Mitochondrial encephalomyopathy with lactic acidosis and stroke (MELAS)

Department of Neurology, The David Geffen School of Medicine at UCLA, Los Angeles, CA, USA.
Reviews in neurological diseases 02/2005; 2(1):30-4.
Source: PubMed


Mitochondrial disorders are an uncommon, but important, cause of stroke-like clinical and imaging presentations in individuals under the age of 45 years. We present a 31-year-old man with a 4-year history of migraine-like headaches, type 2 diabetes mellitus, seizures, and hearing loss. Magnetic resonance imaging revealed multiple hyperintensities on T2 and fluid-attenuated inversion recovery sequences. An exhaustive work-up for vasculitis including brain biopsy was performed. Mitochondrial DNA testing revealed the A3243G substitution associated with the mitochondrial encephalomyopathy with lactic acidosis and stroke syndrome. In this case review we briefly discuss the signs and symptoms, frequency, pathophysiology, and prognosis of this disorder.

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    ABSTRACT: The central nervous system (CNS) is, after the peripheral nervous system, the second most frequently affected organ in mitochondrial disorders (MCDs). CNS involvement in MCDs is clinically heterogeneous, manifesting as epilepsy, stroke-like episodes, migraine, ataxia, spasticity, extrapyramidal abnormalities, bulbar dysfunction, psychiatric abnormalities, neuropsychological deficits, or hypophysial abnormalities. CNS involvement is found in syndromic and non-syndromic MCDs. Syndromic MCDs with CNS involvement include mitochondrial encephalomyopathy, lactacidosis, stroke-like episodes syndrome, myoclonic epilepsy and ragged red fibers syndrome, mitochondrial neuro-gastrointestinal encephalomyopathy syndrome, neurogenic muscle weakness, ataxia, and retinitis pigmentosa syndrome, mitochondrial depletion syndrome, Kearns-Sayre syndrome, and Leigh syndrome, Leber's hereditary optic neuropathy, Friedreich's ataxia, and multiple systemic lipomatosis. As CNS involvement is often subclinical, the CNS including the spinal cord should be investigated even in the absence of overt clinical CNS manifestations. CNS investigations comprise the history, clinical neurological examination, neuropsychological tests, electroencephalogram, cerebral computed tomography scan, and magnetic resonance imaging. A spinal tap is indicated if there is episodic or permanent impaired consciousness or in case of cognitive decline. More sophisticated methods are required if the CNS is solely affected. Treatment of CNS manifestations in MCDs is symptomatic and focused on epilepsy, headache, lactacidosis, impaired consciousness, confusion, spasticity, extrapyramidal abnormalities, or depression. Valproate, carbamazepine, corticosteroids, acetyl salicylic acid, local and volatile anesthetics should be applied with caution. Avoiding certain drugs is often more beneficial than application of established, apparently indicated drugs.
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    ABSTRACT: During the last decade, there has been a progressive accumulation of reports that connect the identification of specific mitochondrial tRNA gene mutations to severe disorders in human. As a result, mitochondrial tRNA genes and their products have emerged as novel and essential molecular markers for wide biochemical and genetic screenings among different human populations. So far, 139 pathogenic and 243 polymorphic mt tRNA mutations have been described and they have become the foreground of numerous case reports. Given the complexity of mitochondrial genetics and biochemistry, the clinical manifestations of mitochondrial disorders are extremely heterogeneous. They range from lesions of single tissues or structures to more severe impairments including myopathies, encephalomyopathies, cardiomyopathies, or complex multisystem syndromes. Moreover, the exact mechanisms by which biochemical cascades can be dramatically affected by mitochondrial tRNA mutations still remain uncharacterized. However and regardless of the vast amount of information that daily emerges, only few efforts have been carried out to systematically record all the mitochondrial tRNA-associated pathogenic mutations or polymorphisms. In this report, we summarize all the clinical phenotypes associated with mitochondrial tRNA pathogenic mutations that have been reported so far. In a next step we describe in detail all the pathogenic and polymorphic mutations that have been recorded so far and we categorize them per tRNA species and per associated disease. Finally, we discuss the impact of the frequency of mitochondrial tRNA mutations in general population surveys and we preview any relevant implications on the essential functional integrity of mitochondrial biochemical pathways.
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