Diagnosis and management of spinal muscular atrophy: Part 1: Recommendations for diagnosis,rehabilitation, orthopedic and nutritional care

Spinal muscular atrophy (SMA) is a severe neuromuscular disorder due to a defect in the survival motor neuron 1 (SMN1) gene. Its incidence is approximately 1 in 11,000 live births. In 2007, an International Conference on the Standard of Care for SMA published a consensus statement on SMA standard of care that has been widely used throughout the world. Here we report a two-part update of the topics covered in the previous recommendations. In part 1 we present the methods used to achieve these recommendations, and an update on diagnosis, rehabilitation, orthopedic and spinal management; and nutritional, swallowing and gastrointestinal management. Pulmonary management, acute care, other organ involvement, ethical issues, medications, and the impact of new treatments for SMA are discussed in part 2.     

IQ, prognosis and Duchenne muscular dystrophy

The verbal scales (VS-IQ) of the IQs of 25 boys with Duchenne muscular dystrophy, the total population in Western Australia older than five yrs, were recorded. All the results of those 20 yrs of age and older lay within the normal range. The mean VS-IQ of those less than 20 yrs and less than 18 yrs is compared with the mean VS-IQ of those 20 yrs and older, and 18 yrs and older, respectively. The differences between the groups are statistically significant, and it is postulated that an active management programme has revealed a population of boys with normal intelligence who have an increased chance of prolonged survival.     

假肥大型肌营养不良的诊治与生存质量分析

目的 分析西南地区假肥大型肌营养不良(Duchenne/Becker muscular dystrophy,DMD/BMD)患儿的诊治现状及生存质量,以提高诊疗水平.方法 294例疑诊病例采用多重聚合酶链反应(multiple polymerase chain reaction,mPCR)与短串联重复序列(short tandem repeat,STR)多态性连锁分析法行Dystrophin基因检测;17例阴性病例行腓肠肌活检.翻译、修订儿童生存质量量表PedsQLTM 3.0神经肌肉疾病模块(pediatric quality of life inventoryTM 3.0 neuromuscular module,PedsQLTM 3.0 NMM),并调查39例确诊病例的生存质量.随访治疗情况.结果 294例疑诊病例Dystrophin基因缺失的阳性率为32.65％.17例病理活检的阳性率为82.35％.39例确诊病例的病情越重,PedsQLTM 3.0 NMM中文版疾病维度评分越低(P＜ 0.05);交流、家庭维度评分普遍较低(P＞0.05).18例DMD患儿行口服泼尼松0.75 mg/(kg·d)治疗.结论 mPCR+ STR法可提高Dystrophin基因检测的准确性,但阳性率不高;肌肉活检是确诊手段的良好补充.病情轻重是影响DMD/BMD患儿生存质量的主要因素;他们普遍缺乏良好的交流,家庭经济条件较差.制定适合我国国情的DMD/BMD诊治指南尤为迫切.     

Dystrophin analysis in the differential diagnosis of autosomal recessive muscular dystrophy of childhood and Duchenne muscular dystrophy

We report 2 patients with childhood autosomal recessive muscular dystrophy. Both patients had slight muscle weakness without enlargement of the calf muscles or involvement of the facial muscles. Their clinical courses are static. Muscle histology revealed characteristic features of muscular dystrophy. Dystrophin was identifiable in the sarcolemma of both patients by immunocytochemical staining with an antidystrophin antibody. At an early age, immunocytochemical analysis with antidystrophin antibody was useful in distinguishing between childhood autosomal recessive and Duchenne muscular dystrophies.     

Diagnosis and management of Duchenne muscular dystrophy in a developing country over a 10-year period

Clinical data on Duchenne muscular dystrophy (DMD) are lacking in developing countries. The objective of this study was to delineate the demographic characteristics, investigations, and outcome of 21 Malaysian males diagnosed with DMD over a period of 10 years. Mean age presentation was 3 years 8 months (SD 23mo; range 10 to 84mo), mean duration from first presentation to diagnosis was 3y 7mo (SD 26mo; range 5 to 84) and the mean age for loss of ambulation was 11 years (SD 25mo; range 102 to 168). There was family history of DMD in five of the 21 patients. Muscle biopsy showed confirmatory findings of DMD in the 16 patients tested. Molecular genetic analysis showed dystrophin gene deletions in 11 of these 16 patients. Four and seven of the students stopped schooling and had learning difficulties, respectively; only nine had satisfactory school performances. Eight out of 14 patients evaluated were classified as having severe to total dependency levels on the modified Barthel Index for activities of daily living assessment. DMD is associated with significant medical and social needs for a developing country such as Malaysia. Earlier referral, genetic counselling, and provision of support and rehabilitative services are the main priorities.     

假肥大型肌营养不良症40例临床特征与基因诊断

目的对假肥大型肌营养不良症（DMD／BMD）患者总结其临床特征并进行基因诊断,以提高对DMD／BMD疾病的认识及诊断水平。方法对40例DMD／BMD患者临床特征进行总结包括临床表现、血清肌酶、肌电图及肌肉活检等,并应用18对引物多重PCR的方法对其进行Dystrophin基因缺失诊断。结果DMD／BMD为儿童期隐匿起病、缓慢进行性加重,以肌无力和肌萎缩为特点,主要选择性侵犯四肢近端肌、盆带肌、腰带肌等,可有肌肉假性肥大,有些患者可有智能减退和心肌损害;血清肌酶水平异常增高,肌电图示肌源性损害,肌肉活检呈肌病特征。基因诊断27例存在外显子片段缺失,13例未检测到缺失。结论识别DMD／BMD的临床特征有助于提高对其的诊断水平,多重PCR作为一种简便快速的诊断方法可对DMD／BMD患者进行基因诊断。     

Clinical management of Duchenne muscular dystrophy: the state of the art

Introduction

Duchenne muscular dystrophy (DMD) is a devastating, progressive neuromuscular disorder for which there is no cure. As the dystrophin gene is located on the X chromosome, DMD occurs predominately in males. DMD is caused by a lack of functional dystrophin protein resulting from mutations in the 2.2-Mb DMD gene, whichdisrupts the reading frame. Care considerations for DMD advocate a coordinated, multidisciplinary approach to the management of DMD in order to optimize management of the primary manifestations of DMD as well as any secondary complications that may arise.

Methods

This review provides an overview of the multidisciplinary clinical management of DMD with regard to the respiratory, cardiology, orthopedic, and nutritional needs of patients with DMD. Recent advances in novel disease-modifying treatments for DMD are also discussed with specific reference to exon skipping and suppression of premature stop codons as promising genetic therapies.

Results

The combination of multidisciplinary clinical management alongside novel gene therapiesoffers physicians a powerful armamentarium for the treatment of DMD.

     

Characterization of neuromuscular synapse function abnormalities in multiple Duchenne muscular dystrophy mouse models

Duchenne muscular dystrophy (DMD) is an X‐linked myopathy caused by dystrophin deficiency. Dystrophin is present intracellularly at the sarcolemma, connecting actin to the dystrophin‐associated glycoprotein complex. Interestingly, it is enriched postsynaptically at the neuromuscular junction (NMJ), but its synaptic function is largely unknown. Utrophin, a dystrophin homologue, is also concentrated at the NMJ, and upregulated in DMD. It is possible that the absence of dystrophin at NMJs in DMD causes neuromuscular transmission defects that aggravate muscle weakness. We studied NMJ function in mdx mice (lacking dystrophin) and wild type mice. In addition, mdx/utrn^+/? and mdx/utrn^?/? mice (lacking utrophin) were used to investigate influences of utrophin levels. The three Duchenne mouse models showed muscle weakness when comparatively tested in vivo, with mdx/utrn^?/? mice being weakest. Ex vivo muscle contraction and electrophysiological studies showed a reduced safety factor of neuromuscular transmission in all models. NMJs had ~ 40% smaller miniature endplate potential amplitudes compared with wild type, indicating postsynaptic sensitivity loss for the neurotransmitter acetylcholine. However, nerve stimulation‐evoked endplate potential amplitudes were unchanged. Consequently, quantal content (i.e. the number of acetylcholine quanta released per nerve impulse) was considerably increased. Such a homeostatic compensatory increase in neurotransmitter release is also found at NMJs in myasthenia gravis, where autoantibodies reduce acetylcholine receptors. However, high‐rate nerve stimulation induced exaggerated endplate potential rundown. Study of NMJ morphology showed that fragmentation of acetylcholine receptor clusters occurred in all models, being most severe in mdx/utrn^?/? mice. Overall, we showed mild ‘myasthenia‐like’ neuromuscular synaptic dysfunction in several Duchenne mouse models, which possibly affects muscle weakness and degeneration.     

Measurement in Duchenne muscular dystrophy: considerations in the development of a neuromuscular assessment tool

A review of the measures relating to the monitoring of disease progression in Duchenne muscular dystrophy was undertaken as part of the work of the North Star Clinical Network for Paediatric Neuromuscular Disease Management developing a standardized assessment protocol for ambulant children in the UK. This article outlines the process of identifying possible measures. Detailed consideration has been given to key measures of muscle strength and function. As well as the usual assessment of the validity and reliability of the measures, three key characteristics were identified as necessary to the assessment of scales used in health care: (1) the type of scale used; (2) the clinical significance of the attribute being measured; and (3) the mathematical properties of the data provided. Consideration of such aspects in the early stage of a study facilitates the choice of measures, and the analysis and interpretation of data in the longer term.     

免疫组织化学dystrophin染色诊断Duchenne型肌营养不良症的研究

目的 探讨Duchenne型肌营养不良症(DMD)肌萎缩蛋白(dystrophin)表达规律和临床意义.方法 收集我院7例DMD患者作为试验组,7例非DMD患者为对照组.使用抗dystrophin杆状结构域单抗、免疫组织化学染色,观察肌膜dystrophin表达.结果 7例DMD患者肌细胞膜dystrophin阴性,7例非DMD患者dystrophin染色阳性.结论 证实DMD患者肌细胞膜dystrophin表达阴性,揭示dystrophin缺失是其发病机制,可以作为确诊DMD手段,对临床诊断DMD有实际意义.