing. This case serves to illustrate the fact that a separate problem should be considered when the clinical picture is not compatible with the underlying diagnosis.     

Sarcoglycanopathies in Dutch patients with autosomal recessive limb girdle muscular dystrophy

Within a group of 76 sporadic/autosomal recessive limb girdle muscular dystrophy (LGMD) patients we tried to identify those with LGMD type 2C-E. Muscle biopsy specimens of 40 index patients, who had 22 affected sibs, were analyzed immuno-histochemically for the presence of three subunits: α-, β-, and γ,-sarcoglycans. Abnormal sarcoglycan expression was established in eight patients, with six affected sibs. In one patient γ-sarcoglycan was absent, and both α- and β-sarcoglycans were reduced. In the remaining seven patients γ-sarcoglycan was (slightly) reduced, and α- and β-sarcoglycans were absent or reduced. By DNA sequencing mutations were detected in one of the three sarcoglycan genes in all eight cases. Three patients had mutations in the α-, three in the β-, and two in the γ-sarcoglycan gene. The patients with sarcoglycanopathy comprised the more severely affected cases (P=0.04). In conclusion, sarcoglycanopathy was identified in 23% (14/62) of the autosomal recessive LGMD patients. Received: 11 November 1999, Received in revised form: 27 January 2000, Accepted: 29 February 2000     

D uchenne 型肌营养不良家系的临床及分子遗传学研究

目的：探讨Duchenne型肌营养不良（DMD）家系的临床及分子遗传学特征。方法收集并分析我院收治的2个DMD家系临床资料和基因检测结果,并结合既往相关文献,回顾该病在临床表现、分子遗传学等方面的特点。结果DMD儿童期隐匿起病,进行性加重,以肌无力、肌萎缩为特点,可伴肌肉假性肥大,血清肌酶水平异常增高,肌电图呈肌源性损害,肌肉活检呈肌病特征。本文报道的2个家系经基因检测家系1先证者为DMD基因的第3～21号外显子缺失,家系2先证者则为第8、9外显子重复突变,2个家系中的先证者基因均为纯合突变,且其母亲均为致病基因的携带者,符合X染色体隐性遗传的规律。结论早期识别DMD的临床特征有助于提高该病的诊断水平,基因检测是一种确诊DMD快速、有效的方法。     

Efficient identification of novel mutations in patients with limb girdle muscular dystrophy

Limb girdle muscular dystrophy type 2 (LGMD2) is a genetically heterogeneous autosomal recessive disorder caused by mutations in 15 known genes. DNA sequencing of all candidate genes can be expensive and laborious, whereas a selective sequencing approach often fails to provide a molecular diagnosis. We aimed to efficiently identify pathogenic mutations via homozygosity mapping in a population in which the genetics of LGMD2 has not been well characterized. Thirteen consanguineous families containing a proband with LGMD2 were recruited from Saudi Arabia, and for 11 of these families, selected individuals were genotyped at 10,204 single nucleotide polymorphisms. Linkage analysis excluded all but one or two known genes in ten of 11 genotyped families, and haplotype comparisons between families allowed further reduction in the number of candidate genes that were screened. Mutations were identified by DNA sequencing in all 13 families, including five novel mutations in four genes, by sequencing at most two genes per family. One family was reclassified as having a different myopathy based on genetic and clinical data after linkage analysis excluded all known LGMD2 genes. LGMD2 subtypes A and B were notably absent from our sample of patients, indicating that the distribution of LGMD2 mutations in Saudi Arabian families may be different than in other populations. Our data demonstrate that homozygosity mapping in consanguineous pedigrees offers a more efficient means of discovering mutations that cause heterogeneous disorders than comprehensive sequencing of known candidate genes.     

Patient reported quality of life in limb girdle muscular dystrophy

This study determined the frequency and impact of symptoms on quality of life in patients diagnosed with limb girdle muscular dystrophy (LGMD). Participants with a diagnosis of LGMD in registries based at the Coalition to Cure Calpain-3, the Jain foundation, and the Global FKRP Registry competed a survey to report the frequency and relative impact of themes and symptoms of LGMD. Frequency, mean impact, and population impact scores were calculated, and responses were categorized by age, symptom duration, gender, employment status, use of assistive devices, and LGMD subtypes. 134 participants completed the survey. The most prevalent themes included an inability to do activities (100%), limitation with mobility (99.3%), and lower extremity weakness (97.0%). Themes with the greatest impact were: limitations with mobility, lower extremity weakness, and an inability to do activities. Symptom duration and the use of assistive devices were associated with the presence of multiple themes. Employment was associated with the impact of several themes with no differences in frequency. The prevalence and impact of these themes vary in the LMGD population. The most prevalent and impactful themes were related to weakness, but additional concerns related to emotional challenges should also be considered in clinical and research settings.     

Myoneuropathic presentation of limb girdle muscular dystrophy R8 with a novel TRIM32 mutation

TRIM 32-related Limb Girdle Muscular Dystrophy (LGMD R8/2H) is a rare genetic muscle disease reported in fewer than 100 patients worldwide. Here, we report a male patient with progressive proximo-distal lower limb weakness with onset in the third decade who had mixed myopathic and neurogenic pattern in electrophysiology and muscle biopsy. Clinical exome sequencing revealed a homozygous pathogenic single base pair insertion in exon 2 of the TRIM32 gene confirming the diagnosis of LGMD R8. This is a novel frameshift mutation and one of the very few cases of LGMD R8 reported from India.     

The RAGE pathway in inflammatory myopathies and limb girdle muscular dystrophy

Oxidative stress and nuclear factor-B (NF-B) activation are linked to the pathogenesis of many metabolic, degenerative, and chronic inflammatory diseases. Activation of the receptor for advanced glycation end products (RAGE) by its specific ligand N-carboxymethyllysine (CML) results in the activation of NF-B and the production of proinflammatory cytokines. To determine whether engagement of RAGE contributes to the pathogenesis of inflammatory myopathies, we performed immunohistochemical studies on the presence of CML-modified proteins, RAGE and activated NF-B in muscle biopsies of patients with polymyositis (PM, n=10), dermatomyositis (DM, n=10), limb girdle muscular dystrophy (LGMD, n=10) and in 10 controls with normal muscle biopsy results. In inflammatory myopathies CML, RAGE and NF-B were detected in mononuclear cells and in regenerating muscle fibers. CML, NF-B and, to a lesser extent, RAGE were also found in degenerating muscle fibers, but colocalization of CML, RAGE and NF-B was only seen in infiltrating mononuclear cells and regenerating muscle fibers. Immunofluorescence double labeling demonstrated an expression of CML, RAGE and NF-B in CD4-, CD8-, CD22- and CD68-positive mononuclear cells. Western blot analysis showed an increased immunoreactivity for CML-modified proteins in PM and DM. In LGMD, CML, RAGE and NF-B were found in regenerating muscle fibers and less frequently in degenerating muscle fibers, and with lower staining intensities than in inflammatory myopathies. Our data suggests that the CML-RAGE-NF-B pathway is an evident proinflammatory pathomechanism in mononuclear effector cells in PM and DM. RAGE-mediated NF-B activation may be involved in muscle fiber regeneration in inflammatory myopathies and LGMD.     

Multisystem disorder and limb girdle muscular dystrophy caused by LMNA p.R28W mutation

Primary laminopathies caused by mutations in the LMNA gene typically display an extremely pleiotropic clinical presentation including cardiac, muscular and metabolic phenotypes. Additionally, many atypical laminopathies have been described combining features of two or more of the distinctive disorders or syndromes associated with LMNA mutations. We report on a 46-year-old female patient with a heterozygous p.R28W LMNA mutation, who presented with a novel clinical phenotype comprising severe limb-girdle muscular dystrophy, pronounced partial lipodystrophy, cardiac conduction defect, polycystic ovary disease and a metabolic syndrome with insulin-resistant diabetes mellitus and hypertriglyceridemia. On examination, her 23-year old daughter solely showed early signs of a LGMD phenotype.     

Asian patients with limb girdle muscular dystrophy 2I (LGMD2I)

Limb girdle muscular dystrophy type 2I (LGMD2I) is caused by defects in the fukutin-related protein (FKRP) gene. In most Caucasian patients with LGMD2I, the condition is associated with a missense mutation - c.826C>A (p.Leu276Ile). We describe two Chinese brothers with progressive shoulder and pelvic muscle weakness. They had muscle stiffness and myalgia after exercise, but lacked obvious hypertrophy of the calves. Muscle biopsy showed dystrophic features with many rimmed vacuoles in the fibers. Immunohistochemistry and immunoblot analyses revealed reductions of alpha-(??)-dystroglycan (VIA4-1) and laminin-??2 (80-kDa C-terminal and 300-kDa N-terminal). Two novel heterozygous mutations (c.208T>A and c.1030G>T) in the FKRP gene were identified in these patients. In addition, we summarise the clinical features of patients with LGMD2I in the Asian region. Our findings might indicate that the pathogenic FKRP mutations in Asian patients with LGMD2I are sporadic compound heterozygous mutations rather than the hot-spot c.826C>A mutation seen in Caucasian populations.     

Protein and genetic diagnosis of limb girdle muscular dystrophy type 2A: The yield and the pitfalls

Limb girdle muscular dystrophy type 2A (LGMD2A) is the most frequent form of LGMD worldwide. Comprehensive clinical assessment and laboratory testing is essential for diagnosis of LGMD2A. Muscle immunoblot analysis of calpain‐3 is the most useful tool to direct genetic testing, as detection of calpain‐3 deficiency has high diagnostic value. However, calpain‐3 immunoblot testing lacks sensitivity in about 30% of cases due to gene mutations that inactivate the enzyme. The best diagnostic strategy should be determined on a case‐by‐case basis, depending on which tissues are available, and which molecular and/or genetic methods are adopted. In this work we survey the current knowledge, advantages, limitations, and pitfalls of protein testing and mutation detection in LGMD2A and provide an update of genetic epidemiology. Muscle Nerve 52 : 163–173, 2015     

The frequency of limb girdle muscular dystrophy 2A in northeastern Italy

Limb-girdle muscular dystrophy 2A (LGMD2A) is considered to be the most frequent LGMD. Our study surveyed an area in northeastern Italy where an almost complete ascertainment was possible. To identify LGMD2A patients we used a new diagnostic approach, including several molecular and biochemical methods. In 84 screened patients from northeastern Italy, we identified 39 LGMD2A patients, the prevalence of LGMD2A being 9.47 per million. In the Venezia district it appears higher than in other districts of the Veneto region, and in the Friuli region it is three times higher than in Veneto, due to the recurrence of single mutation. Haplotype analysis suggested a founder effect. The population from Venezia and Friuli has a higher risk of being heterozygote for these two mutant alleles than people from the rest of northeastern Italy. Our results indicate that LGMD2A is one of the most frequent autosomal recessive disorders, thus finding its molecular characterization becoming increasingly important.     

Spin-lock magnetic resonance imaging of muscle in patients with autosomal recessive limb girdle muscular dystrophy.

Spin-lock imaging is a new magnetic resonance imaging (MRI) technique used to reflect the microstructural integrity of muscle. The purpose of this study was to characterize spin-lock contrast (SLC) of calf muscles in limb girdle muscular dystrophy (LGMD). The calf muscles of 5 patients with LGMD and 10 healthy volunteers were imaged with an off-resonance magnetic resonance (MR) spin-lock suppression pulse. Spin-lock suppression ratios were calculated for anterior tibialis, posterior tibialis, soleus, and gastrocnemius muscles. Clinical assessments of muscle strength were compared to the spin-lock suppression ratios in the LGMD group. Strong SLC was observed in healthy muscles, with mean (+/- SD) suppression ratios ranging from 51.2% (+/- 3.6%) to 56.3% (+/- 1.3%). In diseased muscle, spin-lock signal suppression was reduced by 8%-70%, demonstrating an inverse correlation between symptom duration and suppression ratios. Spin-lock contrast in the patients with LGMD, as a reflection of tissue integrity, was best preserved in posterior tibialis, anterior tibialis, soleus, and gastrocnemius muscles in descending order. Clinical assessments did a poorer job of differentiating than SLC did and were in poor agreement with spin-lock suppression ratios. Spin-lock MRI can quantify microstructural changes in LGMD and appears to provide information not obtainable from clinical evaluations. This suggests that this noninvasive technique may be useful in evaluating the extent, progression, and response to therapy of LGMD.     

A new mutation of the fukutin gene causing late-onset limb girdle muscular dystrophy

Defects in glycosylations of α-dystroglycan are associated with mutations in several genes, including the fukutin gene (FKTN). Hypoglycosylation of α-dystroglycan results in several forms of muscular dystrophy with variable phenotype. Outside Japan, the prevalence of muscular dystrophies related to aberrations of FKTN is rare, with only eight reported cases of limb girdle phenotype (LGMD2M). We describe the mildest affected patient outside Japan with genetically confirmed LGMD2M and onset of symptoms at age 14. She was brought to medical attention at age 12, not because of muscle weakness, but due to episodes of tachycardia caused by Wolff–Parkinson–White syndrome. On examination, she had rigid spine syndrome, a typical limb girdle dystrophy pattern of muscle weakness, cardiomyopathy, and serum CK levels >2000 IU/L (normal <150 IU/L). A homozygous, novel c.917A>G; p.Y306C mutation in the FKTN gene was found. The case confirms FKTN mutations as a cause of LGMD2M without mental retardation and expands the phenotypic spectrum for LGMD2M to include cardiomyopathy and rigid spine syndrome in the mildest affected non-Japanese patient reported so far.