Muscle-nerve involvement in autosomal dominant progressive external ophthalmoplegia with hypogonadism

Sixteen members of a family with a history of autosomal dominant progressive external ophthalmoplegia (adPEO) with hypogonadism were examined. The muscular involvement commenced cranially and descended in relation to increasing disease duration. The neuromuscular signs were PEO, dysarthria, dysphonia, limb muscle weakness with wasting, absence of Achilles tendon reflexes, and distal vibration sensory loss. The electromyogram (EMG) was myopathic in facial and proximal limb muscles. Neurogenic involvement was suspected in a few tibial anterior muscles. Neurography showed signs of axonal neuropathy correlated to clinical signs. F-responses were reduced in number or absent in peroneal nerves, and did not correlate to clinical signs or disease duration. Muscle biopsies in advanced cases had structural abnormalities of mitochondria, ragged-red fibers, and focal cytochrome c oxidase deficiency. A combination of muscle-nerve involvement with PEO, Achilles tendon areflexia, distal vibration sensory impairment, myopathic EMG, and abnormally low sural nerve responses seems to be typical of this type of mitochondrial disorder. © 1996 John Wiley & Sons, Inc.     

Multimodal evoked potentials in progressive external ophthalmoplegia with mitochondrial myopathy

Multimodal evoked potentials were studied in 13 patients affected by progressive external ophthalmoplegia with histologically proven mitochondrial myopathy. Progressive external ophthalmoplegia occurred with craniosomatic spreading in all the patients and with a varying degree of nervous and/or other system involvement in most of them. In all but one of the subjects, at least one evoked potential modality was abnormal; 11 of them demonstrated an abnormal visual evoked potential, but this finding might have been influenced by concurrent retinal dysfunction. Abnormalities in brainstem auditory evoked potentials and/or somatosensory evoked potentials, revealing an impairment of central sensory pathways, were detected in 7 subjects, 5 of whom lacked clinical evidence of central nervous system involvement. Thus, evoked potentials represent an useful tool for the detection of subclinical central nervous system involvement in patients affected by progressive external ophthalmoplegia with mitochondrial myopathy.     

Frequency of dystrophic muscle abnormalities in chronic progressive external ophthalmoplegia: analysis of 86 patients

BACKGROUND: There are few reports describing the coexistence of dystrophic features with those typical of mitochondrial myopathies in muscle biopsy. A recent study suggested that dystrophic features are frequent in patients with chronic progressive external ophthalmoplegia (CPEO) with a high mutation load, but the actual frequency of these abnormalities in CPEO remains undetermined. OBJECTIVE: To review the occurrence of dystrophic abnormalities in a large series of patients with CPEO to assess the frequency of such abnormalities and to verify whether they are correlated with specific mitochondrial DNA (mtDNA) mutations. METHODS: Retrospective survey of case series (86 patients with CPEO). RESULTS: Only three cases with dystrophic abnormalities were found: two with a large scale mtDNA deletion and one with the A3251G mutation. All three patients showed predominantly proximal muscular weakness resembling limb girdle muscular dystrophy. CONCLUSIONS: Dystrophic abnormalities are rare in CPEO and are not correlated with a specific molecular defect.     

Muscle fatigue,lactate, and pyruvate in mitochondrial myopathy with progressive external ophthalmoplegia

We studied muscle fatigue and serum lactate and pyruvate levels in 20 patients with mitochondrial myopathy with progressive external ophthalmoplegia (PEO). Fatigue was assessed in the adductor pollicis muscle (AP) using a low-intensity exercise protocol (20 min). Forces (TFs) and relaxation times of ulnar nerve evoked twitches, compound muscle action potentials (CMAPs), and maximal voluntary contractions (MVCs) were monitored. Serum lactate and pyruvate levels were independently measured at rest and after exercise on a bicycle (15 min, 30 W). Most patients showed abnormal fatigue of the AP with a reduction of TFs and MVCs and normal CMAPs. The reduced TFs were significantly correlated with lactate levels at rest (r = −0.60, P < 0.05) and less so with those after exercise (r = −0.47, P < 0.05). Pyruvate levels revealed a similar correlation although they were widely scattered. We conclude that abnormal fatigue in PEO is metabolic, is localized beyond the muscle fiber membrane, and involves the electromechanical coupling and the contractile apparatus. Serum lactate levels at rest are good predictors of fatigue in PEO. © 1996 John Wiley & Sons, Inc.     

慢性进行性眼外肌瘫痪的临床和病理学特点

目的探讨慢性进行性眼外肌瘫痪(CPEO)的临床和病理学特点。方法回顾性分析7例CPEO患者的临床资料。结果本组7例患者均有不同程度的双侧眼睑下垂,6例有明显的眼球活动障碍。1例患者在发病16年后出现吞咽费力和肢体肌力下降。7例患者肌电图检查示,1例患者部分被检肌呈神经源性损害。7例患者肌肉活检均可见破碎红边纤维(RRF),其中2例伴有部分肌纤维脂质增多,2例患者显示Ⅰ、Ⅱ型纤维分布异常,可见群组化现象。本组有2例患者行电镜检查示肌膜下和肌原纤维间有异常线粒体聚集。结论 CPEO是一种以慢性进行性眼睑下垂和眼球运动障碍为主要临床表现的线粒体脑肌病,临床上容易误诊为眼肌型重症肌无力、眼咽型肌营养不良症和眼科疾病。骨骼肌活检病理检查发现RRF或异常线粒体聚集,是确诊本病的重要依据。     

Clinical phenotype of autosomal dominant progressive external ophthalmoplegia in a family with a novel mutation in the C10orf2 gene

Autosomal dominant progressive external ophthalmoplegia (adPEO) is a mitochondrial disorder caused by mutations in nuclear genes. Here we report the clinical and genetic features of adPEO in a Chinese family. All patients had gradual onset of ptosis, with or without ophthalmoplegia, around age 30. Thirteen patients had limb weakness around age 40. Eight patients developed dysphagia around age 50. Four patients died of cardiac abnormalities around age 60. Muscle biopsy of the proband indicated mitochondrial myopathy characterized by ragged‐red fibers, cytochrome c oxidase‐negative fibers, and multiple deletions of mitochondrial DNA. A heterozygous missense mutation of c.1342A>G in the C10orf2 gene resulting in the p.448N>D mutation in the protein was found in the proband and four other affected family members. In summary, we identified an adPEO family with a novel C10orf2 gene mutation that manifested an age‐dependent phenotype. It suggests that greater attention must be paid to cardiac abnormalities in the late stages of this disease. Muscle Nerve, 2010     

Lack of apoptosis in patients with progressive external ophthalmoplegia and mutated adenine nucleotide translocator-1 gene

Adenine nucleotide translocator-1 (ANT-1), encoded by chromosome 4 (4q34-35 locus), is a component of the mitochondrial permeability transition pores that are involved in apoptotic mechanisms. We studied muscle biopsies from seven individuals with autosomal dominant progressive external ophthalmoplegia caused by ANT-1 mutations. We found no instance of terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling (TUNEL) positivity nor significant expression of apoptosis-related proteins. Furthermore, there was no morphological evidence of apoptosis at the ultrastructural level. Thus, degeneration of muscle in this disorder is nonapoptotic.     

慢性进行性眼外肌瘫痪的临床和病理学特点

目的探讨慢性进行性眼外肌瘫痪(CPEO)的临床和骨骼肌病理学特点。方法回顾性分析6例CPEO患者的临床及病理资料。结果6例CPEO患者4~18岁起病,首发症状为眼睑下垂,主要临床表现为眼球活动受限,并有肢体易疲劳、无力,血清肌酸激酶轻到中度升高;5例肌电图呈肌源性损害。肌肉病理学检查可见散在的破碎红纤维(RRF),细胞色素C氧化酶(COX)活性减低/缺失;4例患者可见少量变性、坏死肌纤维;3例油红"O"染色见脂滴增多;电镜下可见肌纤维膜下、胞浆中线粒体数量增多、聚集,形态异常,可有结晶状的包涵体。结论CPEO临床主要表现为眼外肌瘫痪合并肢体肌无力;骨骼肌病理显示大量RRF及COX活性减低/缺失提示和支持CPEO的诊断;CPEO确诊需在骨骼肌病理诊断基础上行基因测序。     

A partial deficiency of cytochrome c oxidase in chronic progressive external ophthalmoplegia

A partial deficiency of cytochrome oxidase has been found in 7 patients with chronic progressive external ophthalmoplegia and proximal myopathy or craniosomatic abnormalities. Muscle biopsies from all these patients showed morphological mitochondrial abnormalities (“ragged red” fibres) and cytochemical assay of cytochrome oxidase showed that these fibres contained no demonstrable enzyme activity. The incidence of cytochrome oxidase-negative fibres was greater than that of “ragged-red” fibres suggesting that the enzyme defect preceded the development of morphological mitochondrial changes. Biochemical analysis of skeletal muscle mitochondrial fractions from 3 patients revealed in 1 case a significantly lower concentration of cytochrome aa₃ and a decreased ratio of cytochrome oxidase/succinate-cytochrome c reductase. Fasting blood metabolites were elevated in 2 patients. We suggest that partial cytochrome oxidase deficiency is the underlying defect in mitochondrial myopathy associated with the oculocraniosomatic syndromes.     

Cardiac screening investigations in adult‐onset progressive external ophthalmoplegia patients

Introduction: Patients with mitochondrial myopathies may develop cardiac complications such as cardiomyopathy and/or cardiac conduction defects. To identify these potentially life‐threatening and treatable conditions, it is common practice to screen patients intermittently with electrocardiography and echocardiography. The optimal time interval for such screening investigations is unknown. We developed this study to review our screening results in adult‐onset patients with progressive external ophthalmoplegia (PEO). Methods: This study was a retrospective review of PEO patients with 5 years or more of cardiac screening investigations who did not have any cardiac symptoms. Results: Fifteen patients were included, and cardiomyopathy was identified on screening echocardiogram in 1 patient. Four patients had other abnormalities identified, which were unrelated to their mitochondrial myopathy. Conclusions: Only 1 patient in 15 developed cardiac complications related to mitochondrial disease during 5 years of follow‐up. We suggest that a screening interval of 3–5 years is probably appropriate for adult‐onset PEO patients who do not have cardiac symptoms. Muscle Nerve 60: 608–611, 2012     

Two families with autosomal dominant progressive external ophthalmoplegia

OBJECTIVES: We report here the clinical and genetic features of two new families with autosomal dominant progressive external ophthalmoplegia (adPEO). PATIENTS AND METHODS: The examination of index patients included a detailed clinical characterisation, histological analysis of muscle biopsy specimens, and genetic testing of mitochondrial and nuclear DNA extracted from muscle and leucocytes. RESULTS: Index patients in both families presented with PEO and developed other clinical disease manifestations, such as myopathy and cardiomyopathy (patient 1) and axonal neuropathy, diabetes mellitus, hearing loss, and myopathy (patient 2), later in the course of illness. Both patients had ragged red fibres on muscle histology. Southern blot of mtDNA from muscle of patient 2 showed multiple deletions. In this case, a novel heterozygous missense mutation F485L was identified in the nuclear encoded putative mitochondrial helicase Twinkle. The mutation co-segregated with the clinical phenotype in the family and was not detected in 150 control chromosomes. In the other index patient, sequencing of ANT1, C10orf2 (encoding for Twinkle), and POLG1 did not reveal pathogenic mutations. CONCLUSIONS: Our cases illustrate the clinical variability of adPEO, add a novel pathogenic mutation in Twinkle (F485L) to the growing list of genetic abnormalities in adPEO, and reinforce the relevance of other yet unidentified genes in mtDNA maintenance and pathogenesis of adPEO.     

Sleep disturbances in chronic progressive external ophthalmoplegia

Background: Chronic progressive external ophthalmoplegia (CPEO) is a relatively common mitochondrial disorder. In addition to extraocular muscle weakness, various other organs can typically be affected, including laryngeal and limb muscles, cerebrum, cerebellum, and peripheral nerves. Given this multi‐organ involvement, patients are likely to be prone to sleep disturbances. Here, we determined the nature, prevalence, and determinants of sleep disturbances in CPEO. Methods: We used validated questionnaires for various sleep disorders and possible determinants such as mood and anxiety, and we performed ambulant polysomnography (PSG) in 20 patients with genetically confirmed CPEO. Results: Three quarters of patients reported nocturnal sleep dysfunction. Thirty‐five percent of patients fulfilled the criteria for restless legs syndrome, 30% excessive daytime sleepiness, and 70% significant periodic limb movements. PSG recordings revealed several indicators of a disrupted sleep architecture. Obstructive sleep disordered breathing was present in only one patient. However, four patients had an increased central sleep apnea index, all of whom had a polymerase gamma‐1 mutation and a SANDO phenotype (sensoric atactic neuropathy, dysarthria, ophthalmoplegia). Physical examination and questionnaire outcomes were poor predictors of PSG results. Conclusion: Several specific sleep disturbances are part of the phenotype of CPEO. Given that the disease is otherwise incurable, symptomatic treatment of sleep disturbances may be an important tool to improve quality of life. Therefore, patients with CPEO should be actively screened for sleep disorders, with a low threshold to perform PSG.     

TWINKLE gene mutation: report of a French family with an autosomal dominant progressive external ophthalmoplegia and literature review

Background: Multiple mitochondrial DNA (mtDNA) deletions usually have a mendelian inheritance secondary to mutation in nuclear genes. One of these is the Twinkle gene whose mutation is responsible for autosomal dominant progressive external ophthalmoplegia (PEO). The number of reported cases with mainly myopathic symptoms and possible nervous system involvement related to Twinkle gene mutation is limited. We present a new French family of whom two members displayed myopathy and neuropathy associated with PEO, and we perform a clinical review in light of other observations reported in the literature. Methods: The proband, one son and the daughter have been investigated. Southern blot analysis and long‐range PCR assay have been performed from muscle biopsy specimens. Coding exons and flanking intron regions of polymerase gamma (POLG) and DNA helicase (Twinkle) genes were sequenced. Results: Multiple mitochondrial DNA deletions have been found and sequencing of the Twinkle gene showed the change p.R374Q. Conclusion: Two other families from the literature also had the R374Q mutation. Symptoms reported in association with this mutation were myopathy, peripheral neuropathy, dysarthria and/or dysphagia, respiratory insufficiency and parkinsonism. Respiratory insufficiency caused by chest wall weakness was reported in other families with different Twinkle gene mutations, and one might provide exercise intolerance, dysarthria and/or dysphagia as symptoms in favor of the diagnosis. Occurrence of impressive emaciation was a peculiarity in our family.     

慢性进行性眼外肌麻痹的临床和病理研究

目的总结慢性进行性眼外肌麻痹(CPEO)的临床和病理特点。方法回顾分析2015年10月至2017年7月于我院确诊的5例CPEO患者的临床及骨骼肌病理特点。结果男性2例,女性3例,均为散发病例,平均起病年龄(27.8±12.56)岁(15～51岁)。4例首发症状为眼睑下垂,1例为复视。5例均有眼睑下垂及眼球活动障碍,2例伴复视,1例有轻度颈屈肌和四肢近端肌无力,1例19岁月经初潮且身体矮小。5例新斯的明试验及血清乙酰胆碱受体抗体均阴性。仅1例肌酸激酶(CK)水平轻度升高(251 U/L)。1例心电图完全性右束支传导阻滞。5例均行肌电图检查,其中2例部分被检肌呈肌源性改变,5例重复神经电刺激均正常。5例头颅MRI均正常。骨骼肌病理改变主要为异常增多的破碎红纤维(RRF)、破碎蓝纤维(RBF)和细胞色素C氧化酶(COX)阴性肌纤维。结论 CPEO患者主要临床特点为进行性眼睑下垂和眼球活动障碍,少数患者可伴复视或轻微肢体近端肌无力、心脏传导阻滞和发育迟缓等。主要诊断措施为骨骼肌病理可见异常增多的RRF和COX阴性肌纤维。     

Disease impact in chronic progressive external ophthalmoplegia: more than meets the eye

We determined the extent of disease impact in 28 patients with genetically confirmed chronic progressive external ophthalmoplegia (CPEO) and compared the outcomes to those of matched myotonic dystrophy type I patients.CPEO patients reported a high frequency of severe fatigue (67.9%), pain (96.2%), depression (32.1%) and dependency in daily life (46.4%). The frequency and extent of depression were significantly higher than in DM1 patients (32.1% vs. 7.1%, p = 0.040; mean Beck’s depression inventory for primary care score 3.8 ± 3.5 vs. 1.3 ± 1.4, p = 0.001), as were fatigue severity, pain intensity and extent of functional impairments.CPEO patients with polymerase gamma-1 mutations reported more functional impairments than those with mitochondrial DNA mutations. Disease impact was however not influenced by most clinical features. The present results help physicians to identify and to treat the factors that influence quality of life in CPEO patients and to provide symptomatic treatment where needed.     

Skeletal muscle pathology in chronic progressive external ophthalmoplegia with ragged-red fibers

Summary Histochemical investigations were carried out on skeletal muscle biopsies from ten patients with chronic progressive external ophthalmoplegia with ragged-red fibers (RRF). In addition to the RRF, mild myopathic change consisting of variation in size of both type 1 and 2 fibers was seen in all patients, as well as neuropathic change in eight. Scattered fibers with absent cytochromec oxidase (CCO) activity (focal deficiency) were seen in all patients. In serial sections, CCO deficiency did not always occupy the entire length of a fiber but was localized segmentally to regions measuring several hundred micrometers in lenghth, suggesting the heterogeneity of CCO activity even in the same fiber.This work was partially supported by a Grant-in-Aid for Scienctific Research on Priority Areas (No. 626/7523) from the Ministry of Education, Science and Culture of Japan.     

A novel mitochondrial DNA deletion producing progressive external ophthalmoplegia associated with multiple sclerosis

We report a previously undescribed 7676 base pair mitochondrial (mt)DNA deletion involving genes of complex I, complex IV subunits 2 and 3 (cytochrome oxidase [Cox] II, III), adenosine triphosphatase 8 and 6, cytochrome b and 8 transfer (t)RNA genes producing myopathy and progressive external ophthalmoplegia (PEO) in a 44-year-old right-handed Caucasian man with features of multiple sclerosis (MS). We performed complete mtDNA sequencing and deletion analysis, spectrophotometric analysis of muscle and platelet respiratory chain activity, measurement of platelet mitochondrial membrane potential with the potentiometric dye JC-1 and magnetic resonance spectroscopy (MRS) and MRI studies of normal-appearing and lesional cerebral tissue. The deletion resulted in significant respiratory chain deficiency in muscle and blood and abnormalities of the platelet mitochondrial membrane potential. However, cerebrospinal fluid analysis, magnetic resonance spectroscopy and MRI features suggested inflammatory central nervous system demyelination rather than a primary respiratory chain disorder. We conclude that this novel mtDNA deletion causing myopathy and PEO is associated with severe muscle and platelet cellular energetic abnormalities. Furthermore, clinical and paraclinical features of multiple sclerosis were found. The potential pathomechanistic interaction between mtDNA variation and multiple sclerosis is reviewed.     

Twinkle mutations in two Chinese families with autosomal dominant progressive external ophthalmoplegia

Autosomal dominant progressive external ophthalmoplegia (adPEO) is a common adult onset mitochondrial disease caused by mutations in nuclear DNA (nDNA). Twinkle is one of the nuclear genes associated with adPEO. Clinical, histochemical, and molecular genetics findings of 6 patients from two Chinese families with adPEO were reported. Two point mutations (c.1423G>C, p.A475P and c.1061G>C, p.R354P) of Twinkle gene have been found. Multiple mtDNA deletions were also detected in patient’s muscle and fibroblasts. This study confirms two mutations in Chinese adPEO families, which were first reported in the Chinese population.     

A novel Twinkle gene mutation in autosomal dominant progressive external ophthalmoplegia

Autosomal dominant progressive external ophthalmoplegia is a common neurological presentation of mitochondrial disease and is characterised by multiple deletions of mitochondrial DNA in muscle. We describe a family with autosomal dominant progressive external ophthalmoplegia caused by a novel heterozygous A to C transversion at nucleotide 956 of the Twinkle gene. The deltoid muscle biopsy of the index case revealed sparse respiratory deficient cells. Multiple mitochondrial DNA deletions were clearly evident in the index case by both long-range and real-time polymerase chain reaction assays but not by Southern blotting, highlighting the diagnostic difficulties associated with characterising patients with multiple mitochondrial DNA deletions.