原发性肉碱缺乏致脂质沉积性肌病的临床与病理特点

目的 分析原发性肉碱缺乏致脂质沉积性肌病（LSM）的临床与病理特点。方法 回顾性分析4例可能LSM患者的临床资料。结果 本组患者为亚急性或慢性起病，主要表现为近端肌无力，疲劳不能耐受；血清肌酶有不同程度的升高；肌电图示肌源性损害；病理检查示肌纤维内可见大量细小空泡和裂隙形成；MGT染色无破碎红纤维，油红O染色显示空泡为大量脂滴充填；受累纤维以Ⅰ型纤维为主。电镜证实肌纤维内脂滴堆积，可伴有线粒体的轻度增多。改善能量和糖皮质激素治疗有效。结论原发性肉碱缺乏致LSM是一种以易疲劳和肌无力为主要临床表现的脂质代谢障碍性肌病，病理改变以肌纤维内脂滴堆积为主，一般不伴有线粒体结构的明显异常。糖皮质激素治疗可获得良好疗效。     

Muscle carnitine deficiency and lipid storage myopathy in patients with mitochondrial myopathy

Abnormal carnitine distribution in muscle was found in 22 of 77 patients (29%), with mitochondrial myopathy. Furthermore, total (TC) and free (FC) carnitine levels in muscle were lower in patients than in controls (P < 0.01). Muscle long-chain acylcarnitines (LCAC) were significantly increased in these patients (P < 0.01). Muscle carnitine deficiency was found in 31.5% of patients with lipid storage myopathy (LSM) and in 25.6% of patients with ragged-red fibers (RRF). Therefore, carnitine deficiency can be found in patients with mitochondrial myopathy even in the absence of LSM. Muscle levels of TC and FC were lower in patients with respiratory chain defects than in those with normal respiratory chain (P < 0.01). In contrast, LCAC levels were significantly increased (P < 0.05). Carnitine levels did not differ significantly, among patients with different respiratory-chain defects. Consequently, these patients, owing to their biochemical block, reduce progressively the muscle carnitine pool and subsequent LCAC rise, due to long-chain fatty acid (LCFA) accumulation.     

Muscle carnitine deficiency in old age: Case report and therapeutic results

A muscle carnitine deficiency was discovered in a 67-year-old retired factory worker with a clinical picture of late-onset myopathy. The diagnosis was made by muscle biopsy and free carnitine assay.

Therapy including a medium chain triglycerides diet and 6 g/day of D, L-carnitine per os produced a remarkable clinical improvement confirmed by a control muscle biopsy 15 months later.

Our patient is the oldest one described with muscle carnitine deficiency. The differential diagnosis of a late-onset myopathy should include lipid myopathies, some of which can be treated successfully.     

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.

     

Analysis of organic acids,amino acids,and carnitine in dogs with lipid storage myopathy

Abnormal accumulations of lipid droplets, localized predominantly in histochemical type 1 fibers, were observed in fresh frozen sections of muscle biopsies from 25 dogs with myalgia, weakness, and muscle atrophy. Compared to controls, lactic acidemia, hyperalaninemia, lactic and pyruvic aciduria, variably increased urinary excretion of carnitine esters, and muscle carnitine deficiency were present. These findings support a metabolic block in oxidative metabolism resulting in lactic acidemia in dogs with lipid storage myopathy. © 1998 John Wiley & Sons, Inc. Muscle Nerve 21:1202–1205, 1998.     

Primary carnitine deficiency: adult onset lipid storage myopathy with a mild clinical course

We studied two adult patients with myalgia and muscular fatigability during prolonged physical exercise. Serum creatine kinase was increased and muscle biopsy revealed a lipid storage myopathy affecting predominantly the type I fibres. Skeletal muscle carnitine content was reduced to 15% and 21% of the normal mean values, while serum carnitine levels were either normal or decreased. Four months of oral therapy with L-carnitine (3 g per day) resolved the clinical symptoms completely in both patients, and a subsequent muscle biopsy confirmed a marked reduction of lipid storage, along with increased muscle carnitine levels. The analysis of renal carnitine excretion and the exclusion of possible secondary carnitine deficiencies in both patients are compatible with mild defects of the carnitine transporter in one patient and of carnitine biosynthesis in the other. Since myalgia and muscular fatigue are frequent but unspecified complaints of otherwise clinically unremarkable adult patients, it is important to identify myopathies associated with primary carnitine deficiency because they may be amenable to treatment.     

Familial combined deficiency of muscle carnitine and carnitine palmityl transferase (CPT)

ABSTRACT— Two patients, brother and sister, aged 19 and 16, with combined, partial deficiency of carnitine palmityltransferase (CPT) are reported. Both patients had recurrent exercise-related myoglobinuria. The brother had also experienced an episode of transient renal failure associated with myoglobinuria. Both had elevated CK and myoglobin in plasma between attacks. There was a normal production of lactate in ischaemic forearm exercise, but elevated levels of NH₃, resulting in an increased NH₃/Iactate ratio; 48-h fasting caused no significant changes in cholesterol, triglycerides or glucose, no rise of CK, and a normal ketogenic response, indicating no hepatic enzyme deficiency. Muscle biopsy showed slight changes of myopathy in both patients, with scattered atrophic fibres, but no lipid accumulation or other specific changes, Biochemical analysis of muscle tissue revealed a reduction of carnitine to 48% and 40% and a reduction of CPT to 55% and 59% of normal values, which is similar to the findings in the only previous report of combined partial carnitine and CPT deficiency. The heterogenity of the laboratory findings in CPT deficiencies and the value of the various diagnostic procedures in metabolic myopathies are discussed.     

Multiple mitochondrial DNA deletions in a patient with mitochondrial myopathy and cardiomyopathy but no ophthalmoplegia

Deletions of muscle mitochondrial DNA are known in mitochondrial myopathy patients who have chronic progressive external ophthalmoplegia (CPEO). A 41-year-old patient with no apparent family history of this condition suffers from hypertrophic cardiomyopathy, slight muscle atrophy, and weakness of the extremities, but not from CPEO. A muscle biopsy showed the presence of ragged-red fibers, and Southern blot analysis disclosed multiple deletions of muscle mitochondrial DNA. This combination of clinical features in our patient is atypical in mitochondrial myopathy with demonstrable deleted muscle mitochondrial DNA. Pleomorphic clinical expression is suggested. © John Wiley & Sons, Inc.     

Mitochondrial abnormalities in selenium-deficient myopathy

We report a man who developed selenium-deficient myopathy during long-term parenteral nutrition. Muscle biopsy showed marked mitochondrial depletion in the deep sarcoplasm and enlarged mitochondria at the periphery mainly in type 2 fibers. Muscle weakness improved gradually after the second course of selenium supplementation. The peculiar mitochondrial abnormalities in muscle fibers appear to play a key role in the pathogenesis of selenium-deficient myopathy. © 1998 John Wiley & Sons, Inc. Muscle Nerve 21:637–639, 1998.     

CPEO and carnitine deficiency overlapping in MELAS syndrome

Mitochondrial myopathy, encephalopathy with lactic acidosis and stroke-like episodes (MELAS) syndrome is one of the mitochondrial encephalomyopathies that has distinct clinical features including stroke-like episodes with migraine-like headache, nausea, vomiting, encephalopathy and lactic acidosis. We report a 27-year-old woman who presented with partial seizure, stroke-like episodes including hemiparesis, hemianopia and hemihypethesia, sensorineural hearing loss, migraine-like headache, and lactic acidosis. Brain computed tomographic scan showed encephalomalacia in the right parieto-occipital area and recent hypodensity in the left temporoparieto-occipital area with cortical atrophy. Muscle biopsy revealed ragged-red fibers and paracrystaline inclusions in the mitochondria. Genetic study revealed an A to G point mutation at nucleotide position (np) 3243 of mitochondrial DNA. External ophthalmoplegia and ptosis were also found during two exaggerated episodes in this patient. Therefore, the overlapping syndrome of chronic progressive external ophthalmoplegia in the MELAS syndrome is considered in this case. Furthermore, we also found carnitine deficiency in this patient and she was responsive well to steroid therapy. Muscle biopsy also revealed excessive lipid droplets deposits. Therefore, the carnitine defiency may occur in MELAS syndrome with the A to G point mutation at np 3243. We recommend the steroid or carnitine supplement therapy be applied to the MELAS syndrome with carnitine deficiency.     

Muscle carnitine in hypo- and hyperthyroidism

Weakness is common in both hyper- and hypothyroidism, and skeletal muscle L-carnitine may play a role in this regard, as suggested by studies indicating abnormal levels of carnitine in serum and urine of patients with thyroid dysfunction. Skeletal muscle samples were obtained for carnitine analysis from control subjects, and from hyperthyroid and hypothyroid patients before and after treatment. There was a significant reduction in carnitine, especially the esterified portion, in hyperthyroid individuals, with a return to normal as euthyroid status was regained. In hypothyroid patients, there was a trend for carnitine to be lower than normal and for improvement once euthyroid status was attained. Our data indicate that muscle carnitine levels are affected by both hypo- and hyperthyroidism. A decrease in muscle carnitine in both conditions may contribute to thyroid myopathy.     

Acute mitochondrial myopathy with respiratory insufficiency and motor axonal polyneuropathy

Background: Mitochondrial myopathies (MMs) are mainly presented with chronic muscle weakness and accompanied with other syndromes. MM with acute respiratory insufficiency is rare. Aims: To reveal the clinical, pathological and molecular characteristics of a life-threatening MM. Methods: Muscle biopsy and enzyme staining were performed in skeletal muscles. Mitochondrial DNA (mtDNA) sequencing was analyzed and heteroplasmy were quantified by pyrosequencing. Results: All three patients had tachycardia, acute lactic acidosis, dyspnea and sudden severe muscle weakness. Two patients had calf edema and abdominal pain, and one had a heart attack. Electromyography in two patients showed dramatically decreased axonal amplitudes of motor nerves. Muscle biopsies showed ragged red fibers and dramatic mitochondrial abnormality. A mtDNA m.3243A>G mutation was identified in Patient 1 (mutation load: 29% in blood and 73% in muscle) and Patient 3 (79% in blood and 89% in muscle). A mtDNA m.8344A>G mutation was found in Patient 2 (mutation load 80.4% in blood). Conclusion: MM characterized by lactic acidosis, respiratory failure and acute motor axonal neuropathy is life threatening.     

Short‐ and long‐term effects of endurance training in patients with mitochondrial myopathy

Background and purpose: It is unknown whether prolonged training is a safe treatment to alleviate exercise intolerance in patients with mitochondrial DNA (mtDNA) mutations. Methods: The effect of 3 and 12 months training and 3–12 months deconditioning was studied in four patients carrying different mtDNA mutations. Results: Three‐month moderate‐intensity training increased oxidative capacity by 23%, which was sustained after 6–12 months of low‐intensity training. Training and deconditioning did not induce adverse effects on clinical symptoms, muscle morphology and mtDNA mutation load in muscle. Conclusion: Long‐term training effectively improves exercise capacity in patients with mitochondrial myopathy, and appears to be safe.     

高效液相色谱法检测血浆左旋肉碱方法的建立

目的:建立测定血浆左旋肉碱的高效液相色谱方法。方法:采用KromasilSil色谱柱(150mm×4.6mm,5μm),Agilent1100系列高效液相色谱系统,用衍生化的方法处理血样,绘制标准曲线,并对80名正常人及12例脂肪累积性肌肉病(LSM)患者进行血浆左旋肉碱检测。结果:本方法的回归方程为Y=0.9908C 0.6292,r=0.9999。精密度RSD<4%、加样回收率>70%。稳定性良好。正常男性血浆肉碱平均(50±9.4)μmol·L-1,女性(38±7.6)μmol·L-1。结论:本方法灵敏、准确,适用于临床血浆左旋肉碱浓度的监测。     

Benign mitochondrial myopathy with decreased succinate cytochrome C reductase activity

In most of the cases previously described, the defect on complex II was suggested by low activity of succinate cytochrome C reductase (SCCR). The clinical pattern of the previous 10 cases is heterogeneous and may be limited to one particular tissue or be of a more general nature. We report a 22-year-old-woman, daughter of consanguineous parents, with generalized muscle weakness, easy fatigability and benign course, who showed a decrease of SCCR activity in mitochondria of muscle fibers. Free carnitine (FC) concentration was decreased in muscle as well. The muscle biopsy showed a mild variation in fiber size, with fiber type I predominance, subsarcolemmal oxidative DPNH accumulations, excess of neutral lipids and abnormally large mitochondria with paracrystalline inclusions. A possible inheritance pattern is discussed. Coenzyme Q10 therapy in this patient induced a significant increase of global MRC index score and a decrease of the turns-mean amplitude ratio in the automatic analysis of the EMG.     

肢带型线粒体肌病一个家系的临床和病理特点研究

目的研究肢带型线粒体肌病一个家系中患者的临床和骨骼肌病理特点。方法对一组以进行性肌肉无力为主要特点的家系中的3名患者进行临床资料收集及肌肉活检病理分析,对家系成员行线粒体基因检测。结果该家系患者发病年龄为30~47岁,主要表现为躯干肌及四肢近端肌无力和运动耐力下降,晚期出现呼吸肌受累。血肌酸激酶水平轻度升高,血乳酸升高,电生理检查结果示肌源性损害。骨骼肌病理检查显示3名患者均存在典型的破碎红纤维(RRF),且患者病程越长(分别为2年、4年和14年),肌无力严重程度越重,RRF数量越多(分别为5%、10%和30%)。细胞色素c氧化酶(COX)染色中RRF以深染为主,也可见阴性的RRF。琥珀酸脱氢酶(SDH)染色均未发现琥珀酸脱氢酶高反应性血管(SSVs)。基因检测发现该家系存在mt DNA A3243G突变。结论肢带型线粒体肌病患者选择性累及躯干和四肢近端肌群,骨骼肌中的RRF数量与患者病情进展程度呈正相关。     

Respiratory insufficiency in desminopathy patients caused by introduction of proline residues in desmin c-terminal alpha-helical segment

Mutations in desmin gene have been identified in patients with cardiac and skeletal myopathy characterized by intracytoplasmic accumulation of desmin-reactive deposits and electron-dense granular aggregates. We characterized two new desminopathy families with unusual features of adult-onset, slowly progressive, diffuse skeletal myopathy and respiratory insufficiency. Progressive reduction of respiratory muscle strength became clinically detectable between the 3rd and the 8th years of illness and led to recurrent chest infections and death in one of the patients. Novel mutations, A357P and L370P, predicted to introduce proline residue into a highly conserved alpha-helical region of desmin, were identified. Proline is known to disrupt the alpha-helix. In addition, the A357P mutation distorts a unique stutter sequence that is considered to be critically important for proper filament assembly. Functional assessment in two cell-lines, one of which does and the other of which does not constitutively produce type III intermediate filaments, demonstrated the inability of mutant desmin carrying either the A357P or the L370P mutation to polymerize and form an intracellular filamentous network. The results of this study indicate that respiratory insufficiency is an intrinsic feature of disease associated with specific desmin mutations; in some patients, respiratory weakness may present as a dominant clinical manifestation and a major cause of disability and death.     

Biochemical and genetic studies in a family with mitochondrial myopathy

We present a family with severe exercise intolerance, progressive proximal weakness, and lactic acidemia. Fifteen of 24 family members in five generations were affected. Since the affected males do not have offspring at this time, the family pedigree is consistent with either maternal or autosomal dominant inheritance. Muscle histochemistry showed ragged-red fibers and electron microscopy showed globular mitochondrial inclusions. Biochemical analysis showed reduced muscle activities of mitochondrial NADH-cytochrome c reductase (1 of 2 patients), succinate-cytochrome c reductase (2 patients), and cytochrome c oxidase (2 patients). For 1 patient, sequence analysis of 44% of the muscle mitochondrial DNA including all 22 transfer RNA regions showed no point mutation with pathogenic significance. Southern blot analysis showed no deletion. Six affected members of the family were treated with methylprednisolone (0.25 mg/kg) for 3 months. Muscle strength, serum lactate, and energy metabolism at rest (measured by ³¹P magnetic resonance spectroscopy) significantly improved with treatment. © 1997 John Wiley & Sons, Inc. Muscle Nerve 20: 1219–1224, 1997     

A series of West European patients with severe cardiac and skeletal myopathy associated with a de novo R406W mutation in desmin

Abstract. Desminopathy is a familial or sporadic cardiac and skeletal muscular dystrophy associated with mutations in desmin. We have previously characterized a de novo desmin R406W mutation in a patient of European origin with early onset muscle weakness in the lower extremities and atrioventricular conduction block requiring a permanent pacemaker. The disease relentlessly progressed resulting in severe incapacity within 5 years after onset. We have now identified three other patients with early onset rapidly progressive cardiac and skeletal myopathy caused by this same desmin R406W mutation. The mutation was present in each studied patient, but not in their parents or other unaffected family members, indicating that the mutation in all four cases was generated de novo. The patients mutationcarrying chromosomes showed no similarity, suggesting that the R406W mutation has occurred independently. These observations strongly confirm that the de novo R406W desmin mutation is the genetic basis for early-onset cardiac and skeletal myopathy in patients with sporadic disease and indicate that desmin position 406 is a hot spot for spontaneous mutations. The high pathogenic potential of this mutation can be explained by its location in the highly conserved YRKLLEGEE motif at the C-terminal end of the 2B helix that has a critical role in the process of desmin filament assembly.     

Novel mutation in MYH7 gene associated with distal myopathy and cardiomyopathy

A 25-year-old woman had childhood-onset muscle weakness and dilated cardiomyopathy. She exhibited predominantly distal weakness with early toe walking. Dilated cardiomyopathy required cardiac transplantation at age 15 years. We identified a de-novo, heterozygous, missense mutation, c.2348G>C (p. Arg783Pro), in exon 21 of the MYH7 gene, which encodes slow skeletal muscle fiber/β-cardiac myosin heavy chain protein, that replaces a highly conserved arginine with a proline. This novel mutation that results in the unusual combined cardiac and skeletal muscle phenotype localizes to the essential light chain binding area, a region only previously shown to be mutated in hypertrophic cardiomyopathy.