Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes

WikiDoc Resources for Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes
Articles
Most recent articles on Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes Most cited articles on Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes Review articles on Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes Articles on Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes in N Eng J Med, Lancet, BMJ
Media
Powerpoint slides on Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes Images of Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes Photos of Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes Podcasts & MP3s on Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes Videos on Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes
Evidence Based Medicine
Cochrane Collaboration on Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes Bandolier on Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes TRIP on Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes
Clinical Trials
Ongoing Trials on Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes at Clinical Trials.gov Trial results on Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes Clinical Trials on Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes at Google
Guidelines / Policies / Govt
US National Guidelines Clearinghouse on Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes NICE Guidance on Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes NHS PRODIGY Guidance FDA on Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes CDC on Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes
Books
Books on Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes
News
Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes in the news Be alerted to news on Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes News trends on Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes
Commentary
Blogs on Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes
Definitions
Definitions of Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes
Patient Resources / Community
Patient resources on Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes Discussion groups on Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes Patient Handouts on Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes Directions to Hospitals Treating Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes Risk calculators and risk factors for Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes
Healthcare Provider Resources
Symptoms of Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes Causes & Risk Factors for Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes Diagnostic studies for Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes Treatment of Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes
Continuing Medical Education (CME)
CME Programs on Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes
International
Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes en Espanol Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes en Francais
Business
Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes in the Marketplace Patents on Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes
Experimental / Informatics
List of terms related to Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief:

Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes
OMIM	540000
DiseasesDB	8254
MeSH	D017241

Overview

Mitochondrial myopathy, encephalopathy, lactic acidosis, stroke-like episodes, abbreviated to MELAS is one of the family of mitochondrial cytopathies, which also include MERRF, and Leber's Hereditary Optic Atrophy. A feature of these diseases is that they are caused by defects in the mitochondrial genome which is inherited purely from the female parent. The disease can manifest in both sexes.

Pathophysiology

Genetics

Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes is a condition related to changes in mitochondrial DNA. Mutations in the MT-ND1, MT-ND5, MT-TH, MT-TL1, and MT-TV genes cause mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes. The genes associated with MELAS are contained in mitochondrial DNA. Some of the genes related to MELAS provide instructions for making proteins involved in normal mitochondrial function. These proteins are part of a large enzyme complex in mitochondria that helps convert oxygen and simple sugars to energy. Other genes associated with this disorder provide instructions for making molecules called transfer RNAs (tRNAs), which are chemical cousins of DNA. These molecules help assemble protein building blocks called amino acids into full-length, functioning proteins within mitochondria.

Mutations in a particular transfer RNA gene, MT-TL1, cause more than 80 percent of all cases of MELAS. These mutations impair the ability of mitochondria to make proteins, use oxygen, and produce energy. Researchers have not determined how changes in mitochondrial DNA lead to the specific signs and symptoms of MELAS. They continue to investigate the effects of mitochondrial gene mutations in different tissues, particularly in the brain.

This condition is inherited in a mitochondrial pattern, which is also known as maternal inheritance. This pattern of inheritance applies to genes contained in mitochondrial DNA. Because egg cells, but not sperm cells, contribute mitochondria to the developing embryo, only females pass mitochondrial conditions to their children. Mitochondrial disorders can appear in every generation of a family and can affect both males and females, but fathers do not pass mitochondrial traits to their children. In most cases, people with MELAS inherit an altered mitochondrial gene from their mother. Less commonly, the disorder results from a new mutation in a mitochondrial gene and occurs in people with no family history of MELAS.

Epidemiology and Demographics

MELAS is recognized as one of the most common mitochondrial disorders, affecting approximately 1 in every 4000 individuals. While both sexes are equally susceptible to developing the condition, only females can transmit MELAS due to the unique nature of mitochondrial inheritance. Mitochondria are carried within the tails of sperm cells, which are shed outside the zygote during fertilization and are therefore not transmitted, resulting in this gender-specific inheritance pattern. Notably, there is no discernible racial preference associated with MELAS.

Natural History, Complications and Prognosis

Prognosis

There is no known treatment for the underlying disease, which is progressive and fatal. Patients are managed according to what areas of the body are affected at a particular time. Antioxidants and vitamins have been used, but there have been no consistent successes reported.

Diagnosis

History and Symptoms

MELAS is a condition that affects many of the body's systems, particularly the brain and nervous system (encephalo-) and muscles (myopathy). In most cases, the signs and symptoms of this disorder appear in childhood following a period of normal development. Early symptoms may include

• Muscle weakness
• Muscle pain
• Recurrent headaches
• Loss of appetite
• Vomiting
• Seizures
• Abdominal pain
• Extreme tiredness (fatigue)
• Difficulty breathing

Physical Examination

Eye

• Vision abnormalities

Ear

• Hearing loss

Extremeties

• Myoclonus

Neurologic

• Stroke-like episodes beginning before age 40
• Temporary muscle weakness on one side of the body (hemiparesis)
• Altered consciousness
• Ataxia
• Seizures
• Dementia

Laboratory Findings

Laboratory workup involves assessing serum pyruvic acid, serum lactic acid, cerebrospinal fluid (CSF) pyruvic acid, and CSF lactic acid. An elevation in lactic acid levels, especially during an acute stroke-like episode, is a frequent initial finding. However, lactic acids may be normal in some people and an increased CSF lactic acid level has been shown to be a more reliable indicator of disease. However, systemic metabolic acidosis does not occur.