乳酸和丙酮酸最小运动量试验对线粒体肌病的诊断价值

目的研究乳酸和丙酮酸最小运动量试验(METLP)对线粒体肌病的诊断价值。方法对肌肉病理明确诊断为线粒体肌病的21例患者、6例其他肌病患者及14例非肌病患者进行METLP检测,并对其检测结果进行分析。结果线粒体肌病组METLP 18例(85.7%)异常,12例≥2项指标异常,主要为运动后血浆乳酸/运动前丙酮酸(L2/P1)>17;其他肌病组METLP 6例(100%)异常,主要为有氧运动后血浆乳酸浓度(L2)升高,或者经休息其血浆乳酸浓度(L3)不降、甚至升高;非肌病组为3例(21.4%)异常。结论在METLP的各项评价指标中,L2/P1作为线粒体肌病与非肌病的诊断参考指标最为可靠;L3/L2可以作为鉴别线粒体肌病与其他肌病的可靠指标;但线粒体肌病的诊断应结合METLP、临床及病理综合分析。     

线粒体肌病与线粒体脑肌病的酶组织化学和超微结构改变

目的：探讨原发性线粒体肌病与脑肌病的病理特征及临床特点。方法：对11例原发性线粒体肌病与脑肌病患者的临床表现，酶组织化学及超微结构进行分析，结果：11例MGT染色均发现有不整红边纤维（RRF），其中单纯表现为肌无力的患者7例，合并中构神经系统受累者4例，RRF出现比例为6．4％－10．3％，电镜观察11例，9例表现为线粒体数目增多，形态异常，嵴排列紊乱等。均可见线粒体内类结晶状包涵体。2例线粒体改变只见数量增多，未见其他异常。结论：光镜下酶组化染色发现典型RRF，对线粒体肌病与脑肌病的初步论断有重要价值。电镜观察肌膜下线粒体异常增多且形态异常，特别是线粒体内类结晶状包涵体的出现，对本病的确诊有重要意义。     

An abnormal exercise test response revealing a respiratory chain complex III deficiency

A 29-year-old man with a progressive exertional muscle intolerance since childhood was referred for incremental exercise test on a bicycle ergometer. The response pattern suggested a mitochondrial myopathy: that is, a greatly reduced maximum oxygen consumption with appropriate heart rate increase and an anaerobic threshold point reached early. The metabolic investigation in plasma revealed an abnormal oxidoreduction status (hyperlactataemia and high lactate/pyruvate ratio) at rest and after a carbohydrate rich meal. The histochemical examination of a muscle biopsy revealed red granular deposits under the sarcolemma for all type 1 fibers. Oxypolarographic and enzymological studies of the mitochondrial respiratory chain in both isolated mitochondria and muscle homogenate demonstrated a marked deficiency of ubiquinol cytochrome c reductase (complex III) activity.     

Quantification of changes in muscle from individuals with and without mitochondrial disease

Introduction: Muscle biopsy is used in the diagnosis of mitochondrial disorders. There are limited data on the normal ranges, so interpretation of findings can be difficult. Methods: We evaluated the percentage of fibers showing mitochondrial abnormalities using Gomori trichrome staining, succinate dehydrogenase, and cytochrome oxidase histochemistry in autopsy samples taken from 45 individuals without evidence of muscle disease and biopsies from 17 patients with mitochondrial disorders. Results: In controls, mitochondrial abnormalities were rare before the fifth decade, and most had <0.1% abnormal fibers. The proportion of abnormal fibers increased with age and was higher in deltoid than quadriceps. Most patients with mitochondrial disorders had >0.5% abnormal fibers. Conclusions: Although some patients with mitochondrial disease have very few muscle fibers that show mitochondrial abnormalities, a rate of abnormality of >0.5% fibers, in the absence of a primary muscle disease this should raise the possibility of a mitochondrial disorder. Muscle Nerve, 2011     

Skeletal muscle ultrasonography in children with a dysfunction in the oxidative phosphorylation system

OBJECTIVE: The aim of this prospective study was to investigate the diagnostic value of quantitative skeletal muscle ultrasonography in children suspected of having a mitochondrial disorder. METHODS: Muscle thickness and quantitatively determined echo intensity of four muscles were established in 53 children with symptoms indicative of a mitochondrial disorder. RESULTS: A sensitivity of 25 to 46 % was found, depending on the chosen cut-off point (abnormal or borderline abnormal), with a specificity of 85 to 100 %. Except for one, all abnormal ultrasound scans were found in children over five years of age. Within the group of patients with a mitochondrial disorder, a significant correlation was found between muscle echo intensity and age (r = 0.38; p = 0.047). CONCLUSIONS: We conclude that skeletal muscle ultrasound can be of additional value in the diagnosis of children with suspected mitochondrial disorders, especially in children over five years of age. With its low sensitivity, it is not suitable for screening purposes. However, since all abnormal ultrasound scans were found in children with a mitochondrial disorder, and no significant correlation with the MDC score was found, muscle ultrasound can be used complementary to this scoring system to facilitate the decision-making in pursuing further invasive diagnostics.     

Biochemical analysis using biopsied muscle in 72 patients with metabolic myopathies

Biochemical analysis using biopsied muscle specimens was performed on 72 cases who had symptoms suggesting metabolic myopathies. Sixteen out of 72 cases (22%) were diagnosed as having chemically confirmed metabolic defects. Of these 16 cases, 9 had defects in the glycolytic pathway (glycogen storage disease type II; 3 cases, type III; 1 case, type V; 3 cases, phosphoglycerate kinase deficiency; 1 case, phosphoglucomutase deficiency; 1 case) and 7 cases in mitochondrial metabolism (complex IV deficiency; 4 cases, carnitine deficiency; 3 cases). Among 14 cases who were strongly suspected as having a defect in the glycolytic pathway because of abnormal ischemic forearm test, 6 (43%) showed biochemically proved glycolytic defects. These data suggest that care should be taken when evaluating the results of ischemic forearm test. In addition, we should carefully interpret the muscle histochemistry, because histochemical stains including PAS might be fairly normal in the defects with second step glycolytic pathway.     

Skeletal muscle mitochondrial dysfunction in alternating hemiplegia of childhood

Alternating hemiplegia of childhood is an uncommon disease characterized by repeated, transient attacks of hemiplegia. Its pathophysiology is uncertain, but attention recently has focused on possible mitochondrial abnormalities. Using ³¹P magnetic resonance spectroscopy, we studied gastrocnemius muscle in 5 patients with alternating hemiplegia, aged 8 to 30 (mean, 18) years, at rest and during incremental aerobic exercise and recovery. There were no significant differences in resting muscle between patients and a control group aged 7 to 42 (mean, 19) years. Exercise performance was grossly impaired in the patients, the mean duration being 30% of normal. The total change in pH during exercise was somewhat less than in control subjects, while the changes in phosphocreatine concentration and intracellular ADP were similar. Thus the average overall rate of fall of phosphocreatine concentration during exercise was three-fold greater than in control subjects. However, the initial rate of ATP turNovemberer at the start of exercise (a measure of muscle mass and efficiency) was not abnormal. During recovery, both the initial rate of phosphocreatine resynthesis and the calculated mitochondrial capacity were reduced by about 35%. This mitochondrial defect probably explains most of the abnormalities seen during exercise.     

Cytoplasmic body and mitochondrial DNA deletion

A patient with chronic progressive external ophthalmoplegia (CPEO) who had abundant cytoplasmic bodies in muscle fibers and a deletion of mitochondrial DNA is reported. The patient was a 26-year-old male suffering from ophthalmoplegia from age 21. He had a marfanoid skeletal abnormality and perceptive hearing loss, but had neither retinopathy, ataxia, nor dementia. In the mitochondria isolated from the biopsied skeletal muscle, NADH-ubiquinone oxidoreductase activity was slightly decreased, succinate-cytochrome c reductase activity was slightly increased, and cytochrome c oxidase activity remained normal. Southern blot analysis of the muscle DNA identified heteroplasmy composed of a normal-sized mitochondrial DNA and a mutant mitochondrial DNA with a 4.2-kilobase deletion. The PCR plus S1 analysis showed that the deletion extended from nucleotide position 7860 +/- 60 to 12,090 +/- 70. The histological studies of the biopsied muscle revealed ragged-red fibers and cytochrome c oxidase-negative fibers in 15.7% and 18.6% of the muscle fibers, respectively. Other conspicuous histological change was abundant cytoplasmic bodies surrounded by clusters of abnormal mitochondria. The cytoplasmic bodies were found preferentially in type 1 fibers, and exclusively in cytochrome c oxidase-negative fibers and in ragged-red fibers. Focal existence of cytoplasmic bodies in muscle fibers with abnormal mitochondria suggests that segregated distribution of the abnormal mitochondria with deleted mitochondrial DNA is involved in the pathogenesis of cytoplasmic bodies.     

Lipoic (thioctic) acid increases brain energy availability and skeletal muscle performance as shown by in vivo31P-MRS in a patient with mitochondrial cytopathy

A woman affected by chronic progressive external ophthalmoplegia and muscle mitochondrial DNA deletion was studied by phosphorus magnetic resonance spectroscopy (³¹P-MRS) prior to and after 1 and 7 months of treatment with oral lipoic acid. Before treatment a decreased phosphocreatine (PCr) content was found in the occipital lobes, accompanied by normal inorganic phosphate (Pi) level and cytosolic pH. Based on these findings, we found a high cytosolic adenosine diphosphate concentration [ADP] and high relative rate of energy metabolism together with a low phosphorylation potential. Muscle MRS showed an abnormal work-energy cost transfer function and a low rate of PCr recovery during the post-exercise period. All of these findings indicated a deficit of mitochondrial function in both brain and muscle. Treatment with 600 mg lipoic acid daily for 1 month resulted in a 55% increase of brain [PCr], 72% increase of phosphorylation potential, and a decrease of calculated [ADP] and rate of energy metabolism. After 7 months of treatment MRS data and mitochondrial function had improved further. Treatment with lipoate also led to a 64% increase in the initial slope of the work-energy cost transfer function in the working calf muscle and worsened the rate of PCr resynthesis during recovery. The patient reported subjective improvement of general conditions and muscle performance after therapy. Our results indicate that treatment with lipoate caused a relevant increase in levels of energy available in brain and skeletal muscle during exercise.     

Misdiagnosis of mitochondrial myopathies: a study of 12 thymectomized patients

INTRODUCTION: Myasthenia gravis and mitochondrial myopathies have common symptoms (fatigability, ophthalmoplegia) that could lead to diagnosis confusion. METHODS: We systematically reviewed medical history and ancillary investigations regarding 12 patients (7F/5M, mean age 47+/-14 years) having a mitochondrial myopathy but who were previously misdiagnosed as autoimmune myasthenia gravis and in whom a thymectomy was performed. RESULTS: Ocular palsy, ptosis and bulbar palsy were present in all patients. Limb fatigability was present in 9 cases. Symptoms were fluctuant but without remission. The misdiagnosis of myasthenia was based on the following arguments: 1) decremental EMG response (2 cases); 2) positive injectable anticholinesterase drugs test (3 cases); 3) partial response to oral anticholinesterase medications (2 cases); 4) AChR antibodies titer of 0.6 nM considered as positive (1 case). A multisystemic involvement was present in 5 patients: peripheral neuropathy (2 cases), deafness (2 cases), cardiopathy (3 cases), cerebellar involvement (2 cases) and myoclonia (1 case). The diagnosis of mitochondrial myopathy (at a mean age of 38+/-12 years) has been certified on the results of muscle biopsy showing mitochondrial proliferation (12 cases) and deleted mitochondrial DNA (8 cases). CONCLUSIONS: In a patient presenting with oculomotor symptoms and muscle fatigability, progressive course and multisystemic involvement are major arguments for a mitochondrial myopathy. In the absence of relevant criteria arguing for Myasthenia Gravis (significant variability of muscle weakness, positive titer of anti-AChR or anti-MuSK antibodies, decremental EMG response), a muscle biopsy is required before indication of thymectomy to exclude a mitochondrial disease.     

Late-onset hereditary myopathy with abnormal mitochondria and progressive dementia

A family with autosomal dominant late-onset progressive dementia and myopathy is described. Electron microscopy of muscle revealed abnormal mitochondria in the proband. Thus, the disease may be classified as a "mitochondrial encephalomyopathy". The cases are unique because dementia was a dominating feature and because the symptoms developed late in life. These cases may represent a new subgroup of the mitochondrial encephalomyopathies.     

A study of mitochondrial electron transfer chain in myotonic dystrophy

Ragged-red fibers (RRFs) are mainly seen in mitochondrial myopathy and related to biochemical defects in electron transfer chain on some occasions. Recently, some papers reported the occurrence of RRFs in the biopsied muscle of myotonic dystrophy (MyD). To examine whether the mitochondrial function is disturbed in MyD, we have studied the biopsied muscles of 12 cases with MyD (10 males and 2 females averaging 38 years of age) morphologically and mainly biochemically. RRFs, ranging from 2--20% of the muscle fibers, were identified in 5 out of 12 cases. On electron microscopy, these fibers had aggregated abnormally enlarged mitochondria with dene bodies, concentrically whirled membranous cristae and paracrystalline inclusions. Clinically, 4 of 5 cases with RRFs had mild to moderate and only 2 of 7 without RRFs had ophthalmoplegia. Bicycle ergometer exercise test showed abnormal increase of lactate/pyruvate ratio in three cases with RRFs. Histochemically, cytochrome c oxidase (CCO) activity was absent selectively in all of the RRFs. Immunohistochemical staining showed the presence of CCO protein by using monoclonal antibody which was specific to CCO subunit IV. Biochemical study with crude muscle extract of 11 cases of MyD showed decreases in NADH dehydrogenase, NADH CoQ reductase, succinate CoQ reductase (SCR), CCO, carnitine actyl transferase activities in most of cases regardless RRFs. To avoid the influence possibly derived from the various stages of muscle degeneration in the biopsied specimens, we calculated the ratio of the enzyme activities compared with succinate dehydrogenase which was located in the electron transfer chain and did not show any statistical difference regardless of RRFs.(ABSTRACT TRUNCATED AT 250 WORDS)     

Electrophysiologic data on myasthenic syndromes of the Lambert-Eaton type. A series of 23 cases]

The electrophysiological data of 23 adult patients with Lambert-Eaton myasthenic syndrome (LEMS) have been reviewed. Lung carcinoma was disclosed in 17. In six cases with an EMG follow-up ranging between one and 17 years no carcinoma was detected. The results of repetitive nerve stimulation test (RNS) were not statistically different between the 2 groups. Low CMAP ulnar amplitude was present in all patients (mean: 1.7 mV). Decremental response at low rate of stimulation (3 Hz) was present in 17/20 (means: 30%). An abnormal incremental response at high rate of stimulation was present in all cases (mean: 826%). The authors emphasize the interest of a 50 Hz stimulation for 4 s. Increase of the 'F-wave' amplitude was noticed in some cases. Electrophysiological changes suggestive of an associated mild neuropathy were noticed in eight patients but H-reflex was present in 3/3 cases. SFEMG abnormalities were found in 6/6 cases. In one case, stimulated SFEMG showed more blockings and an increased jitter with low rate of stimulation. In one case the electrical pattern of RNS could be misinterpreted as myasthenia gravis in one tested muscle only. The author's results suggest that CMAP amplitude and RNS test could be used to appreciate the short-term improvement of LEMS with treatment and in some cases for the long-term follow-up.     

Abnormal insulin secretion in amyotrophic lateral sclerosis

Plasma glucose and insulin (IRI) values during a 50-g oral glucose tolerance test were measured in patients with amyotrophic lateral sclerosis (ALS). Blood sugar curves were abnormal in 7 out of 18 patients in whom glucose tolerance tests were performed, and mean values of plasma glucose levels at 30, 60 and 120 min after glucose loading in the patients were significantly higher than those in control subjects. All cases with generalized muscle atrophy showed abnormal glucose tolerance except for 2 cases who showed borderline response, while in cases with localized atrophy, all but one borderline case demonstrated normal response. IRI response in patients with ALS was abnormal in 11 out of 14 cases, and the mean value at 30 min after glucose administration in the patients was significantly lower than that in control subjects; it was abnormal even in patients who did not have generalized muscle atrophy and showed normal glucose tolerance. The results suggest that abnormal glucose metabolism in ALS is primarily based on the impairment of pancreatic insulin secretion and that the addition of generalized muscle atrophy to the above factor results in apparently abnormal glucose utilization.     

抗线粒体抗体在线粒体脑肌病伴高乳酸血症和脑卒中样发作综合征患者肌纤维中的免疫组织化学表达

目的 探讨抗线粒体抗体(anti-mitochondrial antibody,AMA)在线粒体腩肌病伴高乳酸血症和脑卒巾样发作(MELAS)综合征患者肌肉组织中的免疫组织化学表达特点及其诊断价值.方法 收集经临床、病理以及基因检测确诊的MELAS综合征患者10例,以2名肌肉病理正常者和3例肌肉活体组织检查发现坏死肌纤维的非线粒体病患者作为对照组,对所有15例肌肉冰冻组织标本行AMA免疫组织化学染色.结果 普通光镜下观察发现MELAS患者骨骼肌AMA免疫组织化学染色可见大量不整棕褐色肌纤维(ragged brown fibers,RBF),其形态类似MGT染色下的不整红边纤维(ragged red fibers,RRF).而对照组未发现RBF.结论 AMA免疫组织化学下的RBF是线粒体异常增生的特异性表现,同MGT染色下的RRF类似,可以作为诊断线粒体病异常线粒体的病理学指标.     

The single-fiber EMG in chronic demyelinating neuropathy

Various parameters of single- fiber electromyography (SFEMG) were studied in 19 patients with electrophysiologically and histologically proven chronic demyelinating neuropathy. The mean duration of disease at the time of testing was four years. Motor nerve conduction in the median nerve was abnormal in all patients, whereas sensory nerve conduction was abnormal in all but one. Needle EMG in the extensor digitorum communis (EDC) muscle showed rare fibrillations and fasciculations and some abnormal motor unit potentials in most of patients. SFEMG in the EDC muscle showed an increased fiber density in seven cases (37%) and minimally abnormal jitter in 14 cases (74%). Single-fiber action potentials were stable, whereas blocking was rare. Fiber density was significantly increased in patients with fibrillation in the conventional needle EMG. Our study showed that the SFEMG is mildly abnormal in many patients with demyelinating neuropathy and that this test is useful in detecting and quantitating axonal degeneration in demyelinating neuropathy.     

Mitochondrial encephalomyopathy showing prominent microvacuolation and necrosis of intestinal smooth muscle cells: a case diagnosed by rectal biopsy

A 40-year-old woman who developed intestinal dysmobility was found, at rectal biopsy, to have marked microvacuolation of mucosal muscle layer cells, which corresponded to increased accumulation of abnormal mitochondria. Skeletal muscle biopsy specimens showed ragged-red fibers, vessels strongly reactive for succinic dehydrogenase, and focal deficiency of cytochrome c oxidase. Autopsy performed at the age of 50 revealed prominent accumulation of abnormal mitochondria in the intestinal smooth muscle cells with a mottled distribution of focal necrosis, multiple small cerebral infarcts with diffuse neuronal loss, and rarefaction of the perivascular white matter. Mitochondrial DNA analysis showed a point mutation at position 3243. This case, showing features of both mitochondrial neurogastrointestinal encephalomyopathy and mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS), indicates that routine intestinal biopsy can detect mitochondrial encephalomyopathy with gastrointestinal involvement. The main intestinal changes were extensive accumulation of abnormal mitochondria in the leiomyocytes and scattered focal necrosis. Received: 13 July 1997 / Revised, accepted: 1 December 1997     

In vivo muscle magnetic resonance spectroscopy in the clinical investigation of mitochondrial disease

We have investigated the sensitivity and specificity of a rapid phosphorus magnetic resonance spectroscopy (MRS) protocol for detecting metabolic abnormalities in vivo in skeletal muscle of patients with mitochondrial disease. We examined 17 patients with mitochondrial myopathies. Sixteen had only mild or minimal myopathic signs and symptoms. Phosphorus magnetic resonance spectra from the resting gastrocnemius muscles showed an abnormal intracellular energy state (marked by an increased intracellular inorganic phosphate concentration) in 14/17. In 3/17, this was associated with a decreased phosphocreatine concentration. We also studied 20 patients with other diseases of muscle (inflammatory myopathies, metabolic myopathies, muscular dystrophies, and myasthenia gravis) that can present with similar clinical features. Spectra showed increased intracellular inorganic phosphate concentrations in 6/20. All of these muscle diseases were associated with evidence of muscle fiber necrosis. Abnormalities in the muscle energy state in these cases may be due to secondary mitochondrial dysfunction. Except for cases of polymyositis and dermatomyositis, these 6 other myopathies could be readily distinguished from the mitochondrial myopathies on the basis of the clinical examination and blood tests. We conclude that phosphorus MRS of resting muscle is practical in a clinical setting and has a useful sensitivity and specificity for mitochondrial myopathies when used in conjunction with standard noninvasive tests.     

Hypokinesia and Rigidity as Clinical Manifestations of Mitochondrial Encephalomyopathy: Report of Three Cases

Three patients are reported with a neurological disorder in which hypokinesia and rigidity were the most prominent clinical signs. On CT scan and MRI, two were found to have bilateral lesions in the striatum, mainly in the putamen, and the third had bilateral lesions in the posterior limb of the internal capsule. Laboratory investigations suggested abnormal pyruvate metabolism in all three cases, which was confirmed to skeletal muscle in two cases. In the third the cause was a NADH dehydrogenase defect. The signs and symptoms, the bilateral striatal lesions in two of the patients, and the abnormal pyruvate metabolism justify a classification of mitochondrial encephalomyopathy, resembling Leigh syndrome. This diagnosis must be considered for infants and children presenting with Parkinsonian signs, and mitochondrial energy metabolism should be investigated.     

Corneal clouding: An infrequent ophthalmic manifestation of mitochondrial disease

Corneal clouding is uncommon in infants and children but when present in this age group, it is often associated with mucopolysaccharidoses or Fabry disease. This report describes the case of an 11-year-old male who demonstrated poor weight gain, short stature, segmental myoclonus, and learning problems from 5 years of age followed by general weakness and extremely poor balance. Corneal clouding was evident as a result of a blurred vision complaint at 9 years of age. Both urine metabolic screening for mucopolysaccharidoses and analysis of lysosomal enzymes displayed negative findings. Clinical conditions worsened, including ptosis, progressive weakness, and positive Gowers' sign. Oral glucose lactate stimulation test was positive, therefore a muscle biopsy was performed at 11 years of age. Light microscopy of muscle biopsy disclosed abundant ragged red fibers; electron microscopy revealed abnormal mitochondria in terms of tubular cristae, concentrated cristae, stacking cristae, and round granular patterns of inclusion bodies in the matrix. Thus mitochondrial disease was diagnosed. We conclude that mitochondrial disease should be added to the list of differential diagnosis of corneal clouding in children, especially in cases with normal urine metabolic screening for mucopolysaccharidoses or when assays of lysosomal enzymes appear normal.