Hereditary motor neuron disease in a large Norwegian family with a "H46R" substitution in the superoxide dismutase 1 gene

Mutant genes associated with Charcot Marie Tooth type 2, distal hereditary motor neuropathy and familial amyotrophic lateral sclerosis may cause overlapping clinical phenotypes. We performed whole genome linkage analysis, haplotype analysis, sequencing and detailed clinical and neurophysiological investigations in a large Norwegian kindred with a condition that clinically had been classified as Charcot Marie Tooth type 2. The mutation c.140A>G, p.His47Arg (alias p.His46Arg or H46R) in the superoxide dismutase 1 gene (SOD1) segregated with the disease. The patients present a hereditary motor neuropathy-like clinical picture and long survival (mean 29years). To our knowledge, this is the first extensive report describing a large non-Japanese kindred. The prognostic implications of the condition seen in this family have little in common with what is normally associated with sporadic amyotrophic lateral sclerosis and illustrates the complexity of the genetic etiology of lower motor neuron disease.     

Coenzyme Q10 is frequently reduced in muscle of patients with mitochondrial myopathy

Coenzyme Q₁₀ (CoQ₁₀) deficiency has been associated with an increasing number of clinical phenotypes. Whereas primary CoQ₁₀ defects are related to mutations in ubiquinone biosynthetic genes, which are now being unraveled, and respond well to CoQ₁₀ supplementation, the etiologies, and clinical phenotypes related to secondary deficiencies are largely unknown.The purpose of this multicenter study was to evaluate the frequency of muscle CoQ₁₀ deficiency in a cohort of 76 patients presenting with clinically heterogeneous mitochondrial phenotypes which included myopathy among their clinical features. A reliable diagnostic tool based on HPLC quantification was employed to measure muscle CoQ₁₀ levels. A significant proportion of these patients (28 over 76) displayed CoQ₁₀ deficiency that was clearly secondary in nine patients, who harbored a pathogenic mutation of mitochondrial DNA. This study provides a rationale for future therapeutic trials on the effect of CoQ₁₀ supplementation in patients with mitochondrial diseases presenting with myopathy among clinical features.     

Survival pattern and cause of death in patients with multiple sclerosis: results from an epidemiological survey in north east Scotland.

The mean survival period in a series of 216 multiple sclerosis deaths, which formed part of a large prevalence sample observed in the Grampian region of Scotland, was 24.5 years, with an insignificant difference between females (25.7 years) and males (23.5 years). A third of the patients survived for over 30 years after onset. The age at death ranged between 25-80 years, with majority of the deaths occurring in the seventh decade (37%). On comparing life expectancy with the Scottish general population using life tables, only a slight reduction in the short-term (less than 10 years from onset) survival was noted in all age groups, with the exception of those with onset over the age of 50 years. The long-term life expectancy was however markedly reduced in all age groups compared with the controls. The survival period could be accurately predicted from the degree of disability at a point in time, and could be correlated with a number of clinical features, the most important of which was the age at onset. Eighty five per cent of those with onset of multiple sclerosis over the age of 50 years died within 20 years. Patients with a cerebellar disturbance at onset survived the shortest, and those with a brainstem lesion or retrobulbar neuritis the longest; those with a pyramidal dysfunction had an intermediate prognosis. Other parameters which could be correlated with the survival were: the timing and frequency of occurrence of psychiatric and urinary symptoms, interval between onset and first relapse and the course of the disease. As expected, most patients (89%) were significantly disabled (unable to walk) prior to death, only a minority, however, had become so within 10 years of the onset (10%). Sixty two per cent of the patients died of complications of multiple sclerosis. No unusual excess of any disease was noted amongst other causes. As expected, the majority of patients (55%) had bronchopneumonia as the terminal event, 11% had septicaemia, 15% had myocardial infarction and 4% had documented pulmonary embolism. This is the largest series of its kind where prognosis, judged by survival period, has been assessed amongst all multiple sclerosis patients derived from a prevalence sample and observed till death.     

Single deletions in mitochondrial DNA--molecular mechanisms and disease phenotypes in clinical practice

Over 20 years ago single clonal deletions were the first mitochondrial DNA (mtDNA) genetic defects described in association with human disease. Since then very large numbers of children and adults harbouring such deletions have been described and it is clear they are an important cause of human mitochondrial disease. However, there still remain many important challenges in relation to our understanding of mechanisms leading to deletion formation and propagation and in relation to the factors determining the complex and varying relationship between genotype and clinical phenotype. Although multidisciplinary team care is essential and can improve quality of life and outcomes for patients, a definitive molecular treatment for single mtDNA deletions remains an important translational research goal. Patients with mtDNA deletions exhibit a very wide range of different clinical phenotypes with marked variation in age at onset and disease severity. Single mtDNA deletions may enter into the differential diagnosis of many different paediatric and adult presentations across a wide range of medical specialties, although neurological presentations are amongst the most common. In this review, we examine the molecular mechanisms underpinning mtDNA replication and we consider the hypotheses proposed to explain the formation and propagation of single large-scale mtDNA deletions. We also describe the range of clinical features associated with single mtDNA deletions, outline a molecular diagnostic approach and discuss current management including the role of aerobic and resistance exercise training programmes.     

Different phenotypes of Friedreich's ataxia within one 'pseudo-dominant' genealogy: relationships between trinucleotide (GAA) repeat lengths and clinical features

We examined a large Turkmen family with 'pseudo-dominant' inheritance of Friedreich's ataxia resulting from consanguineous marriage of a Friedreich's ataxia patient to a heterozygote carrying an ancestral mutated allele. Two distinct phenotypes of the disease co-segregated within this genealogy. Two brothers from the younger generation exhibited 'classical' Friedreich's ataxia with onset of symptoms before 10 years and a rapidly progressive course. In contrast, three patients (two sisters from the younger generation and their father) had a more benign phenotype of late-onset Friedreich's ataxia with the onset at 26, 45 and 48 years and slow progression over decades. The patients with 'classical' Friedreich's ataxia were homozygous for a common ancestral expanded allele of the X25 gene containing 700-800 GAA repeats, while the patients with late-onset Friedreich's ataxia had two different mutated alleles, the shorter 250-repeat expansion of paternal origin and the longer 700-repeat expansion of maternal origin. One may conclude that clinical variability of Friedreich's ataxia in our patients is accounted for predominantly by a modifying effect of one of the two (shorter or longer) expanded alleles inherited from their affected father. Our observation clearly demonstrates the significance of variable-sized alleles for the phenotypic expression of the disease.     

A follow up study of patients with paraneoplastic neurological disease in the United Kingdom

OBJECTIVES: To examine the range of clinical phenotypes, tumour associations, relevant investigations, response to therapy and outcome in a large series of non-selected patients with paraneoplastic neurological disease (PND) affecting the central nervous system (CNS) in the United Kingdom. METHODS: Data were obtained on patients either through direct referral or through the British Neurological Surveillance Unit (BNSU) from February 2000 to January 2001. Physicians were asked to supply information about age and sex of patients, presenting neurological syndromes, the basis of the diagnosis of PND, any associated malignancy, and treatment. Case notes were reviewed and follow up data obtained where possible one year after notification. RESULTS: A total of 63 patients (48 females, 15 males) were identified, 48 through the BNSU and 15 through direct referral. Of these 52 were diagnosed as having definite PND, 10 probable PND, and 1 possible PND. The median age of onset of PND was 66 years (range 30-80 years) and only 7 patients (11%) were less than 50 years at presentation. In 53 patients (84%) the PND preceded the diagnosis of cancer. Paraneoplastic sensory neuronopathy, paraneoplastic encephalomyelitis, and paraneoplastic cerebellar degeneration (PCD) were the most common syndromes reported. The benefit of magnetic resonance imaging in the diagnosis of the disease was limited, while fluorodeoxyglucose positron emission tomography was shown to be useful for the detection of an occult malignancy in 10 out of 14 patients. Antineuronal antibodies were positive in 44/57 (77%) of cases. The following tumours were diagnosed: small cell lung cancer (30%), breast cancer (14%), ovarian cancer (8%), non-small cell lung cancer (8%), Hodgkin's lymphoma (6%), other (16%). With the exception of PCD associated with mesothelioma all other tumours diagnosed in these patients had been previously documented as being associated with PND. Only treatment of the tumour was found to be associated with a stable or improved neurological outcome at last follow up (Fisher's exact test = 4.7, p<0.03). Median survival time was 43 months (95% CI 28 to 57) from onset of neurological disease as calculated using the Kaplan-Meier survival analysis. CONCLUSIONS: PND has a striking female preponderance usually affecting patients in their sixth decade and above. The median survival in our study was 43 months. The majority of patients with PND are not known to have cancer at the time of diagnosis. Our study confirms the importance of diagnosing and treating the underlying tumour.     

Hearing impairment is common in various phenotypes of the mitochondrial DNA A3243G mutation.

OBJECTIVE: To determine whether there are common symptoms within different phenotypes of the mitochondrial DNA A3243G mutation. DESIGN: A series of 52 adults with mitochondrial encephalomyopathies and their symptomatic relatives were screened for the A3243G mutation using restriction enzyme analysis. In addition to clinical examination, patients with the mutation underwent audiometry. RESULTS: The A3243G mutation was identified in 16 patients (10 index patients and 6 symptomatic relatives). Six of these patients presented with strokelike episodes and met the classical criteria of MELAS syndrome (mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes), and one had MELAS/MERRF (myoclonic epilepsy with ragged-red fibers) overlap syndrome. Two patients presented with strokelike episodes but did not meet the classical criteria of MELAS. Predominant features of the 8 other patients were myopathy with hearing loss and diabetes mellitus (n = 1), chronic progressive external ophthalmoplegia (n = 1), diabetes mellitus with hearing loss (n = 1), painful muscle stiffness with hearing loss (n = 1), cardiomyopathy (n = 1), diabetes mellitus (n = 1), and hearing loss (n = 2). In 11 of 16 patients, hearing impairment was obvious on clinical examination. Furthermore, all 5 patients with normal hearing on clinical examination showed subclinical hearing loss; in 4, hearing loss was more pronounced than age-related hearing impairment and in 1, hearing loss can be age related as well. CONCLUSIONS: A variety of phenotypes represent the variable multisystemic involvement of the A3243G mutation. Less than half of the patients presented with MELAS. Hearing impairment, the most common symptom, was clinically or subclinically relevant in 15 (94%) of 16 patients.     

Malignant migraine: the syndrome of prolonged classical migraine, epilepsia partialis continua, and repeated strokes; a clinically characteristic disorder probably due to mitochondrial encephalopathy

We present ten patients with classical or common migraine of increasing severity accompanied by seizures of multiple patterns and increasing severity leading to episodes of epilepsia partialis continua. Long lasting deficits associated with hypodense lesions on CT and abnormal signals on MRI, then developed. Cortical blindness, cortical deafness and dementia were common. Five of the patients died in 1-10 years. Some of these patients had markers of mitochondrial disease (ragged red fibers and serum lactate elevation) and others with the same clinical picture did not. This group of patients indicates that mitochondrial encephalopathy may exist without evidence of myopathy, that the clinical syndrome is characteristic and that it should suggest the diagnosis even in the absence of muscular abnormalities.     

Clinical features of frontotemporal dementia due to the intronic tau 10(+16) mutation

OBJECTIVE: To describe the clinical features of nine British families with neuropathologically verified frontotemporal dementia (FTD) due to the intronic tau exon 10(+16) mutation. METHODS: Retrospective chart reviews of family members with FTD belonging to nine tau 10(+16) mutation pedigrees in whom neuropathologic examination had been carried out. APOE genotype was determined for those patients for whom DNA was available. RESULTS: The median age at onset was 50 years (range 37 to 59 years; n = 30). The median age at death was 61 years (range 42 to 72 years; n = 33). The median duration of the disease was 11 years (range 3 to 22 years; n = 25) for those who have died and is 17 years (range 15 to 23 years; n = 3) for those living. The most common presenting symptom was disinhibition (n = 23). A minority presented with frontal dysexecutive symptoms, apathy, impairment of episodic memory, or depression. All of these patients subsequently developed personality and behavioral change. Memory impairment, language deficits, ritualistic behavior, hyperphagia, and hyperorality were frequent symptoms. Parkinsonism, neuroleptic sensitivity, or primitive reflexes were present in half of the patients, where these data were available. The clinical features of ALS were absent. Neuropathologic examination of 12 patients demonstrated the hallmark tau-positive neuronal and glial inclusions. APOE genotype did not account for the considerable variation in age at onset, age at death, duration of disease, or severity of estimated brain atrophy. CONCLUSIONS: All cases fulfilled the clinical criteria for a diagnosis of FTD. Despite similar clinical phenotypes, there was considerable variation in age at onset and duration of disease both between and within families, suggesting the presence of an effect due to other genetic or environmental factors.     

Human mitochondrial transfer RNAs: role of pathogenic mutation in disease

The human mitochondrial genome encodes 13 proteins. All are subunits of the respiratory chain complexes involved in energy metabolism. These proteins are translated by a set of 22 mitochondrial transfer RNAs (tRNAs) that are required for codon reading. Human mitochondrial tRNA genes are hotspots for pathogenic mutations and have attracted interest over the last two decades with the rapid discovery of point mutations associated with a vast array of neuromuscular disorders and diverse clinical phenotypes. In this review, we use a scoring system to determine the pathogenicity of the mutations and summarize the current knowledge of structure-function relationships of these mutant tRNAs. We also provide readers with an overview of a large variety of mechanisms by which mutations may affect the mitochondrial translation machinery and cause disease.     

MERRF: a model disease for understanding the principles of mitochondrial genetics

The principles of mitochondrial genetics have evolved over the past 20 years. Careful identification of large pedigrees that were consistent with maternal inheritance has permitted detailed clinical and genetic investigations. Myoclonic epilepsy and ragged-red fiber (MERRF) disease has been a model disease for the application of these principles. MERRF is caused by an A to G mutation of the mitochondrial tRNA(Lys) at position 8344. The mutation is maternally inherited and heteroplasmic. Disease manifestations are dependent on replicative segregation of mutant and wild type mitochondrial DNAs and on the threshold effect. Characterization of the clinical, physiological, biochemical, and genetic manifestations of this disease has provided a better understanding of how to diagnose and manage oxidative phosphorylation diseases which are caused by mutations in the mitochondrial DNA.     

Difference in mitochondrial DNA copy number in peripheral blood cells between probands with autism spectrum disorders and their unaffected siblings

Objectives: Several reports suggest that mitochondrial dysfunction is involved in the pathophysiology of autism spectrum disorders (ASD). Therefore, mitochondrial DNA (mtDNA) copy number, a common biomarker for mitochondrial dysfunction, might be associated with ASD phenotypes.

Methods: Relative mtDNA copy number in the peripheral blood cells of 100 Korean ASD patients and their unaffected sib-pairs was measured by quantitative polymerase chain reaction (qPCR).

Results: ASD patients had significantly higher relative mtDNA copy numbers than their unaffected sibs (P?=?.042). In addition, there were statistically significant correlations between mtDNA copy number and clinical phenotypes for language and communication in ASD.

Conclusions: Our findings suggest that mitochondrial dysfunction and elevated mtDNA copy number may be a biological subtype of ASD that is related to the phenotype for communication.     

Cerebellar and parkinsonian phenotypes in multiple system atrophy: similarities,differences and survival

Multiple system atrophy (MSA) is a neurodegenerative disease with two motor phenotypes: parkinsonian (MSA-P) and cerebellar (MSA-C). To elucidate whether in addition to the motor abnormalities there are other significant differences between these phenotypes, we performed a retrospective review of 100 patients (61 males, 39 females) with a diagnosis of possible (12 %), or probable (88 %) MSA. Four patients eventually had post-mortem confirmation (i.e., definite MSA). Sixty percent were classified as having MSA-P and 40 % as MSA-C. MSA-C and MSA-P patients had similar male prevalence (60 %), age of onset (56 ± 9 years), and frequency of OH (69 %). Brain MRI abnormalities were more frequent in MSA-C patients (p < 0.001). Mean survival was 8 ± 3 years for MSA-C and 9 ± 4 years for MSA-P patients (p = 0.22). Disease onset before 55 years predicted longer survival in both phenotypes. Initial autonomic involvement did not influence survival. We conclude that patients with both motor phenotypes have mostly similar survivals and demographic distributions. The differences here identified could help counseling of patients with MSA.     

Incidence of carpal tunnel syndrome in adult patients with mitochondrial disease

Symmetrical polyneuropathy is a common feature of mitochondrial disease. Both axonal and demyelinating types are described, with Schwann cell abnormalities demonstrated on nerve biopsy. Some authors have also suggested an increased incidence of entrapment neuropathy. We identified 738 adult patients with proven mitochondrial disease seen in our centre in the past 25 years. One‐hundred sixty seven of these patients had undergone nerve conduction studies as part of their routine clinical care, and the results of these studies were reviewed. We found an incidence rate of carpal tunnel syndrome (CTS) of 50.7 per 100,000 person‐years; 32.5 per 100,000 person‐years for men and 65.3 per 100,000 person‐years for women. One other patient had evidence of ulnar neuropathy at the elbow. The incidence of CTS in mitochondrial disease is similar to published rates for the UK general population. We found no evidence that mitochondrial disease per se increases the risk of entrapment neuropathy. We suggest that the pathophysiological mechanisms for the development of polyneuropathy in mitochondrial disease are quite distinct from the pathophysiology of CTS. Furthermore, it is essential that patients with mitochondrial disease who present with upper limb paraesthesia be referred for neurophysiological testing, so that treatable CTS is not missed.     

Phenotyping mitochondrial DNA-related diseases in childhood: A cohort study of 150 patients

Background and purpose

Mitochondrial diseases (MDs) are heterogeneous disorders caused by mutations in nuclear DNA (nDNA) or mitochondrial DNA (mtDNA) associated with specific syndromes. However, especially in childhood, patients often display heterogeneity. Several reports on the biochemical and molecular profiles in children have been published, but studies tend not to differentiate between mtDNA- and nDNA-associated diseases, and focus is often on a specific phenotype. Thus, large cohort studies specifically focusing on mtDNA defects in the pediatric population are lacking.

Methods

We reviewed the clinical, metabolic, biochemical, and neuroimaging data of 150 patients with MDs due to mtDNA alterations collected at our neurological institute over the past 20 years.

Results

mtDNA impairment is less frequent than nDNA impairment in pediatric MDs. Ocular involvement is extremely frequent in our cohort, as is classical Leber hereditary optic neuropathy, especially with onset before 12 years of age. Extraneurological manifestations and isolated myopathy appear to be rare, unlike adult phenotypes. Deep gray matter involvement, early disease onset, and specific phenotypes, such as Pearson syndrome and Leigh syndrome, represent unfavorable prognostic factors. Phenotypes related to single large scale mtDNA deletions appear to be very frequent in the pediatric population. Furthermore, we report for the first time an mtDNA pathogenic variant associated with cavitating leukodystrophy.

Conclusions

We report on a large cohort of pediatric patients with mtDNA defects, adding new data on the phenotypical characterization of mtDNA defects and suggestions for diagnostic workup and therapeutic approach.     

Epileptic seizures in infants and children with mitochondrial diseases

The purpose of this study is to describe the characteristics of epileptic seizures in infants and children with mitochondrial diseases. From 1984 to December 2010, data from 46 of 76 patients diagnosed as having mitochondrial diseases with epileptic seizures were reviewed. Age at seizure onset, epileptic phenotypes, electroencephalogram findings, magnetic resonance imaging features, and treatment outcome in patients with syndromic or nonsyndromic mitochondrial diseases were analyzed. Thirty (65%) of 46 patients manifested seizures before the age of 1 year; 43% had Leigh syndrome and 53% had nonsyndromic mitochondrial diseases. Twenty-eight (61%) of 46 patients exhibited seizures as the manifesting complaint. Nineteen (68%) of 28 patients had nonsyndromic mitochondrial diseases. The most frequently observed electroencephalogram finding was background slow activity (28/46; 61%) in both groups. The most common cortical abnormality relevant to clinical seizures was diffuse brain atrophy on the brain magnetic resonance imaging (26/45; 58%), which was commonly observed in patients with nonsyndromic mitochondrial diseases (16/26; 62%). Despite treatment, 49% of patients experienced less than 50% seizure reduction rate, 77% of whom had nonsyndromic mitochondrial diseases. Leigh syndrome and nonsyndromic mitochondrial diseases often manifest as infantile seizures. Epileptic seizure as the initial complaint, diffuse brain atrophy, and refractory epilepsy were more common in patients with nonsyndromic mitochondrial diseases.     

The puzzle of multiple sclerosis: gray matter finds its place

The way we think of multiple sclerosis (MS) pathology has significantly changed over the last 10 years. Several studies clearly indicate that MS has to be considered a gray and white matter disease, where gray matter pathology probably plays a relevant role in determining physical and cognitive disability. The reviewed article presents new cross-sectional data on gray matter and white matter volumes across different MS phenotypes in a very large group of MS patients. In their study, the authors confirm an early and substantial deterioration of gray matter in MS and the evidence of a primary role of gray matter atrophy in the progression of clinical and cognitive disability. Another preliminary exciting step has therefore been taken toward the comprehension of the MS puzzle.     

Time of loss of employment in Parkinson's disease.

We examined time to loss of employment in two U.K.-based studies of 151 and 308 patients with Parkinson's disease (PD) with onset age before 65 years. Fifty-two percent and 57% of patients had retired early due to PD, 18% and 5% of patients were unemployed, and 8% and 11% were part-time-employed. Mean age of retirement was 55.8 years compared to an average retirement age of 62 years in the U.K. population. Mean time to loss of employment was 4.9 years, ranging from a mean of 6.7 years in those with onset before age 45 to 1.7 years in those with onset after age 56, but the range was large (0-17 years). After censoring for those still working and those retiring at a normal retirement age, survival analysis revealed that 46% had stopped working after a disease duration of 5 years and 82% after 10 years with a median survival to loss of employment of 6.0 (95% CI: 5.4-6.6) years. Age of onset correlated negatively with time to loss of employment (r = -0.6; P < 0.001). There were no differences between sexes, rural vs. urban living, types of work, those living alone or with a partner, and those with and without children in their household. We conclude that Parkinson's disease leads to loss of employment on average within less than 10 years of disease onset. However, the variability of time to loss of employment is large, indicating that other factors than onset age and disease duration influence loss of patients' employment.