Duchenne型肌营养不良症的临床特点和基因分析

目的探讨Duchenne型肌营养不良症(DMD)的临床特点和基因特点,为临床诊断提供依据。方法回顾性分析2015—2019年中山大学附属第六医院遗传代谢实验室基因检测确诊的15例DMD患儿的基因检测结果和临床资料,探讨DMD的临床特征和基因特点。结果 15例患儿发病年龄1个月～12岁,临床表现以小腿腓肠肌假性肥大、Gowers征及走路摇摆(鸭步)为主,AST、ALT、CK、CK-MB及肌红蛋白等肌酶水平均明显升高。通过组合的高通量检测技术等检查DMD基因情况,结果多为缺失突变,共12例(80.0%),其中大片重复缺失突变10例(66.7%),点突变2例(13.3%);错义突变1例(6.6%);插入突变1例(6.6%);无义突变1例(6.6%)。其中7例(46.7%)患儿母亲进行了相关基因检测,4例患儿母亲为该基因突变点携带者。而根据ACMG变异类型,15例患儿中13例(86.7%)为致病突变,2例(13.3%)为疑似致病突变。同时15例病例中有2例暂无相关文献报道过。所有的突变可发生在基因的任何位置,但缺失的热点区域位于基因的中央区外显子45～55区共8例,占缺失突变的53.3%。结论...     

A review of nutrition in Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a recessive X linked genetic disorder characterised by progressive muscle weakness and reduced muscle tone. Affecting only boys, it limits life expectancy to approximately 20 years. A literature review was conducted using MEDLINE and the Cochrane Library, employing the term 'Duchenne muscular dystrophy'. A total of 1491 articles in English were recovered. These papers were searched thematically under the headings: body composition ( n  = 10), energy expenditure ( n  = 10), nutrition ( n  = 6), corticosteroid therapy ( n  = 55) and gene therapy ( n  = 199). Key dietetic practice points were identified relevant to nutritional management. Papers supporting these key themes were assigned a level of evidence and grade of recommendation. There is limited high-quality evidence to guide the nutritional management of boys with DMD. Currently, the majority of evidence is based on expert opinion and clinical expertise. Delayed growth, short stature, muscle wasting and increased fat mass are characteristics of DMD and impact on nutritional status and energy requirements. The early introduction of steroids has altered the natural history of the disease, but can exacerbate weight gain in a population already susceptible to obesity. Prior to commencing steroids, anticipatory guidance for weight management should be provided. Malnutrition is a feature of end stage disease requiring a multidisciplinary approach, such as texture modification and supplemental feeding. Micronutrient requirements are yet to be determined but, as a result of corticosteroid treatment, vitamin D and calcium should be supplemented. Some evidence exists supporting supplementation with creatine monohydrate to improve muscle strength. More research is needed to provide a higher quality of evidence for dietitians working within this area.     

Predictions of energy intake and energy allowance of patients with Duchenne muscular dystrophy and their validity.

Patients with Duchenne muscular dystrophy are so malnourished that energy supplementation is crucial. Their degree of energy deficiency was assessed as difference between their energy intake and their energy allowance, which were deduced from easily measured parameters. A significant, negative relationship was found between the basal metabolic rate (BMR) (Y, %, BMR/standard BMR) and body weight (X, %, body weight/standard body weight) in the patients, from which the formula for the BMR was deduced to be Y = -1.116X + 174.5 (n = 202, r = -0.72, p less than 0.001). Thus, it is possible to estimate the energy allowance for individual patients by a factorial procedure from the presumed BMR and a factor for physical activity. In addition, their energy intake was calculated from a constant protein-energy % (14.6%) in their diet and nitrogen intake which was deduced from a significant positive correlation between their nitrogen intake (Y, mg/kg/day) and their nitrogen excretion in 24 h urine samples (X, mg/kg/day). This correlation conformed to the equation Y = 1.053X + 32.4 (n = 267, r = +0.76, p less than 0.001). The validities of the above predictions for energy intake and allowance were examined by plotting the degree of energy deficiency (% ratio of presumed intake/presumed allowance) against the concentrations of retinal binding protein, prealbumin and transferrin in the serum, because rapid turnover proteins are sensitive to energy deficiency. Significant positive correlations were obtained with both variables, suggesting that these predictions were valid.     

Body composition and energy expenditure after weight loss following bariatric surgery

OBJECTIVES: To assess the effectiveness of biliopancreatic diversion (BPD) in the treatment of morbid obesity and to evaluate how the procedure affects body weight. SUBJECTS: Fourteen morbidly obese subjects studied before and 30 months after BPD and fifteen healthy volunteers matched for age, sex and height (controls). METHODS: Comparison of the following parameters were made in the study groups before surgery and 30 months after BPD and with those of the controls group: fat mass, fat-free mass, non-protein substrate oxidation, basal metabolic rate, plasma glucose, insulin and free fatty acid concentrations. RESULTS: Obese subjects lost 60.38+/-10.71 kg of weight during 18 months following surgery and then remained stable for another 12 months, when this study was performed. Weight loss was substantially due to a loss of fat mass (FM: 60.13+/-13.01 kg before and 19.02+/-8.61 kg after BPD; p<0.001). FM were not statistically different between post-obese subjects and controls; however, post-obese patients retained significantly more fat free mass (FFM) than controls. Subsequently, basal metabolic rates of post-obese subjects were higher than those of the control group (p<0.05). Fasting non-protein respiratory quotient (npRQ) was significantly lower before BPD than 30 months after the surgery (0.798+/-0.04 vs. 0.90+/-0.048, p<0.001), suggesting that, while obese, patients oxidized more lipids than carbohydrates. Moreover, fasting and two-hour plasma glucose and insulin concentrations decreased significantly after BPD to values comparable to those of the control group. CONCLUSION: Weight loss in obese patients after BPD is mainly due to lipid malabsorption, but increased energy expenditure associated with retaining a high FFM in physically active post-obese subjects may also play a role, enabling them to maintain long-term reduced body weights.     

Diagnosis of Duchenne muscular dystrophy: parents'experiences and satisfaction

The purpose of the study was to investigate parents' experiences of diagnosis of Duchenne muscular dystrophy. Data were collected retrospectively by postal questionnaire from the parents of 158 boys diagnosed at different times and locations and, for some, after lengthy periods of uncertainty. Most parents knew nothing about Duchenne before being given the diagnosis. There was considerable variation in parents' experiences but the only independent predictors of parents' satisfaction with how the diagnosis was given were obtaining the information that they wanted and feeling that they had understood and remembered it. What distinguishes Duchenne from, say, Down syndrome is that doctors are having to deliver a death sentence on a child. Our data show that this can be done in a way that is satisfactory to parents. What is required is empathy and sensitivity to parents' informational and emotional needs.     

Parents' perspectives on coping with Duchenne muscular dystrophy

BACKGROUND: The author, who has a grown son with Duchenne Muscular Dystrophy (DMD), has personally experienced a lack of available information for parents about coping with DMD. Therefore, as a longtime personal goal, she developed this study to address that lack of information. METHODS: Fifteen semi-structured interviews were conducted with 23 parents (n = 7 with both parents; n = 1 with two sisters; n = 6 with mothers only; n = 1 with father only). The purpose of the interviews was to examine the strategies parents use to cope when their sons have DMD. The interviews were conducted in 12 states, taped and transcribed. RESULTS: Grounded theory analysis of the interview data indicated the willingness of these parents to share information to empower others like themselves. CONCLUSIONS: Parents want to be heard and valued as experts on DMD by medical and other professionals who interact with their sons. In addition, they want to proactively participate in their sons' lives and to encourage other parents to do the same.     

Family function in families of children with Duchenne muscular dystrophy

This article investigates the relationships of child- and family-related variables with family function in families with children who have Duchenne muscular dystrophy. Child-related variables included level of disability (indicator: Barthel Index) and age at diagnosis. Family-related variables included caregiver health status (indicator: Duke Health Profile), family income and employment, family support (indicator: Family APGAR), family hardiness (indicator: Family Hardiness Index), and family functioning (indicator: Family Assessment Device). Family function displayed a significant correlation with age at diagnosis, but not with disability level. It was also significantly correlated with family hardiness, caregiver health status, and levels of family support, but not with income or employment variables. These findings highlight the need to assist families to cope with the presence of serious illness in their children.     

Estimating body composition in children with Duchenne muscular dystrophy: comparison of bioelectrical impedance analysis and skinfold-thickness measurement

BACKGROUND: Duchenne muscular dystrophy (DMD) is often associated with obesity, which worsens the handicap early in the course of the disease. Nutritional assessment, however, can be difficult and often misleading in DMD. OBJECTIVE: Two methods of estimating body composition in DMD, skinfold-thickness (ST) measurement and bioelectrical impedance analysis (BIA), were compared with a reference method, labeled water dilution (WD). DESIGN: Body composition was estimated by using ST measurements and BIA (50 kHz, 800 mAmp), as well as the WD method (1 mL H2(18)O/kg) in 11 DMD patients with a mean (+/-SD) age of 10.0 +/- 2.5 y. RESULTS: When compared with the WD method, ST measurement significantly (P < 0.01) overestimated fat-free mass (FFM) (mean +/- SD ST: 24.5 +/- 5.9 kg; mean +/- SD WD: 18.2 +/- 2.5 kg), which led to an underestimation of the percentage of fat mass (%FM) (ST: 23.3 +/- 10.4%; WD: 40.1 +/- 17.1%; P < 0.05). In contrast, estimates obtained with BIA (FFM: 21.5 +/- 4.5 kg; %FM: 31.3 +/- 13.9%) did not differ from those obtained with WD. The difference from the reference method was less for BIA (mean: 3.3 kg; 95% CI: 0.8, 4.9 kg) than for ST (6.3 kg; 2.2, 8.6 kg). WD and BIA defined 73% and 55%, respectively, of the children as obese (%FM associated with body mass index cutoffs for obesity), whereas ST measurements defined 9% as obese (P < 0.01). CONCLUSIONS: Body-composition estimates by BIA are closer to those by WD than are those by ST measurement. Early detection of fat accumulation and longitudinal monitoring of nutritional care are 2 relevant applications of BIA to prevent obesity and hence lessen the burden of DMD.     

18 years experience with mechanical ventilation in patients with Duchenne muscular dystrophy

OBJECTIVE: To find out which patients with Duchenne muscular dystrophy are eligible for starting home mechanical ventilation and what the survival rate is. DESIGN: Retrospective. METHOD: In 48 patients with Duchenne muscular dystrophy who were treated with home ventilation from 1987, the results were assessed in the follow-up visit in February 2005. Initially, ventilation was only given through a tracheotomy (TPPV), but after starting up a multidisciplinary neuromuscular consultation, non-invasive ventilation (NIPPV) was offered in an earlier stage of the disease. The following data were derived from the outpatient medical record: indication for ventilation, vital capacity (VC), arterial blood gas values, duration of ventilation up to February 2005, survival and causes of death. RESULTS: 15 patients died. The 5-year survival rate was 75% from the start of mechanical ventilation and 67% (18/27) of the patients were still living at home at the time of the follow-up visit. The most important causes of death were cardiomyopathy (5/15) and tracheal bleeding (3/15). The group of patients who started ventilation before 1995 (n = 17) had a significantly smaller VC than the group (n = 31) who started after the neuromuscular consultation was set up. The PaCO2 during daytime was significantly higher in the group that started ventilation before 1995 compared to the group that started later. CONCLUSION: Home mechanical ventilation can be implemented effectively in patients with Duchenne dystrophy, with a 5-year survival of 75%.     

Genetic epidemiology of Duchenne muscular dystrophy in Japan: classical segregation analysis

Classical segregation analysis was performed on 651 male probands in 597 families with Duchenne muscular dystrophy (DMD) collected from 20 of 25 National Institutions for Muscle Diseases in Japan. The proportion of sporadic cases is compatible with 1/3 expected for an X-linked lethal trait with an equal mutation rate in egg and sperm, the estimated mutation rates being 9.2 X 10(-5) and 10.9 X 10(-5)/gamete/generation, respectively. The incidence and prevalence among males were estimated to be 29.2 X 10(-5) and 6.7 X 10(-5), respectively. These results indicated no difference from the patterns of DMD in Western countries.     

Duchenne型肌营养不良症植入前遗传学诊断研究进展

植入前遗传学诊断是在胚胎着床前确定其遗传物质是否正常 ,从而决定该胚胎能否移植的一门新兴技术 ,该技术已应用于性别、单基因遗传病及染色体遗传病的诊断。目前世界上已有两百多个正常婴儿通过植入前诊断技术诞生 ,该资料回顾了DMD植入前诊断技术的发展 ,并对其技术路线及目前存在的问题及解决方法进行综述。     

反义寡核苷酸治疗Duchenne型肌营养不良的研究进展

Duchenne型肌营养不良(DMD)是由抗肌萎缩蛋白基因Dystrophin发生移码突变导致的儿童遗传性致死性肌病。反义寡核苷酸(AON)靶向外显子中的剪接调控序列可以诱导Dystrophin基因的相应外显子跳读,以恢复dystrophin mRNA阅读框,是目前新的DMD治疗方法。该治疗方法的有效性已在患者来源的肌细胞及动物模型中得到证实。目前,AON靶向治疗DMD已经进入药物临床试验阶段。笔者拟对DMD的分子致病机制、AON治疗DMD的作用机制及其临床试验新进展进行综述,为AON在DMD治疗中的临床应用提供理论依据。