Facioscapulohumeral muscular dystrophy. Phenotype-genotype correlation in patients with borderline D4Z4 repeat numbers

Facioscapulohumeral muscular dystrophy (FSHD) is associated with a decreased number of D4Z4 repeats on chromosome 4q35. Diagnostic difficulties arise from atypical clinical presentations and from an overlap in D4Z4 numbers between controls and FSHD individuals. Thus, a molecular genetic test result with a borderline D4Z4 number has its limitations for the clinician wanting to differentiate between the diagnosis of FSHD and a myopathy presenting with FSHD-like symptoms.To investigate this problem in more detail we conducted a systematic study of 39 unrelated FSHD patients with borderline D4Z4 repeat numbers and 102 healthy controls. Our aim was threefold: [1] to define the molecular diagnostic cut-off point between FSHD cases and the control population, [2] to describe the myopathic spectrum in patients with borderline D4Z4 repeat numbers and [3] to look for correlations between D4Z4 number and clinical severity.The results indicate that there is no definite D4Z4 diagnostic cut-off point separating FSHD, FSHD-like myopathies and controls. A broad myopathic spectrum with four phenotypes (typical FSHD, facialsparing FSHD, FSHD with atypical features, non-FSHD muscle disease) was found in the borderline region. The expected correlation of D4Z4 repeat number and clinical severity was not found. Therefore the molecular test is of limited help to differentiate FSHD from FSHDlike muscle disorders when the D4Z4 number is n = 8.     

Facioscapulohumeral muscular dystrophy

Facioscapulohumeral muscular dystrophy (FSHD) is a dominantly inherited disorder with an initially restricted pattern of weakness. Early involvement of the facial and scapular stabilizer muscles results in a distinctive clinical presentation. Progression is descending, with subsequent involvement of either the distal anterior leg or hip-girdle muscles. There is wide variability in age at onset, disease severity, and side-to-side symmetry, which is evident even within affected members of the same family. Although FSHD is considered a relatively benign dystrophy by some, as many as 20% of patients eventually become wheelchair-bound. Associated nonskeletal muscle manifestations include high-frequency hearing loss as well as retinal telangiectasias, both of which are rarely symptomatic. The causal genetic lesion in FSHD was described over a decade ago, raising hope that knowledge about its molecular and cellular pathophysiology was soon to follow. In the vast majority of cases, FSHD results from a heterozygous partial deletion of a critical number of repetitive elements (D4Z4) on chromosome 4q35; yet, to date, no causal gene has been identified. The accumulating evidence points to a complex, perhaps unique, molecular genetic mechanism. The absence of detectable expressed sequences from D4Z4, the association of FSHD-causing 4q35 deletions with a specific distal genomic sequence (4qA allele), altered DNA methylation patterns on 4q35, as well as other direct and indirect evidence point to epigenetic mechanisms. As a consequence, partial deletion of D4Z4 results in a (local) chromatin change and ultimately results in the loss of appropriate control of gene expression. There is at present no effective treatment for FSHD. A better understanding of the underlying pathophysiology is needed to design targeted interventions. Despite these limitations, however, two randomized controlled clinical trials have been conducted on FSHD. These trials, along with a previous natural history study, have helped to better define outcome measures for future trials in FSHD as well as other dystrophies.     

Facioscapulohumeral muscular dystrophy functional composite outcome measure

Introduction: We developed an evaluator‐administered functional facioscapulohumeral muscular dystrophy composite outcome measure (FSHD‐COM) comprising patient‐identified areas of functional burden for future clinical trials. Methods: We performed a prospective observational study of 41 patients with FSHD at 2 sites. The FSHD‐COM includes functional assessment of the legs, shoulders and arms, trunk, hands, and balance/mobility. We determined the test‐retest reliability and convergent validity compared to established FSHD disease metrics. Results: The FSHD‐COM demonstrated excellent test‐retest reliability (intraclass correlation coefficient [ICC] 0.96; subscale ICC range, 0.90–0.94). Cross‐sectional associations between the FSHD‐COM and disease duration, clinical severity, and strength were moderate to strong (Pearson correlation coefficient range |0.51–0.92|). Discussion: The FSHD‐COM is a disease‐relevant, functional composite outcome measure suitable for future FSHD clinical trials that shows excellent test‐retest reliability and cross‐sectional associations to disease measures. Future directions include determining multisite reliability, sensitivity to change, and the minimal clinically important change in the FSHD‐COM. Muscle Nerve 58 : 72–78, 2018     

Molecular genetics of facioscapulohumeral muscular dystrophy

Facioscapulohumeral muscular dystrophy (FSHD) is an autosomal dominant neuromuscular disorder. The disease affects specific muscles of the face, shoulder-girdle and upper arm. The biochemical defect underlying FSHD is unknown and there are no specific tests that are diagnostic of FSHD. Genetic linkage studies have mapped the FSHD gene to chromosome 4q35. A DNA marker (p13E-11; D4F104S1, formerly D4S810) has been isolated which recognizes two highly polymorphic loci detectable by EcoRI or HindIII; one locus maps to chromosome 4q35 and shows fragments between about 50 and 320 kb. In FSHD patients deletions occur within this EcoRI/HindIII fragment, yielding fragments that are usually smaller than 28 kb. Characterization of the polymorphic fragments demonstrates that they consist of a 3.2 kb tandem repeat; their number can range between approximately 12 and 96 within the 4q35-specific fragments. In FSHD patients, an integral number of these tandem repeats are deleted, leaving at maximum eight copies.     

Prednisone 10 days on/10 days off in patients with Duchenne muscular dystrophy

Corticosteroids are effective in improving motor function in Duchenne muscular dystrophy (DMD) patients within 6 months–2 years of treatment initiation, but there is as yet no consensus on which treatment scheme is the best. We retrospectively analyzed data of 35 DMD patients who were treated with prednisone 0.75 mg/kg per day intermittently 10 days on/10 days off. Prednisone was started during the ambulant phase at age 3.5–9.7 years (median 6.5 years). The median period of treatment was 27 months (range 3–123 months). The median age at which ambulation was lost was 10.8 years (mean 10.9 years; 95% confidence interval 10.0–11.8 years). Nine patients (26%) had excessive weight gain. Eight boys (21%) had a bone fracture, which was when four of these eight children lost the ability to walk. Treatment was stopped in two obese patients, two hyperactive boys and one patient following a fracture. Our data suggest that prednisone 10 on/10 off has relatively few side effects and extends the ambulant phase by 1 year compared to historical controls.     

Linkage studies in autosomal dominant facioscapulohumeral muscular dystrophy

Linkage studies were undertaken in 120 individuals from 10 kindreds with autosomal dominant facioscapulohumeral muscular dystrophy using 35 different marker genes. No linkage was found. The highest lod score was 1.438 for the immunoglobulin heavy chain gene cluster (IGH) at a recombination fraction of 0.2. IGH is located on the long arm of chromosome 14. Based on scores of other marker genes and on a recombination map of chromosome 14, the probability that the gene for facioscapulohumeral muscular dystrophy is located on chromosome 14 is estimated to be approximately 6%.     

Rimmed vacuoles in facioscapulohumeral muscular dystrophy: a unique ultrastructural feature

Rimmed vacuoles (RV) are a characteristic pathological feature in inclusion body myositis, but may also occur in other neuromuscular disorders, such as distal myopathies, oculopharyngeal myopathy, polymyositis, rigid spine syndrome, congenital myopathies, and some limb girdle muscular dystrophies, as well as in various neurogenic diseases. We describe a patient with RV in familial facioscapulohumeral muscular dystrophy (FSHD) associated with an FSHD-typical deletion on chromosome 4q35. Thus, FSHD should be included in the differential diagnosis of neuromuscular disorders with RV.     

Dystrophin在不同类型肌营养不良症中的变化及诊断价值

目的研究dystrophin在不同类型肌营养不良症中的变化及分型诊断价值.方法用抗dystrophin抗体对107例肌营养不良症患者肌组织标本行免疫组织化学分析.结果Duchenne型肌营养不良(DMD)患者肌细胞膜上无显色,Becker型肌营养不良(BMD)患者肌细胞膜上显色浅淡、不连续或呈斑片状.肢带型肌营养不良(LGMD)患者肌细胞膜上染色正常.结论dystrophin免疫组化染色对于年龄较小临床不易区分的DMD/BMD患者,可区分开来,以早期预测功能影响程度.该方法也有助于区分临床表现相似的成年散发BMD和LGMD患者,对于正确地进行遗传咨询具有重要意义.     

Exome sequencing identifies a novel SMCHD1 mutation in facioscapulohumeral muscular dystrophy 2

FSHD2 is a rare form of facioscapulohumeral muscular dystrophy (FSHD) characterized by the absence of a contraction in the D4Z4 macrosatellite repeat region on chromosome 4q35 that is the hallmark of FSHD1. However, hypomethylation of this region is common to both subtypes. Recently, mutations in SMCHD1 combined with a permissive 4q35 allele were reported to cause FSHD2. We identified a novel p.Lys275del SMCHD1 mutation in a family affected with FSHD2 using whole-exome sequencing and linkage analysis. This mutation alters a highly conserved amino acid in the ATPase domain of SMCHD1. Subject III-11 is a male who developed asymmetrical muscle weakness characteristic of FSHD at 13 years. Physical examination revealed marked bilateral atrophy at biceps brachii, bilateral scapular winging, some asymmetrical weakness at tibialis anterior and peroneal muscles, and mild lower facial weakness. Biopsy of biceps brachii in subject II-5, the father of III-11, demonstrated lobulated fibers and dystrophic changes. Endomysial and perivascular inflammation was found, which has been reported in FSHD1 but not FSHD2. Given the previous report of SMCHD1 mutations in FSHD2 and the clinical presentations consistent with the FSHD phenotype, we conclude that the SMCHD1 mutation is the likely cause of the disease in this family.     

Severe muscular dystrophy in girls

Twelve girls and 2 boys with severe but not congenital muscular dystrophy were found in a national survey. An autosomal recessive gene is likely to account for most if not all of these cases. The condition differs slightly from X-linked Duchenne muscular dystrophy in showing prominent early toe-walking, a milder course, relatively more weakness of the deltoid muscles, normal intelligence, a normal ECG and a more focal pattern of muscle pathology.     

面肩肱型肌营养不良症1A的基因型与表型关系研究

目的探讨面肩肱型肌营养不良症(FSHD)1A的基因型与临床表型之间的相关关系。方法对来自33个无关家系的50名临床诊断FSHD的患者进行EcoRⅠ BlnⅠ双酶切基因诊断以及临床表型评分,应用Spearman秩相关方法分析FSHD1A基因诊断的EcoRⅠ BlnⅠ/p13E-11DNA片段大小与临床表型评分之间的相关性。结果50名FSHD患者的基因诊断结果为EcoRⅠ BlnⅠ/p13E-11DNA片段大小介于10￣33.5kb,平均(17.70±6.628)kb,其中同一家系中不同患者的基因诊断结果相同。对33个家系各取一名患者的基因诊断结果与临床表型评分做相关分析,R=-0.34,P=0.03。校正控制年龄因素后做偏相关分析,R=-0.3775,P=0.017。结论EcoRⅠ BlnⅠ/p13E-11DNA片段大小与FSHD1A的临床表型之间具有负相关性,它在判断FSHD1A病情预后以及遗传咨询方面具有重要参考价值。     

Immunohistochemical study of calpain and its endogenous inhibitor in the skeletal muscle of muscular dystrophy

A calcium-dependent proteinase (calpain) has been suggested to play an important role in muscle degradation in Duchenne muscular dystrophy (DMD). In immunohistochemical studies, calpain and its endogenous inhibitor (calpastatin) were located exclusively in the cytoplasm in normal human muscles. The intensity of the staining was stronger in type 1 than in type 2 fibers. Quantitative immunohistochemical study showed an increase of calpain in biopsied muscles from the patients with DMD and Becker muscular dystrophy. Abnormal increases in calpain and calpastatin were demonstrated mainly in atrophic fibers, whereas necrotic fibers showed moderate or weak immunoreactions for the enzymes. Opaque fibers and hypertrophic fibers were negative. Not all dystrophin-deficient muscle fibers necessarily showed a strong reaction for calpain. We suggest that calpain may play an important role in muscle fiber degradation, especially in the early stage of muscle degradation in muscular dystrophy.     

Cardiac transplantation in female Emery-Dreifuss muscular dystrophy

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

Facioscapulohumeral muscular dystrophy: a prospective study of weakness and functional impairment

Only isolated prospective studies have attempted to chart the natural history of facioascapulohumeral muscular dystrophy (FSHD), a benign myopathy with notoriously variable clinical manifestations and progression. This 10-year prospective study was performed to document by simple clinical methods the natural history of 16 patients with moderately advanced FSHD. Limb strength was evaluated by the bedside manual muscle test. Global weakness was documented as a composite average muscle score (AMS). Limb function was evaluated by a non-linear grading system of important functional milestones. A scale of activities of daily living (ADL) was used to assess disability across multiple functional domains in a home environment. Six-monthly evaluations determined a linear deterioration of the mean AMS that reached statistical significance from baseline at the 5-year interval. Half of patients showed a functional decline of the arms by one grade. All patients maintained useful hand function. Three quarters of patients suffered functional decline of the legs, commonly by one grade. All patients remained ambulant. Interval analyses showed a linear deterioration of the mean ADL score that reached statistical significance from baseline at the 5-year interval. Functional deterioration was mostly due to impaired shoulder girdle activities. This study of a relatively homogeneous subgroup of FSHD patients showed a predictable rate of clinical progression in a muscle disease with a notoriously variable clinical presentation and outcome. Natural history data obtained in this study could serve as positive controls for future therapeutic trials in this patient population. The chosen clinical parameters proved useful tools for charting clinical disease progression. Functional tests proved advantageous, because decline was based partly on patient self-reports, thereby improving time and cost effectiveness.     

50例面肩肱型肌营养不良症的基因诊断与临床特征

目的对面肩肱型肌营养不良症(FSHD)患者进行基因诊断并总结其临床特征,以提高FSHD的诊断水平。方法以p13E-11为探针用EcoRⅠ BinⅠ双酶切的Southern杂交方法对50例FSHD患者进行基因诊断,并对其临床特征进行总结。结果50例FSHD患者的基因诊断结果为EcoRⅠ BinⅠ/p13E-11片段大小介于10～33．5 kb,平均(17．70±6．628)kb。家族遗传性患者符合常染色体显性遗传特点。FSHD多在青少年期慢性起病,病情缓慢进展；选择性侵犯面肌、肩带肌和上臂肌,部分患者逐渐累及盆带肌和下肢肌肉,患肌常不对称受累；血清CK水平正常或轻中度增高,肌电图示肌源性损害,肌活检呈肌病特征。结论以p13E-11为探针用EcoRⅠ BinⅠ双酶切的Southern杂交方法可对FSHD患者进行基因诊断,识别FSHD的临床特征以及进行基因诊断可提高FSHD的诊断水平。     

重视Duchenne型肌营养不良症的康复治疗

康复治疗对改善Duchenne型肌营养不良症患者生活质量、延缓病情进展至关重要,一些国家业已制定了康复治疗指南,我国尚缺乏这方面的指导性研究和意见。为了提高临床医师对该病症康复治疗的认识,现对其病情分期、临床特征,以及康复治疗的一般原则、常用方法和注意事项进行概述,为临床康复治疗提供一些参考。     

强直性肌营养不良症患者肌肉病理学特点研究

目的 探讨强直性肌营养不良症患者肌肉病变的病理学特点。方法 选择1986—2003年经临床和肌电图检查明确诊断的14例强直性肌营养不良症患者，采用开放性活检手术方法获得肱二头肌肌肉标本，分别进行苏木素-伊红（HE）、改良Gomofi三色（MGT）、高碘酸Schiff反应（PAS）、油红“O”（ORO）、还原型辅酶Ⅰ-四氮唑还原酶（NADH-TR）、非特异性酯酶（NSE）及ATP酶等多种组织化学染色，并于光学显微镜下观察肌肉组织的病理学变化特点。结果 HE染色显示，14例患者肌纤维直径大小不一，但肌纤维萎缩的数量及形态不同，其中7例萎缩的肌纤维呈角状或长条形；5例呈小圆形；2例小角状与小圆形萎缩的肌纤维混合存在，数量相近。但变性及坏死性改变均不明显。有5例患者可见典型的类圆形、弧形、三角形或梭形肌质块，位于肌纤维中央、外周、一角或一侧，其形态与在肌纤维中所处的位置有关。肌质块具有如下特点：HE染色呈紫红色团块状结构；改良Gomofi三色染色呈深蓝色，且可伴有红染，呈不典型性破碎红纤维，并可见线粒体数量增加；高碘酸Schiff反应、非特异性酯酶、还原型辅酶Ⅰ-四氮唑还原酶等酶反应活性明显增强；ATP酶染色显示14例患者中11例肌纤维有其优势性，呈明显的肌源性群组化现象，6例为Ⅰ型肌纤维优势，5例呈Ⅱ型肌纤维优势；3例肌纤维分型正常。结论 肌质块及肌源性群组化为强直性肌营养不良症肌肉病变的病理学特点。     

Freeze fracture studies of muscle plasma membrane in human muscular dystrophy

Summary Freeze fracture analysis of intramembranous particle density in skeletal muscle plasma membrane from 7 patients with Duchenne muscular dystrophy (DMD), 5 patients with facioscapulohumeral muscular dystrophy (FSH) and 5 patients with myotonic dystrophy (MyD) were carried out. Marked deplction of intramembranous particles including orthogonal arrays were significantly decreased in FSH. No abnormalities were noted in MyD.This work was supported by a Research Center Grant from the Muscular Dystrophy Association of America and by grants NS-08075, NS-14471 and 5 M01 RR00040 from the U.S. Public Health Service