A large-scale deletion of mitochondrial DNA in a case with pure mitochondrial myopathy and neuropathy

Here we report the findings from a male patient with myopathy and neuropathy, who has a large-scale deletion of the mitochondrial genome at nucleotides 6570–14150. In the patient’s history, muscle cramps with intermittent weakness and polyneuropathy with disturbed micturition were the predominant symptoms. Morphological examination of a muscle biopsy sample revealed numerous ragged red fibers and prominent paracrystalline intramitochondrial inclusions. The sural nerve biopsy sample disclosed a chronically progressive neuropathy, predominantly axonal in type with a minor demyelinating component. In previous studies the clinical symptoms mentioned above have been related to point mutations at various positions in the mitochondrial DNA (mtDNA). The present study is the first to describe a large (8 kb) deletion of the mtDNA which had apparently caused myopathy and polyneuropathy without encephalopathy. Received: 27 July 1995 / Revised, accepted: 4 December 1995     

A hereditary case of lipid storage myopathy with carnitine deficiency

Summary A case of lipid storage myopathy with systemic carnitine deficiency is reported. There was lipid storage also in the liver but not in leukocytes or the Schwann cells of peripheral nerves.Carnitine concentration was normal in the father but below normal in the mother's muscle where abnormal accumulations of lipid droplets and mitochondria were present between the myofibrils and beneath the sarcolemmal sheath. Histographic analysis demonstrated type I fiber predominance in the patient and in his parents. Hereditary transmission of the disease through a recessive autosomal mechanism might be admitted in this case.

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Zusammenfassung Es wird ein Fall von Fettspeichermyopathie mit Karnitinmangel beschrieben. Die Fettspeicherung ist auch in der Leber, jedoch nicht in den Leukozyten und in den Schwannschen Zellen der peripheren Nerven nachweisbar. In den letztgenannten sowie im Muskelgewebe kann im Elektronenmikroskop eine Glycogen-Speicherung nachgewiesen werden, möglicherweise als unmittelbare Folge des Karnitinmangels auf dem Glycogen-Stoffwechsel.In der Muskulatur der Mutter des Exploranden kann ebenfalls eine zu niedrige Karnitinkonzentration nachgewiesen werden, wobei ein Überschuß an Fettröpfchen und Mitochondrien zwischen den Myofibrillen und subsarko lemmal sichtbar ist. Histochemisch läßt sich ein Überwiegen der Typ-I-Fasern sowohl beim Patienten wie bei den Eltern nachweisen. Die Autoren vermuten, daß im vorliegenden Fall die Krankheit rezessiv autosomal vererbt worden ist.

     

线粒体肌病和脑肌病患者骨骼肌细胞线粒体DNA缺失分析

目的为了检测线粒体肌病和脑肌病患者的骨骼肌细胞的线粒体ＤＮＡ的缺失情况。方法从６例原发性线粒体肌病和１例脑肌病患者的骨骼肌活检标本中，提取总ＤＮＡ，以线粒体ＤＮＡ全长为探针进行分子杂交。结果发现１例ＭＥＲＲＦ患者有５ｋｂ的线粒体ＤＮＡ基因缺失，另１例线粒体肌病患者有１５ｋｂ的线粒体ＤＮＡ基因缺失，剂量分析表明缺失型线粒体ＤＮＡ分别占总线粒体ＤＮＡ的１９．３％和１０．７％。结论线粒体ＤＮＡ基因缺失是线粒体疾病的重要病因之一     

线粒体肌病和线粒体脑肌病组织化学及电镜的研究

本文报告了2例线粒体肌病、3例线粒体脑肌病(MALES1例、MER-RF2例)。所有病例的速冻连续切片的GT染色均见有RRF。在HE—NADH—TR、ATP酶、PAS、、磷酸化酶及SND染色中均见有RRF样增强纤维。细胞色素C氧化酶染色中有2例的切片出现阴性染色肌纤维、考虑为复合体Ⅳ活性低下,余3例染色正常。电镜下观察到除有大量形态异常的线粒体外,并在这些线粒体内见有结晶状、板层状及同心圆样的包涵体。     

线粒体肌病患者的线粒体功能缺陷起源的研究

目的 研究线粒体肌病患者的线粒体功能缺陷的起源。方法 运用含溴化乙锭的培养液培养食管癌细胞，在体外建立性质稳定，长期存活的无线粒体DNA的细胞系，与线粒体肌病患者及正常对照者的血小板进行细胞融合，测定其融合细胞的线粒体功能。结果 使用含溴化乙锭的培养液培养食管癌细胞12天后，细胞完全脱失线粒体DNA，并可稳定培养传代。此细胞与线粒体肌病患者的血小板所形成的融合细胞的线为闰体功能明显较对照组为低。结论 线粒体肌病患者的线粒体功能缺陷可能主要由线粒体DNA突变引起。     

线粒体肌病与线粒体脑肌病的临床分析

目的探讨神经肌肉系统线粒体病的发病机制、临床与病理特征及诊断。方法对7例确诊为线粒体病患者的临床表现、病理检查、实验室与影像学资料进行了回顾性分析。结果该组患者诊断为线粒体肌病3例,线粒体脑肌病4例;其中2例患者血乳酸水平升高;7例患者肌电图均有异常发现,肌肉活检均有特征性的改变;4例线粒体脑肌病患者头部影像学均有异常改变。结论线粒体病主要累及肌肉及中枢神经系统,诊断要求多种手段结合,以临床和病理表现为主,近年来基因方面的研究及影像学诊断发展迅速,目前对本病主要采取对症治疗。     

线粒体肌病与其它神经肌病破碎红纤维的对比研究

为了探讨破碎红纤维（ＲＲＦｓ）对线粒体肌病的诊断价值，对线粒体肌病、多发性肌炎／皮肌炎（ＰＭ／ＤＭ）和脊髓性肌萎缩（ＳＭＡ）３组病人ＲＲＦｓ的形态特点和出现频率进行了对比研究，同时对３组病人线粒体的超微结构改变进行了对比观察。结果发现总ＲＲＦｓ出现频率线粒体肌病组３．０％～１５．２％，ＰＭ／ＤＭ组５．２％～１１．１％，ＳＭＡ组４．５％～４９％。线粒体肌病组以典型ＲＲＦｓ为主，ＰＭ／ＤＭ组以均匀红染纤维为主，ＳＭＡ组以红边纤维为主。线粒体的超微结构观察发现线粒体肌病组线粒体形态改变、嵴排列异常及嵴内包涵体多见，受累线粒体较多。ＰＭ／ＤＭ组和ＳＭＡ组线粒体主要改变是数量增多，形态变小，而外形改变和嵴排列异常少见。未见嵴内包涵体。本研究结果提示ＲＲＦｓ及出现频率不能作为诊断线粒体肌病的形态学标准，典型ＲＲＦｓ对线粒体肌病的诊断较有价值。电镜观察线粒体超微结构改变的不同特点有助于线粒体肌病的鉴别诊断     

线粒体肌病患者腓肠神经的形态计量学分析

对５例已经肌肉活检病理及生化检测证实的线粒体肌病患者的腓肠神经进行光镜及电镜观察，并用形态计量学方法对其进行分析，结果发现大口径的有髓纤维减少，有髓纤维面数密度减小，有髓纤维轴索直径与纤维外直径之比增大，轴索变性，并可见轴索和雪旺细胞浆中有增多的异常线粒体。     

Multiple sclerosis and mitochondrial myopathy: An unusual combination of diseases

A woman with definite multiple sclerosis (MS) and mitochondrial myopathy is described. There were widespread white matter lesions on magnetic resonance imaging (MRI), cerebrospinal fluid (CSF) abnormalities and evoked response changes. Muscle biopsy showed ragged red fibres (RRFs) and cytochrome c oxidase (CoX) deficiency. Southern blot analysis revealed a large deletion of mitochondrial DNA (mtDNA). The patient may be affected by two unrelated diseases, MS and mitochondrial myopathy, but this combination has never previously been reported.     

二氧化锗诱导的线粒体肌病动物模型的发病机制的研究

目的建立线粒体肌病的动物模型，以探讨线粒体肌病的发病机制。方法利用二氧化锗喂养Ｗｉｓｔａｒ大鼠２４周，进行肌肉病理检查，测定生化功能及线粒体ＤＮＡ含量。结果线粒体肌病动物模型被建立，其细胞内自由基含量增多，线粒体ＤＮＡ拷贝数明显减少。结论可能有部分线粒体肌病由环境毒素引起，细胞内自由基含量增多是其重要的发病环节     

Lactate metabolism during exercise in patients with mitochondrial myopathy

Patients with mitochondrial DNA mutations often have elevated plasma lactate at rest and during exercise, but it is unknown whether the high lactate levels are caused by a high production, an impaired oxidation or a combination. We studied lactate kinetics in 10 patients with mtDNA mutations and 10 matched healthy control subjects at rest and during cycle exercise with a combination of femoral arterio-venous differences of lactate, and lactate tracer dilution methodology. During exercise, lactate concentration and production rates were several-fold higher in patients, but despite mitochondrial dysfunction, lactate was oxidized in muscle to the same extent as in healthy control subjects. This surprisingly high ability to burn lactate in working muscle with defective mitochondria, probably relates to the variability of oxidative capacity among muscle fibers. The data suggests that lactate is not solely an indicator of impaired oxidative capacity, but an important fuel for oxidative metabolism, even in muscle with severely impaired mitochondrial function.     

Late-onset mitochondrial myopathy with dystrophic changes due to a G7497A mutation in the mitochondrial tRNASer (UCN) gene

Mutations of mitochondrial tRNA genes are usually associated with multi-systemic disorders with onset of symptoms in childhood or early adulthood. Dystrophic myopathic changes are not typical features of these disorders. We report two siblings with a severe progressive myopathy of late onset without external ophthalmoplegia and without involvement of the central and peripheral nervous system. Muscle biopsy specimens showed severe myopathic changes similar to those found in muscular dystrophies. Molecular analysis revealed a G7497A mutation in the mitochondrial tRNA^Ser(UCN) gene. In both patients, the proportion of mutated mitochondrial DNA in muscle was more than 97%. Mitochondrial disorder associated with the G7497A mutation has to be included into the differential diagnosis of severe progressive late-onset myopathy with histopathological dystrophic myopathic changes. Mitochondrial myopathy and high level of mutated mtDNA might be a characteristic of the G7497A tRNA^Ser(UCN) mutation.     

原发性线粒体肌病与脑肌病(附53例报告)

本文报道了原发性线粒体肌病与脑肌病53例,均经肌活检组织化学染色,超微结构检查及生化检测线粒体呼吸链酶复合体Ⅰ—Ⅳ的活性证实。临床类型包括线粒体肌病44例,KSS及CPEO8例,MELAS型1例。实验室检查包括神经电生理,血清肌酶谱,血乳酸、丙酮酸最小运动量试验.肌活检形态学和生化检测,以及线粒体形态计量分析。并对本组疾病的临床特点,各种检查的诊断价值及治疗进行了讨论。     

Multiple mitochondrial DNA deletions in hereditary inclusion body myopathy

We have recently described an autosomal dominant hereditary inclusion body myopathy (h-IBM). Clinically it is is characterized by congenital joint contractures and slowly progressive, proximal muscle weakness and ophthalmoplegia. There is deterioration of muscle function between 30 and 50 years of age. While young patients show minor pathological changes in muscle, the middle-aged and old patients show rimmed vacuoles and inclusions of filaments measuring 15–18 nm in diameter. Except for the absence of significant inflammation the histopathology is similar to that found in sporadic inclusion body myositis (s-IBM). In s-IBM mitochondrial alterations including cytochrome c oxidase (COX) -deficient muscle fibers are common. These are due to multiple mitochondrial DNA (mtDNA) deletions. In this study we investigated the occurrence of mitochondrial alterations in autosomal dominant h-IBM. Young affected individuals showed no mitochondrial changes but three patients aged 38, 51 and 59 years, respectively, showed ragged red fibers and COX-deficient muscle fibers. Polymerase chain reaction analysis showed multiple mtDNA deletions. By in situ hybridization clonal expansions of mtDNA with deletions were demonstrated in COX-deficient muscle fibers. Most of the analyzed deletion breakpoints showed nucleotide repeats flanking the deletions. The results show that COX-deficient muscle fibers and somatic mtDNA deletions are present in this family with h-IBM. The same factors may be involved in the development of mtDNA deletions in s-IBM and this family with h-IBM. Received: 13 July 1999 / Revised: 6 October 1999 · Accepted: 12 October 1999     

Nemaline myopathy in a newborn infant: a rare muscle disorder

Nemaline myopathy (NM) is a genetically and clinically heterogeneous muscle disorder, defined by the presence of characteristic nemaline bodies on muscle biopsy. The disease has a wide spectrum of phenotypes, ranging from forms with neonatal onset and fatal outcome to asymptomatic forms. The neonatal form is severe and usually fatal. The clinical variability, with differing age of onset and severity of symptoms makes the diagnosis difficult during infancy. There is no curative treatment. L-tyrosine may prevent aspiration by reducing pharyngeal secretions and drooling. Most of the patients die from respiratory and cardiac failure.This article discusses a newborn infant who presented with generalized weakness and respiratory failure. Partial response to L-tyrosine treatment was noted. The case is worth presenting to remind clinicians of congenital myopathies in the differential diagnosis of floppy infant during neonatal period and to emphasize the importance of muscle biopsy in diagnosis.     

Oculopharyngeal somatic myopathy in a patient with a novel large-scale 3,399 bp deletion and a homoplasmic T5814C transition of the mitochondrial DNA

We report a 65-year-old woman with a sporadic form of progressive oculopharyngeal somatic myopathy due to a novel large-scale 3,399 base pair (bp) deletion of the mitochondrial DNA (mtDNA) and co-occurrence of a homoplasmic T5814C transition. The onset of myopathy began from chronic progressive external ophthalmoplegia (CPEO) at age of 20 years. Bulbar weakness, neck and proximal limb paralysis, slowly progressed to eventual respiratory failure. The plasma levels of pyruvate (1.5 mg/dL) and lactate (20.2 mg/dL) were elevated. Muscle biopsy showed decreased enzymatic activity of cytochrome c oxidase, but no ragged-red fibers. Electron microscopy showed "parking-lot" paracrystalline inclusions in the enlarged mitochondria suggestive for mitochondrial myopathy. Sequencing of the whole mitochondrial genome of the patient's muscle and leukocytes showed 3,399 bp deletion of the mtDNA from nucleotide position 8,024 to 11,423 and a homoplasmic thymidine to cytosine transition at nucleotide position 5,814 of the tRNA(Cys) gene of mtDNA (T5814C). T5814C was absent in the white blood cells of the patient's daughter and in 205 normal controls. We conclude that a large-scale deletion may coexist with T5814C transition in patients with sporadic form of mitochondrial cytopathy manifested by slowly progressive oculopharyngeal somatic myopathy.     

Mutations in mtDNA-encoded cytochrome c oxidase subunit genes causing isolated myopathy or severe encephalomyopathy

We report on clinical, histological and genetic findings in two patients carrying novel heteroplasmic mutations in the mitochondrial cytochrome c oxidase subunit genes COII and COIII. The first patient, a 35 year-old man had a multisystemic disease, with clinical symptoms of bilateral cataract, sensori-neural hearing loss, myopathy, ataxia, cardiac arrhythmia, depression and short stature and carried a 7970 G>T (E129X) nonsense mutation in COII. A sudden episode of metabolic encephalopathy caused by extremely high blood lactate lead to coma. The second patient developed exercise intolerance and rhabdomyolysis at age 22 years. A heteroplasmic missense mutation 9789 T>C (S195P) was found in skeletal muscle, but not in blood and myoblasts pointing to a sporadic mutation. Our report of two patients with isolated COX deficiency and new mutations in COX subunit genes may help to draw more attention to this type of mtDNA defects and provide new aspects for counselling affected families.     

Subacute myopathy in a mature patient due to multiple acyl-coenzyme A dehydrogenase deficiency

Introduction: Multiple acyl‐coenzyme A dehydrogenase deficiency (MADD), also called glutaric aciduria type II, is an inherited metabolic disorder resulting from a deficiency in electron transfer flavoprotein (ETF) or of its ubiquinone oxidoreductase (ETF‐QO). It usually occurs in the neonatal period or in early infancy and, very rarely, in adolescents and young adult patients. Methods: We report the case of a 55‐year‐old woman who developed a painful subacute myopathy. Results: Lipid accumulation was found at biopsy. MADD was confirmed by plasma acylcarnitine profile and by assessment of ETF‐QO activity in muscle. Conclusions: This study demonstrates that metabolic myopathies usually found in infancy may be also diagnosed in older patients. MADD may be easily treated by riboflavin and coenzyme Q10 and therefore should be included in the differential diagnosis of adult‐onset painful myopathy. Muscle Nerve 43: 444–446, 2011     

Hereditary protein C deficiency associated with riboflavin-responsive lipid storage myopathy

We report a 14 year old patient who presented lung emboli and deep vein thrombosis in relationship to protein C deficiency. He had a carnitine-deficient lipid myopathy. Fresh muscle homogenate showed low activities in oxidizing [1-¹⁴C]-butyrate, [1-¹⁴C]-octonoate and [1-¹⁴C]-palmitate. A deficient short chain butyryl-CoA dehydrogenase (SCAD) was found in isolated muscle mitochondria. The patient improved dramatically with daily therapy of 200 mg riboflavin, 2 g carnitine and anticoagulation with Coumadin. The treatment was found to restore fatty acid oxidation in fresh muscle homogenate, deficient acylCoA-dehydrogenases in mitochondria and decrease lipid droplets. These results suggest that in this type of lipid myopathy riboflavin supplementation may be effective. The link with protein C deficiency is discussed.