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Query: UMLS:C0085584 (encephalopathy)
 18,178 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Since the first identification in 1988 of pathogenic mitochondrial DNA (mtDNA) mutations, the mitochondrial diseases have emerged as a major clinical entity. The most striking feature of these disorders is their marked heterogeneity, which extends to their clinical, biochemical, and genetic characteristics. The major mitochondrial encephalomyopathies include MELAS (mitochondrial encephalopathy with lactic acidosis and stroke-like episodes), MERRF (myoclonic epilepsy with ragged red fibers), KSS/CPEO (Kearns-Sayre syndrome/chronic progressive external ophthalmoplegia), and NARP/MILS (neuropathy, ataxia, and retinitis pigmentosum/maternally inherited Leigh syndrome) and they typically present highly variable multisystem defects that usually involve abnormalities of skeletal muscle and/or the CNS. The primary emphasis here is to review recent investigations of these mitochondrial diseases from the standpoint of how the complexities of mitochondrial genetics and biogenesis might determine their varied features. In addition, the mitochondrial encephalomyopathies are compared and contrasted to Leber hereditary optic neuropathy, a mitochondrial disease in which the pathogenic mtDNA mutations produce a more uniform and focal neuropathology. All of these disorders involve, at some level, a mitochondrial respiratory chain dysfunction. Because mitochondrial genetics differs so strikingly from the Mendelian inheritance of chromosomes, recent research on the origin and subsequent segregation and transmission of mtDNA mutations is reviewed.
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PMID:Human mitochondrial diseases: answering questions and questioning answers. 977 Feb 97

Congenital disorders of glycosylation (CDG) and mitochondrial diseases are multisystem disorders with clinical characteristics that may overlap. We present four patients with CDG whose phenotypes suggested the diagnosis of a mitochondrial disease. Patients 1 and 2 are siblings with hemiplegic headache, stroke-like episodes, lactic acidaemia and history of maternal migraine; their initial clinical diagnosis was MELAS syndrome (mitochondrial encephalopathy, lactic acidosis and stroke-like episodes). Patient 3 suffers from ataxia, neuropathy, ophtalmoplegia and retinitis pigmentosa suggestive of NARP (neuropathy, ataxia, and retinitis pigmentosa) syndrome. Patient 4 presented with neurological regression mimicking Leigh disease, with ptosis, myoclonus, ataxia and brainstem and cerebellar atrophy. Screening for mitochondrial disease including enzyme and mtDNA investigations on muscle biopsy were performed on Patients 1, 2 and 4 with normal results. However, evidence for a glycosylation disorder was substantiated by an increased carbohydrate deficient transferrin (CDT). The isoelectric focussing pattern of serum sialotransferrin was typical of CDG type I in Patients 1, 2 and 3 and was shifted towards the less sialylated bands in case 4. A deficiency of phosphomanomutase (PMM) confirmed the diagnosis of CDG-Ia in Patients 1, 2 and 3, who are compound heterozygous for mutations R141H/T237M (Patients 1 and 2) and R141H/P113L (Patient 3). In Patient 4, PMM activity was normal, and further enzymatic and molecular studies are underway. As the search for the primary defect in mitochondrial diseases is often unsuccessful, the pool of mitochondrial patients that remain without definite diagnosis might include CDG cases. Routine screening for CDG may avoid precocious invasive investigations.
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PMID:Congenital disorders of glycosylation (CDG) may be underdiagnosed when mimicking mitochondrial disease. 1158 67

This paper discusses the pros and cons of introducing PGD for mitochondrial DNA (mtDNA) disorders such as NARP (Neurogenic muscle weakness, Ataxia, Retinis Pigmentosa)/Leigh, MELAS (Mitochondrial myopathy, Encephalopathy, Lactic acidosis, and Stroke-like episodes), private mtDNA mutations and LHON (Leber Hereditary Optic Neuropathy). Although there is little experience with PGD for mtDNA disorders, it is reasonable to assume that in many cases, the best one can achieve is the selection of the 'least' affected embryos for transfer. So instead of 'promising' parents a healthy child, PGD in these cases can only aim at reducing reproductive risk. From an ethical point of view, this raises challenging questions about parental and medical responsibilities. The main argument in favour of PGD is that it offers couples at risk the opportunity of reducing their chances of having a severely affected child. Potential objections are manifold, but we conclude that none of them supplies convincing moral arguments to regard risk-reducing PGD as unacceptable. Nevertheless, introducing this new application of PGD in clinical practice will raise further complex issues of determining conditions for its responsible use.
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PMID:PGD to reduce reproductive risk: the case of mitochondrial DNA disorders. 1866 74

Mitochondrial diseases associated with mutations within mitochondrial genome are a subgroup of metabolic disorders since their common consequence is reduced metabolic efficiency caused by impaired oxidative phophorylation and shortage of ATP. Although the vast majority of mitochondrial proteins (approximately 1500) is encoded by nuclear genome, mtDNA encodes 11 subunits of respiratory chain complexes, 2 subunits of ATP synthase, 22 tRNAs and 2 rRNAs. Up to now, more than 250 pathogenic mutations have been described within mtDNA. The most common are point mutations in genes encoding mitochondrial tRNAs such as 3243A-->G and 8344T-->G that cause, respectively, MELAS (mitochondrial encephalopathy, lactic acidosis and stroke-like episodes) or MIDD (maternally-inherited diabetes and deafness) and MERRF (myoclonic epilepsy with ragged red fibres) syndromes. There have been also found mutations in genes encoding subunits of ATP synthase such as 8993T-->G substitution associated with NARP (neuropathy, ataxia and retinitis pigmentosa) syndrome. It is worth to note that mitochondrial dysfunction can also be caused by mutations within nuclear genes coding for mitochondrial proteins.
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PMID:[Diseases caused by mutations in mitochondrial DNA]. 2191 24

Mitochondrial disorders are clinically and genetically heterogeneous. There are a set of recurrent point mutations in the mitochondrial DNA (mtDNA) that are responsible for common mitochondrial diseases, including MELAS (mitochondrial encephalopathy, lactic acidosis, stroke-like episodes), MERRF (myoclonic epilepsy and ragged red fibers), LHON (Leber's hereditary optic neuropathy), NARP (neuropathy, ataxia, retinitis pigmentosa), and Leigh syndrome. Most of the pathogenic mtDNA point mutations are present in the heteroplasmic state, meaning that the wild-type and mutant-containing mtDNA molecules are coexisting. Clinical heterogeneity may be due to the degree of mutant load (heteroplasmy) and distribution of heteroplasmic mutations in affected tissues. Additionally, Kearns-Sayre syndrome and Pearson syndrome are caused by large mtDNA deletions. In this chapter, we describe a multiplex PCR/allele-specific oligonucleotide (ASO) hybridization method for the screening of 13 common point mutations. This method allows the detection of low percentage of mutant heteroplasmy. In addition, a nonradioactive Southern blot hybridization protocol for the analysis of mtDNA large deletions is also described.
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PMID:Analysis of common mitochondrial DNA mutations by allele-specific oligonucleotide and Southern blot hybridization. 2221 54

Though inherited mitochondrial disorders (MIDs) are most well known for their syndromic forms, for which widely known acronyms (MELAS, MERRF, NARP, LHON etc.) have been coined, the vast majority of inherited MIDs presents in a non-syndromic form. Since MIDs are most frequently multisystem disorders already at onset or during the disease course, a MID should be suspected if there is a combination of neurological and non-neurological abnormalities. Neurological abnormalities occurring as a part of a MID include stroke-like episodes, epilepsy, migraine-like headache, movement disorders, cerebellar ataxia, visual impairment, encephalopathy, cognitive impairment, dementia, psychosis, hypopituitarism, aneurysms, or peripheral nervous system disease, such as myopathy, neuropathy, or neuronopathy. Non-neurological manifestations concern the ears, the endocrine organs, the heart, the gastrointestinal tract, the kidneys, the bone marrow, and the skin. Whenever there is an unexplained combination of neurological and non-neurological disease in a patient or kindred, a MID should be suspected and appropriate diagnostic measures initiated. Genetic testing should be guided by the phenotype, the biopsy findings, and the biochemical results.
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PMID:Inherited mitochondrial disorders. 2239 23