Familial mitochondrial encephalomyopathy with stroke-like episodes and episodic disturbances of consciousness: a study of pedigree including three generations with multisystemic abnormalities

We report here two cases in a family with pleomorphic clinical features which include mitochondrial myopathy, encephalopathy, stroke-like episodes, episodic disturbances of consciousness and other multisystemic abnormalities. The other signs observed in multisystemic abnormalities were ophthalmoplegia, short stature, diabetes mellitus, diabetes insipidus, renal dysfunction, optic atrophy, retinal degeneration, impairment of hearing and mental retardation or deterioration. A symptomatological variation was observed in cases in the same family. It is suggested that these widely varying symptoms may be expressions caused by a common biochemical defect which involves different tissues in different individuals in the family. The syndromes observed in the present cases were compared with other possibly-related mitochondrial encephalomyopathies.     

Mitochondrial and ocular myopathies (62 cases)

The authors report the clinical signs and histological findings in 62 patients with ocular myopathies divided into two groups: (a) ocular myopathies with mitochondrial abnormalities, themselves divided into pure (19 cases) or progressive (15 cases) ophthalmoplegia, and multisystemic myopathies (14 cases); (2) oculopharyngeal myopathies (15 cases) in elderly subjects, with constant intranuclear tubulofilamentous inclusions. Among myopathies with mitochondrial abnormalities, ocular forms with a favourable prognosis coexisted with earlier and more severe multisystemic lesions.     

Mitochondrial encephalomyopathy: clinical aspects, CT morphology and neuropathology

Basing on the example of two cases, the clinical and morphological variability of mitochondrial encephalomyopathies is demonstrated. Both patients were of short build, and the clinical signs and symptoms were dementia, ataxia, epilepsy and hardness of hearing, whereas signs of myopathy were very mild or absent. Computed tomography showed infratentorial pronounced atrophy of the brain and basal ganglia calcifications, in one case additionally ischemic infarctions, as can be seen in "mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes syndrome" (MELAS). A CT follow-up over 8 years with a progression of the abnormalities parallel to the progressive clinical course is demonstrated. Besides typical "ragged red fibres-myopathy" different abnormalities of mitochondria were seen by the electron microscope. One of the patients died; he had exceptional pathological-anatomical findings with mitochondrial cardiomyopathy, angioma and necrotising encephalopathy of Leigh's type. The two case reports show that in patients with such multisystemic neurological signs and CT-findings mitochondrial encephalomyopathy should be considered and a muscle biopsy should be performed.     

Ophthalmoplegia plus. A multisystem disorder of unknown etiopathogenesis

Six cases of Ophthalmoplegia Plus (OP) have been studied: all the patients had palpebral ptosis, ophthalmoparesis and descending myopathy. Hypoacusia, cardiac conduction impairment, small stature, mental deficit and vestibulo-cerebellar dysfunction were present only in some cases.EMG showed a severe slowing of motor and sensory conduction velocity in one patient. Polyphasic and long duration MU action potentials, which are indicative of a neurogenic myopathy, were found in all cases. Every muscle biopsy showed many «ragged red fibers» which, in EM, appeared to contain abnormal mitochondria.According to the literature and our data, OP appears to be a multisystemic disorder with severe muscle mitochondrial abnormalities, but it is not certain whether it must be considered a syndrome with multiple etiological factors or a single nosological entity with different possibilities of clinical manifestations.     

Findings in muscle in complex I (NADH coenzyme Q reductase) deficiency

Thirteen of 15 patients with complex I deficiency had the multisystemic form, with strokelike episodes and other symptoms that fulfilled the diagnostic requirements for MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes), and 2 had only muscle fatigability and weakness, having the purely myopathic form. In the multisystemic form, 12 patients had ragged-red fibers. All multisystemic patients had myopathic histochemical abnormalities that consisted of mild to moderate variation in fiber size, disorganized intermyofibrillar networks, type 2 fiber atrophy, and an increased number of type 2C fibers. Five of 13 multisystemic patients had decreased cytochrome c oxidase (CCO) activity in extrafusal fibers, with sparing of intrafusal muscle fibers. In the myopathic form, pathological findings were similar to those in the multisystemic form. In addition to complex I and NADH dehydrogenase activities being decreased, the CCO activity was significantly decreased (less than 50% of control value) in 8 patients, especially when the disease was in its advanced stages, suggesting that CCO enzyme might be secondarily affected as the disease progresses.     

Genetic Counseling in Mitochondrial Disease

Mitochondrial diseases are a genetically and clinically diverse group of disorders that arise as a result of dysfunction of the mitochondria. Mitochondrial disorders can be caused by alterations in nuclear DNA and/or mitochondrial DNA. Although some mitochondrial syndromes have been described clearly in the literature many others present as challenging clinical cases with multisystemic involvement at variable ages of onset. Given the clinical variability and genetic heterogeneity of these conditions, patients and their families often experience a lengthy and complicated diagnostic process. The diagnostic journey may be characterized by heightened levels of uncertainty due to the delayed diagnosis and the absence of a clear prognosis, among other factors. Uncertainty surrounding issues of family planning and genetic testing may also affect the patient. The role of the genetic counselor is particularly important to help explain these complexities and support the patient and family’s ability to achieve effective coping strategies in dealing with increased levels of uncertainty.     

Point mutation tRNA(Ser(UCN)) in a child with hearing loss and myoclonus epilepsy

We report on a family with a 12-year-old boy who suffered from a maternally inherited syndrome characterized by a combination of sensorineural hearing loss, myoclonus epilepsy, ataxia, severe psychomotor retardation, short stature, and diabetes mellitus. First, he showed a muscular hypotonia with hearing loss; later, he developed a myoclonus epilepsy, growth failure, and severe psychomotor retardation. At the age of 10 years, he developed diabetes mellitus. After initiation of combined ubiquinone and vitamin C treatment, we observed a progression in psychomotor development. Lactate and pyruvate levels in blood and cerebrospinal fluid were normal. No ragged red fibers or ultrastructural abnormalities were seen in a skeletal muscle biopsy. Biochemical assays of respiratory chain complex activities revealed decreased activity of complexes I and IV. By sequence analysis of mitochondrial DNA encoding transfer ribonucleic acids (RNAs), a homoplasmic T to C substitution at nucleotide position 7512 was found affecting a highly conserved base pair in the tRNA(ser(UCN)) acceptor stem. Asymptomatic family members of the maternal line were heteroplasmic for the mutation in blood samples. Analysis of mitochondrial DNA in patients with hearing loss and myoclonus epilepsy is recommended, even in the absence of laboratory findings. Therapeutically, ubiquinone and antioxidants can be beneficial.     

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.     

Pleomorphic mitochondrial and different filamentous inclusions in inflammatory myopathies associated with mtDNA deletions

Mitochondrial changes are frequently observed in muscle fibers of patients with inclusion body myositis (IBM) and polymyositis (PM), suggesting that mitochondrial function may be especially impaired in these forms of inflammatory myopathies. Intranuclear and cytoplasmic tubulofilamentous inclusions are characteristic, although not totally specific for IBM. In the present cases, the inclusions were strikingly pleomorphic when chloroquine had been given for long periods. The nuclear inclusions were always tubular, whereas the cytoplasmic filaments had either a tubular, a helical, or a cross-striated structure with different diameters and arrangements in association with myelin-like figures, and vacuoles. Abnormal mitochondria containing paracrystalline, globoid, and other inclusions, noted in IBM, were occasionally also seen in PM or vasculitis. By contrast, in the latter, no intranuclear or cytoplasmic tubulofilamentous inclusions were apparent in muscle fibers. This study reports for the first time the presence of membrane-bound crystalloid inclusions in a muscle fiber with numerous abnormal mitochondria; similar structures have thus far only been observed in macrophages. The identity and function of these inclusions remains unknown. Using PCR analysis we detected different mtDNA deletions not only in IBM, but also in PM and vasculitis, indicating at least some degree of association between the structural mitochondrial abnormalities and the mtDNA mutations. There was no topographical correlation between the presence of tubular or helical filaments and the mitochondrial abnormalities. As already noted by others, the mitochondrial changes in IBM were more frequent than expected in this age group. It is suggested that the presence of the mtDNA deletions in IBM and PM are not primary, but rather the result of the underlying, presumably immunological disorder causing nuclear and secondary or simultaneous mitochondrial changes. Received: 12 May 1997 / Revised, accepted: 17 February 1998     

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.     

Mitochondrial abnormalities in human sural nerves: fine structural evaluation of cases with mitochondrial myopathy,hereditary and non-hereditary neuropathies,and review of the literature

Summary Fifteen cases of mitochondrial myopathy, three cases of hereditary motor and sensory neuropathy (HMSN) VI, and 280 cases of neuropathies of different etiologies were examined by electron microscopy for the presence of mitochondrial abnormalities in the sural nerve. Altered mitochondria were found in most cases of mitochondrial myopathy, in all cases of HMSN VI, and in 25 cases out of the series of unselected neuropathies. The mitochondrial changes comprised enlargement with an amorphous matrix and distorted cristae, with hexagonal paracrystalline inclusions, and with prominent cristae containing oblique striations, and a variety of rare changes. Most mitochondrial abnormalities were found in Schwann cells. An increase of the number of mitochondria was noted in smooth muscle and endothelial cells of epineurial arterioles of two cases with mitochondrial encephalomyopathy. Neuropathy was present in all cases of mitochondrial myopathy according to morphometrical analysis. Whether neuropathy is caused directly by mitochondrial dysfunction or by other pathogenetic mechanisms remains to be determined.Presented in part at the 9th meeting of the Peripheral Nerve Study Group, Praglia, Italy, August 31–September 2, 1989, and at the 9. Kongreß des wissenschaftlichen Beirates der DGBM über neuromuskuläre Erkrankungen, Hamburg, Germany, September 21–23, 1989     

Mitochondrial dysfunction in patients with hypotonia,epilepsy, autism,and developmental delay: HEADD syndrome

A group of 12 children clinically presenting with hypotonia, intractable epilepsy, autism, and developmental delay, who did not fall into previously described categories of mitochondrial encephalomyopathy, were evaluated for mitochondrial respiratory enzyme activity levels, mitochondrial DNA, and mitochondrial structural abnormalities. Reduced levels in specific respiratory activities were found solely in enzymes with subunits encoded by mitochondrial DNA in seven of eight biopsied skeletal muscle specimens evaluated. Five cases exhibited increased levels of large-scale mitochondrial DNA deletions, whereas pathogenic point mutations previously described in association with mitochondrial encephalomyopathies were not found. Mitochondrial structural abnormalities were present in three of four patients examined. Our findings suggest that mitochondrial dysfunction, including extensive abnormalities in specific enzyme activities, mitochondrial structure, and mitochondrial DNA integrity, may be present in children with a clinical constellation including hypotonia, epileptic seizures, autism, and developmental delay. The acronym HEADD is presented here to facilitate pursuit of mitochondrial defects in patients with this clinical constellation after other causes have been excluded.     

The POEMS syndrome among Chinese: association with Castleman''s disease and some immunological abnormalities

POEMS or Crow-Fukase syndrome is a multisystemic, clinically malignant disorder of obscure etiology. Peripheral neuropathy and plasma cell dyscrasia are central features. The authors now report 7 Chinese patients with this syndrome in which PCD or paraproteinemia were absent in 6, and 2 had a lymph node histology resembling that of hyaline-vascular Castleman's disease. Immunological abnormalities consisted of either increased or decreased numbers of B- and T-cells in 2 cases, and an elevated OKT4/OKT8 ratio with paradoxical dissociation of the lymphocyte transformations to various concentrations and types of mitogens in 1 case. This suggests that the underlying abnormalities of POEMS syndrome are heterogeneous and that it may be an immunologically related syndrome of varying etiology.     

Exploration of exercise intolerance by 31P NMR spectroscopy of calf muscles coupled with MRI and ergometry

One hundred patients presenting with exercise intolerance or rhabdomyolysis episodes have been examined successively by 31P Nuclear Magnetic Resonance Spectroscopy (MRS) of leg plantar flexor muscles with exercise test. In all cases a muscle biopsy was performed. At the end of investigations, diagnosis of a metabolic myopathy was made in 33 patients: glycogenolysis or glycolysis deficiency in 8 cases, mitochondrial myopathy in 24 cases and CPT II deficiency in one case. Muscular dystrophy or congenital myopathy were diagnosed in 6 cases. No precise etiology could be found in 30 patients with either high CK levels or muscle biopsy abnormalities. Seven patients had rhabdomyolysis related to excessive physical activities. Twenty-four patients had functional symptoms. The principal MRS parameters used for diagnosis were the values of intracellular pH at the end of exercise and the time constant of phosphocreatine resynthesis during recovery. Lack of acidosis after exercise was observed in all patients with blockade of glycogenolysis or glycolysis. A slowing in phosphocreatine resynthesis was found in 66 p.cent of patients with definite mitochondrial myopathy. The specificity of these parameters were respectively 92.4 p.cent and 85.5 p.cent for the two groups. In conclusion (31)P MRS allows the detection of muscular glycogenoses with a sensitivity close to 100 p.cent. However, its sensitivity was lower for the detection of mitochondrial myopathies, as is also known for the other in vivo metabolic investigations, reflecting the heterogeneity of expression of mitochondrial abnormalities in a given muscle. The integration of imaging in the examination protocol may help to orientate towards the diagnostic of a dystrophy in some patients.     

Familiäre mitochondriale chronisch progressive externe Ophthalmoplegie Fünf Familien mit unterschiedlicher Genetik

Chronic progressive external ophthalmoplegia (CPEO) is considered the most frequent form of mitochondrial encephalomyopathies. Most cases occur sporadically. We investigated 18 consecutive patients with CPEO. Thirteen cases were sporadic and five cases were familial. In one family with maternal inheritance the mitochondrial point mutation A3243G was identified. In index patients of three other families multiple deletions of mitochondrial DNA were found. One of these families showed autosomal recessive inheritance. In the two other pedigrees a definitive determination of the mode of inheritance was impossible. The fifth family revealed autosomal dominant or maternal inheritance. In their index patient no alteration of mitochondrial DNA could be identified (including sequencing of hot spots for mitochondrial mutations). CONCLUSIONS: CPEO was familial in 28% of our patients. There are three different modes of inheritance: (i) maternal transmission associated with mitochondrial point mutations as it is known for other mitochondrial disorders, (ii) autosomal recessive, and (iii) autosomal dominant inheritance. In contrast to sporadic cases with single mitochondrial deletions autosomal inheritance can be associated with multiple deletions of mitochondrial DNA. They are due to so far unknown nuclear mutations.     

Dysarthria,progressive parkinsonian features and symmetric necrosis of putamen in a family with painful lipomas (Dercum disease variant)

We describe painful subcutaneous lipomatosis in four members of a two-generation family. Lipomas appeared in adulthood, were circumscribed, painful on touch and mainly localized to the trunk and proximal parts of the extremities. The disorder was associated with dysarthria, visual pursuit defect and progressive dystonia. MRI showed bilateral increasing cystic lesions in the basal parts of the putamen. No other abnormalities were detected. The lesions corresponded well with the clinical presentation in the patients. Investigation for mitochondrial disease with muscle biopsy and mitochondrial DNA gave normal results. No consistent biochemical changes were found. The disorder in this family was considered to differ from MERRF with lipomatous lesions and multiple symmetric lipomatosis but compatible with a Dercum disease variant.     

以肌无力伴水肿为主要表现的线粒体肌病1例报告并文献复习

目的：通过相关病例及文献复习探讨线粒体肌病的临床特征、辅助检查所见特点及治疗进展情况。方法：回顾贵州医科大学附属医院收治的1例线粒体肌病患者的临床资料,结合相关文献进行分析。结果：线粒体肌病以波动性的肌无力、肌肉疼痛为主要临床特征,可伴有眼外肌、心肌,甚至自主神经系统的损害,血清肌酸激酶轻至中度升高,肌肉活检病理特点为改良 Gomori T richrome染色（MGT）可见破碎红纤维,电子显微镜下线粒体数目和形态异常,并可见典型的结晶样包涵体。结论：线粒体肌病是一类以肌无力为特点伴多系统损害的遗传性疾病,以肌肉活检病理检查和相关基因检测为主要确诊依据。对于存在肌无力伴多系统损害症状的患者,应警惕此病的可能。     

线粒体脑肌病的临床、病理与神经电生理

目的探讨线粒体脑肌病的临床、肌肉病理及神经电生理特点，以便早期诊断。方法对6例确诊的线粒体脑肌病患者的临床表现、肌肉组织光镜和超微结构改变以及神经电生理改变进行了回顾性分析。结果本组患者的临床特征主要以运动不耐受，阵挛、抽搐发作，精神障碍，共济失调为主。6例患者中4例发现破碎红纤维（RRF），其平均比例为5．3％；超微结构观察有线粒体异常及糖原颗粒沉积，其中有2例发现有典型晶格状包涵体。以癫痫发作为主要临床表现的患者脑电图明显异常；肌电图以神经源性改变4例，占本组病例的4／6；听觉诱发电位（BAEP）、体感诱发电位（SEP）异常3例，占3／6。结论线粒体脑肌病的临床表现复杂多样，诊断主要依赖于临床特征分析和肌肉活检；电镜超微结构改变为线粒体病的主要诊断依据；神经电生理改变对病理损伤累及范围和程度方面有一定的参考价值。     

Familial indifference to pain with somatosensory asymmetry: possible central anomaly

A family of seven siblings is described. The mother and six siblings have been examined, the eldest and youngest of whom suffer from congenital indifference to pain , although both were ticklish, and itched. The functions examined included somatosensory perception thresholds and autonomic functions; perception thresholds were greatly raised in the painfree subjects and to a lesser extent in some other family members, asymmetrically in all cases, being higher in the dominant hand. Painfree Subject 1 also underwent cerebrospinal fluid analysis at age 16, which showed normal B-endorphin levels but undetectable enkephalins. Electrophysiological tests when a child demonstrated notably that most (raised) measured values were lowered by naloxone. Light microscopic sural nerve biopsy performed on painfree Subject 1 in childhood did not suggest any abnormalities other than a thickened nerve sheath. Threshold asymmetry has not been observed in large numbers of subjects without neurological deficits. There were no significant autonomic changes in any tested family member, though there was some asymmetry. It is suggested that the findings may imply a congenital anomaly of the central nervous system which accounts for the somatosensory, biochemical, and electrophysiological abnormalities.     

Evaluation of renal parathyroid hormone receptor function in myotonic dystrophy

Endocrine abnormalities in myotonic dystrophy (MyD) reflect some of the multisystemic involvement resulting from this disorder. One of these, abnormal insulin secretion, is considered to be caused by receptor dysfunction. Bone abnormalities, cataract and calcium transport defect suggest the abnormal calcium metabolism in MyD. The calcium metabolism is chiefly regulated by parathyroid hormone (PTH). An interest in the similarity between MyD and pseudohypoparathyroidism, which is a disorder of PTH receptor dysfunction, encouraged the authors to evaluate renal PTH receptor function from the responses of urinary adenosine 3′,5′-monophosphate (cAMP) and phosphate excretion after administration of human PTH(1–34). The responses of cAMP were high in 3 cases, low in one case, but normal in the 4 other cases. The phosphaturic responses were elevated in 3 cases, reduced in 3 cases, and normal in 2 other cases. Since these abnormal responses closely mimic those in hypoparathyroidism, there may also be renal PTH receptor dysfunction in some cases of MyD. The results of the present study suggest another peptide hormone receptor defect, similar to insulin, which supports the hypothesis of generalised receptor dysfunction in MyD.