儿童线粒体脑肌病伴高乳酸血症和卒中样发作综合征2例报告

目的：探讨线粒体脑肌病伴高乳酸血症和卒中样发作综合征(MELAS)的诊断与治疗。方法回顾性分析2例MELAS患儿的临床特征及诊疗过程。结果2例患儿主要临床表现为卒中样发作、抽搐、视物模糊、高乳酸血症；发作期头颅磁共振成像结果符合典型的MELAS综合征影像学表现；基因测序存在mtDNA的A3243G点突变；改善供能及皮质激素治疗后症状明显改善。结论 MELAS临床症状复杂多样，血乳酸及头颅磁共振成像检查有助临床诊断，确诊需要肌肉活检或基因检测，皮质激素治疗有效。     

双胎兄弟MELAS 综合征的临床特点

目的探讨异卵双胎兄弟同患线粒体脑肌病伴乳酸血症与卒中样发作综合征(MELAS)的临床特点。方法回顾分析1对异卵双胞胎兄弟同患MELAS病例的临床表现、实验室检查、脑电图、影像学、基因检测结果及诊疗过程。结果先证者,男,7岁时以间断头痛、呕吐、抽搐起病,既往运动不耐受、易疲劳,伴有身材矮小、皮肤多毛,空腹血乳酸值增高,多次视频脑电图背景活动慢化,头颅磁共振成像示随病情反复发作病灶具有迁徙、易变,mtDNA A3243G点突变率34.7%,确诊MELAS。同期筛查同胞异卵弟弟A3243G突变率30%,但无临床症状,间隔3年后以抽搐起病。结论早期基因检测并筛查家系有助于MELAS的诊断,A3243G突变率高,起病年龄早,临床症状重。     

儿童线粒体病心脏损害23例临床分析

目的探讨儿童线粒体病心脏损害的临床表现。方法对23例线粒体病患儿临床资料进行回顾性分析,包括询问病史、体格检查、心电图、超声心动图和心肌酶谱、病理检查、分子遗传学检查。结果15例线粒体脑病-乳酸血症-卒中样发作综合征(MELAS综合征)患儿中,9例行心电图检查6例异常;9例行超声心动图检查,1例发现肥厚性心肌病;12例行心肌酶谱检查,6例CK-MB质量升高,1例心肌肌钙蛋白I(cTnI)升高。8例亚急性坏死性脑脊髓病(Leigh综合征)患儿中,5例行心电图检查,4例异常;2例行超声心动图均未发现异常;6例行心肌酶谱检查,3例CK-MB质量增高。13例MELAS综合征患儿行分子遗传学检测,9例发现外周血白细胞线粒体DNA(mtDNA)存在3243位点A→G突变。6例Leigh综合征患儿行分子遗传学检测,2例发现外周血白细胞mtDNA存在8993位点T→C突变。结论线粒体病并心肌损伤常见,且会导致心肌病发生。     

Leigh综合征患儿核基因和线粒体基因突变的初步分析

目的探讨中国人Leigh综合征患儿的发病机制,并对已知的部分核基因和线粒体基因突变进行分析。方法对1992-2006年收集的来自我国28个省、自治区或直辖市的145例Leigh综合征患儿进行病因学分析。在排除SURF1基因和线粒体基因T8993G、T8993C、A8344G、A3243G四个位点突变后,对80例患儿的丙酮酸脱氢酶E1α亚单位基因（PDHA1）进行PCR扩增和测序分析;并在此基础上对9个线粒体DNA突变位点（G13513A、A13084T、T10158C、C11777A、T10191C、T14487C、T12706C、9537insC和T9176G）进行突变筛查。另对23例A3243G线粒体DNA突变阳性的患儿进行SURF1基因的分析。结果80例患儿中仅1例携带PDHA1基因突变,为214位点C〉T转换,导致PDHA1蛋白第27位氨基酸由精氨酸变为半胱氨酸。而64例患儿其他9个线粒体DNA突变位点筛查均为阴性。在23例携带线粒体DNAA3243G突变的患儿中,6例携带SURF1基因G604C杂合性变异。结论由于Leigh综合征病因复杂多样,使突变分析难于获得阳性结果。为缩小突变筛查的范围,明确Leigh综合征患儿的病因,亟待建立适用于临床检测应用的线粒体呼吸链酶学的测定方法。     

以癫痫持续状态起病的线粒体脑肌病伴乳酸血症和卒中样发作患儿临床特点

目的探讨线粒体脑肌病合并乳酸血症与卒中样发作(MELAS)出现癫痫持续状态患儿的临床特点及治疗。方法回顾性分析4例以癫痫持续状态起病并最终确诊为MEILAS患儿的临床、脑电图、影像学及治疗。结果 4例患儿均以癫痫持续状态起病,血清乳酸、血氨、心肌酶升高,血钠降低,伴代谢性酸中毒;发作期及发作间期脑电图均有相应表现;头颅影像学发现基底节钙化、脑萎缩,急性期可见皮层水肿;基因检测提示mtDNA3243位点突变。结论 MELAS的癫痫发作较难控制,应尽早诊断,选择合适的抗癫痫药物及相关对症治疗,以减轻脑损伤。     

儿童MELAS综合征临床及分子遗传学特点分析

目的　探讨线粒体脑病伴乳酸酸中毒和卒中样发作综合征 (MELAS综合征 )临床及分子遗传学特点。方法　对北京大学第一医院儿科 1998～ 2 0 0 3年收治的 8例MELAS综合征患儿临床表现、一般实验室检查、肌肉病理及线粒体DNA32 4 3位点点突变检测结果进行分析。结果　 ( 1)临床特点 :早期智力运动发育里程碑基本正常 ;多数患儿身材矮小伴多毛 ;6例肌肉受累 ;中枢神经系统症状出现年龄 3～ 13岁 ,其中发作性头痛 5例 ,偏瘫、视力障碍、智力倒退各 4例 ,惊厥 7例。 ( 2 )实验室检查 :6例静态乳酸、丙酮酸升高 ;5例行血气分析仅 1例示代谢性酸中毒 ;肌酸肌酶均正常 ;3例行肌电图仅 1例异常 ;7例行肌活检均见异常线粒体堆积 ;脑电图均示背景慢波增多 ;头颅MRI示 5例枕部异常信号 ,5例双基底节异常信号 ;1例脑干及小脑异常信号 ;1例小脑萎缩伴轻度大脑皮层萎缩 ;1例未见异常。 ( 3)分子遗传学 :5例白细胞线粒体DNA存在 32 4 3位点A→G突变 ,突变率为 37%～6 0 % ,其中 1例母亲存在同样突变。结论　MELAS综合征的临床表现多样 ,血乳酸丙酮酸、肌肉病理、头颅MRI及分子遗传学检查对于诊断此病尤为重要     

线粒体细胞病1例临床和基因突变分析

目的分析线粒体细胞病的临床表现、遗传学特点及其基因突变特点,从基因水平了解线粒体细胞病致病因素,并达到基因诊断和遗传咨询的目的。方法对1例线粒体细胞病患儿临床表现及实验室检查结果进行分析。提取患儿外周血基因组DNA,运用聚合酶链式反应先扩增患儿外周血线粒体基因3243、8344、8993三个热点突变所在片段,对扩增片段进行正反向序列测定,以检测突变。然后扩增已知的62个常见突变位点所在片段,对扩增片段同样进行正反向序列测定以检测突变。随机选择55例无血缘关系的健康成年人作为健康对照。结果男性患儿,出生2 d出现持续高乳酸血症、反复严重代谢性酸中毒、黄疸、肝功能异常、抽搐,头颅CT平扫示双侧大脑实质弥散性对称性低密度灶,2个月龄时死亡。线粒体3243、8344、8993三个位点均未发现突变,但细胞色素B基因存在15765 G→A突变,导致氨基酸序列340位由甘氨酸(G)转变为谷氨酸(E)。患儿母亲身体健康,外周血中亦同样存在该突变,患儿父亲及55例健康对照者皆无此突变。结论线粒体细胞病可表现为高乳酸血症、代谢性酸中毒、肝功能异常、神经系统疾病等多脏器功能损伤。线粒体细胞色素B基因15765 G→A突变可能是线粒体细胞病的一个致病突变。     

儿童线粒体脑病的临床和分子遗传学特点及其预后

目的探讨儿童线粒体脑病临床及分子遗传学特点和预后。方法对中国人民解放军总医院儿科2008—2013年收治的儿童线粒体脑病11例患儿临床表现、一般实验室检查、肌肉病理及线粒体基因点检测结果进行分析并随访。结果患儿发病年龄6个月~12岁,病程2个月~3年,其中线粒体脑肌病伴乳酸酸中毒和卒中样发作(MELAS)型6例,其他呼吸链酶缺陷引起的线粒体疾病5例。主要表现为抽搐、呕吐、头痛、智力低下、偏瘫等;10例患儿有乳酸升高,其中7例伴丙酮酸升高;6例脑电图示背景慢波增多;头颅磁共振显示受累部位依次为:双侧基底节2例、颞顶枕叶3例、脑内多发病变2例、额顶枕叶1例、顶枕1例、丘脑中脑1例;其中3例行磁共振血管成像(MRA)检查,2例正常,1例左大脑中后动脉分支较对侧少;磁共振波谱分析(MRS)乳酸高峰者3例。2例患儿行骨骼肌病理检查,1例接受骨骼肌病理检查显示异常线粒体堆积。线粒体呼吸链复合物(I~V)缺陷结果复合物Ⅳ缺陷2例,Ⅴ缺陷1例,联合复合物缺陷Ⅰ+Ⅲ缺陷2例。5例白细胞线粒体DNA发现不同位点突变,分别为T8993G、T8993C突变、A3243G突变和11777突变。结论儿童线粒体脑病临床表现多样,实验室检查、头颅影像、基因突变及呼吸链酶学检查有助于早期诊断和治疗,该病预后不佳。     

线粒体tRNAser(UCN)基因突变致线粒体脑肌病1例并文献复习

目的分析1例线粒体细胞病患儿的临床表现及其基因突变特点。方法对1例临床诊断为线粒体脑肌病患儿归纳总结其临床表现及实验室检查结果，并运用PCR法扩增患儿外周血线粒体基因3243、8344和8993热点突变及已报道的62个常见突变位点所在片段，对扩增片段采用直接测序方法检测突变。在某医院年度体检中选择70名无血缘关系的健康成人作为正常对照，采用PCR RFLP方法进行多态性分析。结果 男性患儿，1岁9个月时出现持续高乳酸血症、反复严重代谢性酸中毒和高氨血症，头颅CT扫描显示双侧额顶叶对称性空泡样低密度灶，考虑线粒体性脑肌病；脑萎缩。2岁时死亡。患儿外周血线粒体基因3243、8344和8993热点突变及已报道的62个常见突变位点均未见突变，患儿线粒体tRNAser(UCN)基因存在7496 T→C突变。为证实在正常人群中线粒体tRNAser(UCN)基因是否存在7496 T→C突变，70名正常对照组皆未发现这一位点突变。结论线粒体脑肌病可以表现为代谢紊乱和神经损伤，应提高警惕。线粒体tRNAser(UCN)基因7496 T→C突变可能导致线粒体细胞病。该突变尚未见报道。     

以脑卒中样发作为主要表现的儿童遗传代谢病

目的提高对遗传代谢性疾病所致儿童卒中样发作的认识。方法采用回顾性方法,对5例确诊为儿童遗传代谢病引发率中样发作患儿的临床表现、生化特点以及诊疗情况进行分析。结果 5例患儿中4男、1女,就诊年龄10～13岁。其中2例高同型半胱氨酸血症患儿起病急,表现为运动障碍和(或)意识障碍,生长发育、智力正常;2例线粒体脑肌病伴乳酸酸中毒和卒中样发作(MELAS)及1例疑似MELAS患儿起病急,病程迁延,以运动障碍、惊厥、视力下降、性格改变为主要表现,体格发育落后于正常同龄儿,病程中出现智力倒退。MELAS患儿血乳酸升高,线粒体基因MELAS A3243G位点突变;高同型半胱氨酸血症患儿血同型半胱氨酸浓度升高。影像学检查,MELAS患儿以后头部灰质损害为主,高同型半胱氨酸血症患儿为多发性腔隙性脑梗塞、双侧基底节区脑梗塞。结论儿童卒中病因繁多,应注意遗传代谢病引发卒中样发作的可能性;对既往体健,突发卒中者应注意高同型半胱氨酸血症的可能;对体格发育落后,头颅MRI以后头部灰质病变为主的卒中样发作,应注意MELAS的可能。     

Infantile encephalopathy associated with the MELAS A3243G mutation.

MELAS syndrome is typically characterized by normal early development and childhood-onset recurrent neurologic deficits (stroke-like episodes), seizures, short stature, lactic acidosis, and ragged red fibers on muscle biopsy specimens. It is usually, but not invariably, associated with the A3243G point mutation in the mitochondrial DNA tRNALeu(UUR) gene. We report 3 unrelated children with the A3243G mutation who presented with severe psychomotor delay in early infancy. One patient's clinical picture was more consistent with Leigh syndrome, with apneic episodes, ataxia, and bilateral striatal lesions on brain magnetic resonance imaging (MRI). The second patient had generalized seizures refractory to treatment and bilateral occipital lesions on brain MRI. The third child had atypical retinal pigmentary changes, seizures, areflexia, and cerebral atrophy on brain MRI. All patients had several atypical features in addition to early onset: absence of an acute or focal neurologic deficit, variable serum and cerebrospinal fluid lactate levels, lack of ragged red fibers in muscle biopsy specimens. The proportion of mutant mtDNA in available tissues was relatively low (range, 5% to 51% in muscle; 4% to 39% in blood). These observations further extend the phenotypic expression of the A3243G "MELAS" mutation. Our findings confirm previous observations that there is poor correlation between abundance of mutant mtDNA in peripheral tissues and neurologic phenotype. This suggests that other factors contribute to the phenotypic expression of this mutation.     

Acute pancreatitis in an infant with lactic acidosis and a mutation at nucleotide 3243 in the mitochondrial DNA tRNALeu[UUR] gene

The A to G point mutation at position 3243 of the mitochondrial DNA tRNA^Leu(UUR)gene is commonly found in patients with the syndrome of mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS). A male patient was referred at 7 months with failure to thrive, developmental delay, microcephaly and hypotonia since age 2 months. He had developed lactic acidosis and increasingly frequent seizures since age 5 months. The patient was admitted at 15 months with pleural and pericardial effusions, which resolved. Three weeks later he developed evidence of pancreatitis with hyperglycemia, sudden profound increase in lactic acidosis and increased serum lipase. He died unexpectedly the next day of cardiorespiratory collapse following an acute gastro-intestinal hemorrhage. Analysis of mitochondrial DNA (mtDNA) in muscle showed heteroplasmy for the mutation MTTL1*MELAS3243G (> 95%). Infants with this mutation commonly present with failure to thrive, significant developmental delay, and hypotonia, while stroke-like episodes occur later in survivors. They usually have lactic acidosis and a high percentage of mutant mtDNA in muscle.     

Early cardiac involvement in children carrying the A3243G mtDNA mutation

The phenotypic spectrum of the mitochondrial A3243G DKA mutation is highly variable, particularly when occuring in childhood. In contrast to the classical presentation in adulthood (MELAS syndrome; mitochondria! myopathy, encephalopathy, lactic acidosis and stroke-like episodes) children show a different pattern of symptoms, often without the typical encephalopathy or psychomotor regression. We present six children carrying the A3243G mtDNA mutation with a heteroplasmy above 50 % in muscle tissue. The age of diagnosis ranged from 2 weeks up to 14.5 years. The clinical presentation was rather non-specific including muscle weakness, developmental delay and epilepsy. In this small pediatric group we detected presymptomatic cardiac involvement in five out of six children already at an early stage of disease. The cardiac pathology included cardiomyopathy and biventricular hypertrophy with rhythm disturbances (for example long QT-syndrome). The observed cardiac changes do not always increase the risk of cardiac deterioration; however, two of our patients died early on. CONCLUSION: We hypothesize that the A3243G mutation might be underdiagnosed, as patients could suffer from an unexplained cardiac death before the diagnosis is made. We advise performing regular repeated ECGs and echocardiography in all children carrying a A3243G mtDNA mutation independently from the presence of cardiac symptoms.     

Mitochondrial DNA abnormalities and autistic spectrum disorders

OBJECTIVES: To further characterize mtDNA defects associated with autistic features, especially the A3243G mtDNA mutation and mtDNA depletion.Study design Five patients with autistic spectrum disorders and family histories of mitochondrial DNA diseases were studied. We performed mtDNA analysis in all patients and magnetic resonance spectroscopy in three. RESULTS: Three patients manifested isolated autistic spectrum features and two had additional neurologic symptoms. Two patients harbored the A3243G mutation. In two others, the A3243G mutation was not found in accessible tissues but was present in tissues from their mothers. The fifth patient had 72% mtDNA depletion in skeletal muscle. CONCLUSIONS: Autistic spectrum disorders with or without additional neurologic features can be early presentations of the A3243G mtDNA mutation and can be a prominent clinical manifestation of mtDNA depletion. Mitochondrial dysfunction should be considered in patients who have autistic features and associated neurologic findings or who have evidence of maternal inheritance.     

Heterogeneous presentation in A3243G mutation in the mitochondrial tRNA(Leu(UUR)) gene.

AIMS: To clarify the phenotype-genotype relation associated with the A3243G mitochondrial DNA mutation. METHODS: Five unrelated probands harbouring the A3243G mutation but presenting different clinical phenotype were analysed. Probands include Leigh syndrome (LS(3243)), mitochondrial myopathy, encephalopathy, lactic acidosis and stroke like episodes (MELAS(3243)), progressive external ophthalmoplegia (PEO(3243)), and mitochondrial diabetes mellitus (MDM(3243)). Extensive clinical, histological, biochemical, and molecular genetic studies were performed on five families. RESULTS: All patients showed ragged red fibres (RRF), and focal cytochrome c oxidase (COX) deficiency except for the patient with MDM(3243). The mutation load was highest in the proband with LS(3243) (>90%), who also presented the highest proportion of RRF (68%) and COX negative fibres (10%), and severe complex I plus IV deficiency. These proportions were lower in the probands with PEO(3243) and with MDM(3243). CONCLUSION: The most severe clinical phenotype, LS(3243), was associated with the highest proportion of the A3243G mutation as well as the most prominent histological and biochemical abnormalities.     

Classical MERRF phenotype associated with mitochondrial tRNA<Superscript>Leu</Superscript> (m.3243A>G) mutation

Myoclonic epilepsy with ragged red fibres (MERRF) and mitochondrial encephalopathy, lactic acidosis and stroke-like episodes (MELAS) are established phenotypes of mitochondrial encephalopathies. Nearly all patients affected by MERRF harbour a mutation in the mitochondrial tRNA^Lys gene. We report a 13-year-old patient who presented with the classical phenotype of MERRF but was found with the typical mutation of MELAS. The patient presented with myoclonic epilepsy beginning at 10 years of age, a muscle biopsy with ragged red fibres and some COX negative fibres and progressive bilateral MRI hyperintensitivities in the basal ganglia constituting MERRF syndrome but lacked clinical characteristics of MELAS. In particular, stroke-like episodes or lactic acidosis were not present. None of the tRNA mutations described in MERRF were found. However, further analyses showed the tRNA^Leu mutation m.3243A>G usually found in MELAS to be responsible for the condition in this patient. This report highlights the broad phenotypic variability of mitochondrial encephalopathies with juvenile onset. It shows that m.3243A>G mutations can cause classical MERRF and emphasises the significance of comprehensive genetic studies if mitochondrial disease is suspected clinically.     

Functional mitochondrial heterogeneity in heteroplasmic cells carrying the mitochondrial DNA mutation associated with the MELAS syndrome (mitochondrial encephalopathy, lactic acidosis, and strokelike episodes)

Most mitochondrial DNA (mtDNA) alterations associated with human disorders are heteroplasmic, i.e. mutant mtDNA molecules coexist with normal ones within the cell. We addressed the possibility of intermitochondrial exchanges through histologic analyses of cybrid clones with increasing proportion of the MELAS (A3243G) mtDNA transfer RNA point mutation. MtDNA-dependent cytochrome c oxidase activity and protein composition as well as mitochondrial membrane potential appeared heterogeneous in individual cells from clonal heteroplasmic cell populations on the basis of confocal and electron microscopy. The number of defective cells increased with increasing mutation load. We conclude that in the presence of a heteroplasmic mtDNA mutation in the cell type that we studied, intermitochondrial molecular exchanges cannot provide an efficient even distribution of the complementing molecules such as wild-type mtDNA, transfer RNA, or protein. Mitochondria in these heteroplasmic cells cannot, therefore, be considered a single functional unit.     

Clinical and laboratory findings in referrals for mitochondrial DNA analysis

BACKGROUND: Increasingly, mutations of mitochondrial DNA (mtDNA) are being considered when investigating the aetiology of neurological diseases in childhood. However, they are often difficult to predict clinically. METHOD: Mitochondrial DNA analysis was carried out on 190 children from 1992 to 1996. Most patients were screened for large scale rearrangements and point mutations at nucleotide positions 3243, 3271, 8344, and 8993. RESULTS: Mutations were found in only 15 patients (7.9%) and were either large scale rearrangements (seven patients) or point mutations at nucleotide position 3243 (eight patients). Other point mutations were screened for depending on the clinical picture. The age of symptom onset was significantly older in children with an mtDNA mutation (mean 7.0 years) compared with children without a mutation (mean 2.8 years). Neither Leigh's syndrome (28 cases) nor severe infantile lactic acidosis (12 cases) was associated with mtDNA mutation. Only three clinical features were significantly associated with an mtDNA mutation: progressive external ophthalmoplegia, myopathy, and pigmentary retinopathy. Family history was valuable: the point mutation at nucleotide 3243 (but not the large scale rearrangements) was associated with maternal inheritance; and consanguinity was not associated with mtDNA mutations. The only investigation that provided specific evidence of an underlying mtDNA mutation was histochemical staining of muscle biopsy specimens. The large scale mutations associated with Kearns-Sayre syndrome and progressive external ophthalmoplegia were found in DNA from muscle only, not leucocyte DNA; whereas point mutations were found in leucocyte DNA. CONCLUSIONS: Even among children seen at a neurogenetic referral centre, mtDNA mutations were very uncommon. Muscle biopsy was the only investigation to provide evidence of mtDNA abnormality.     

Clinical Presentations of Mitochondrial Cardiomyopathies

To determine the clinical manifestations and interfamilial variability of patients diagnosed with a mitochondrial cardiomyopathy, we reviewed the charts of 14 patients with cardiomyopathy out of 59 patients with mitochondrial disorders who attended the mitochondrial disease clinic at Wolfson Medical Center from 1996 to 2001. All patients underwent a metabolic evaluation including blood lactate, pyruvate, carnitine, and amino acids and urine organic acids. Respiratory chain enzymes were assessed in 10 patients. The mitochondrial DNA (mtDNA) was assessed for mutations.The age at presentation ranged between 6 months and 24 years. Six of the patients died, 5 from heart failure. The cardiomyopathy was hypertrophic in 10 and dilated in 4. Conduction and rhythm abnormalities were present in 6. Eleven patients had family members with mitochondrial disorders. All the patients had additional involvement of one or more systems. Seven patients exhibited a deficiency of a respiratory chain enzyme in the muscle. The MELAS mtDNA point mutation (3243) was found in one patient. Blood lactic acid levels were increased in 5. Brain MRI abnormalities were observed in 4.Conclusions Mitochondrial dysfunction frequently affects the heart and may cause both hypertrophic and dilated cardiomyopathy. The cardiomyopathy is usually a part of a multisystem involvement and may rarely be isolated. The course may be stable for many years, but rapid deterioration may occur. Understanding the biochemical and genetic features of these diseases will enable us to comprehend the clinical heterogeneity of these disorders.