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Mitochondrial encephalomyopathy lactic acidosis and stroke-like episodes
- Other Names:
MELAS; MELAS syndromeMELAS; MELAS syndrome
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Disease at a Glance
Summary
Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) affects many parts of the body, particularly the brain and nervous system (encephalo-) and muscles (myopathy). Symptoms typically begin in childhood and may include muscle weakness and pain, recurrent headaches, loss of appetite, vomiting, and seizures. People with MELAS can also have a buildup of lactic acid in their bodies that can lead to vomiting, abdominal pain, fatigue, muscle weakness, and difficulty breathing. The genes associated with MELAS are located in mitochondrial DNA and therefore follow a maternal inheritance pattern (also called mitochondrial inheritance). MELAS can be inherited from the mother only, because only females pass mitochondrial DNA to their children. In some cases, MELAS results from a new genetic change that was not inherited from a person's mother.
Estimated Number of People with this Disease
In the U.S., this disease is estimated to be less than
5,000
What Information Does GARD Have For This Disease?
Many rare diseases have limited information. Currently GARD is able to provide the following information for this disease:
*Data may be currently unavailable to GARD at this time.
When do symptoms of this disease begin?
The most common ages for symptoms of a disease to begin is called age of onset. Age of onset can vary for different diseases and may be used by a doctor to determine the diagnosis. For some diseases, symptoms may begin in a single age range or several age ranges. For other diseases, symptoms may begin any time during a person's life.
Prenatal
Before Birth
Newborn
Birth-4 weeks
Infant
1-23 months
Child Selected
2-11 years
Adolescent Selected
12-18 years
Adult Selected
19-65 years
Older Adult
65+ years
The common ages for symptoms to begin in this disease are shown above by the colored icon(s).
Symptoms
These symptoms may be different from person to person. Some people may have more symptoms than others and symptoms can range from mild to severe. This list does not include every symptom.
This disease might cause these symptoms:
This disease might cause these symptoms:
Nervous System
77 Symptoms
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Nervous System
The nervous system is made up of the brain, spinal cord, and nerves. Common symptoms of problems in the nervous system include trouble moving, speaking, swallowing, breathing, or learning. Problems with memory, senses, or mood may also occur. Nervous system diseases are usually diagnosed and treated by neurologists.
77 Symptoms
Causes
Genetic Disease
Mitochondrial encephalomyopathy lactic acidosis and stroke-like episodes is a genetic disease, which means that it is caused by one or more genes not working correctly.
Disease causing variants in the following gene(s) are known to cause this disease: COX1, COX2, ND1, ND4, ND5, ND6, TRNL1, TRNW, TRNS1, MT-TF
Questions:
What is a gene?
Genes are part of our DNA, the basic genetic material found in each of our body's cells. Cells are the building blocks of all living things and specialized cells form our body's organs and tissues. DNA is found in the nucleus of a cell and, in humans, is packaged into 23 pairs of chromosomes with the help of special proteins.
Each gene performs a different job in our cells. Some genes serve as the instructions to make proteins. Proteins are needed for the structure, function, and regulation of the body's cells, tissues, and organs. Some genes can turn other genes on or off. Others make RNA molecules that are involved in chemical reactions in the body.
Sources to Learn More: What is a gene? (MedlinePlus) ; What's a Gene? (NHGRI) ; What are proteins and what do they do? (MedlinePlus)Genes are part of our DNA, the basic genetic material found in each of our body's cells. Cells are the building blocks of all living things and specialized cells form our body's organs and tissues. DNA is found in the nucleus of a cell and, in humans, is packaged into 23 pairs of chromosomes with the help of special proteins.
Each gene performs a different job in our cells. Some genes serve as the instructions to make proteins. Proteins are needed for the structure, function, and regulation of the body's cells, tissues, and organs. Some genes can turn other genes on or off. Others make RNA molecules that are involved in chemical reactions in the body.
Sources to Learn More: What is a gene? (MedlinePlus) ; What's a Gene? (NHGRI) ; What are proteins and what do they do? (MedlinePlus)
Each gene performs a different job in our cells. Some genes serve as the instructions to make proteins. Proteins are needed for the structure, function, and regulation of the body's cells, tissues, and organs. Some genes can turn other genes on or off. Others make RNA molecules that are involved in chemical reactions in the body.
Sources to Learn More: What is a gene? (MedlinePlus) ; What's a Gene? (NHGRI) ; What are proteins and what do they do? (MedlinePlus)Genes are part of our DNA, the basic genetic material found in each of our body's cells. Cells are the building blocks of all living things and specialized cells form our body's organs and tissues. DNA is found in the nucleus of a cell and, in humans, is packaged into 23 pairs of chromosomes with the help of special proteins.
Each gene performs a different job in our cells. Some genes serve as the instructions to make proteins. Proteins are needed for the structure, function, and regulation of the body's cells, tissues, and organs. Some genes can turn other genes on or off. Others make RNA molecules that are involved in chemical reactions in the body.
Sources to Learn More: What is a gene? (MedlinePlus) ; What's a Gene? (NHGRI) ; What are proteins and what do they do? (MedlinePlus)
What is a genetic variant?
A genetic variant is a change in a gene's code or DNA sequence that causes the gene to be different than found in most people. A benign variant does not cause health problems or disease because the change does not affect how the gene works. A pathogenic variant does cause health problems or disease because the change does affect how the gene works. A pathogenic variant may also be called a mutation or a disease-causing variant.
Variants can result from DNA copying mistakes made during cell division or certain environmental exposures. Variants that occur in the egg or sperm (germline mutations) can be passed on to offspring, while variants that occur in other body cells (somatic mutations) are not passed on.
Sources to Learn More: What is a genetic variant and how do variants occur? (MedlinePlus); Definition of Variant (NCI); Mutation definition, illustration, and related terms (NHGRI)A genetic variant is a change in a gene's code or DNA sequence that causes the gene to be different than found in most people. A benign variant does not cause health problems or disease because the change does not affect how the gene works. A pathogenic variant does cause health problems or disease because the change does affect how the gene works. A pathogenic variant may also be called a mutation or a disease-causing variant.
Variants can result from DNA copying mistakes made during cell division or certain environmental exposures. Variants that occur in the egg or sperm (germline mutations) can be passed on to offspring, while variants that occur in other body cells (somatic mutations) are not passed on.
Sources to Learn More: What is a genetic variant and how do variants occur? (MedlinePlus); Definition of Variant (NCI); Mutation definition, illustration, and related terms (NHGRI)
Variants can result from DNA copying mistakes made during cell division or certain environmental exposures. Variants that occur in the egg or sperm (germline mutations) can be passed on to offspring, while variants that occur in other body cells (somatic mutations) are not passed on.
Sources to Learn More: What is a genetic variant and how do variants occur? (MedlinePlus); Definition of Variant (NCI); Mutation definition, illustration, and related terms (NHGRI)A genetic variant is a change in a gene's code or DNA sequence that causes the gene to be different than found in most people. A benign variant does not cause health problems or disease because the change does not affect how the gene works. A pathogenic variant does cause health problems or disease because the change does affect how the gene works. A pathogenic variant may also be called a mutation or a disease-causing variant.
Variants can result from DNA copying mistakes made during cell division or certain environmental exposures. Variants that occur in the egg or sperm (germline mutations) can be passed on to offspring, while variants that occur in other body cells (somatic mutations) are not passed on.
Sources to Learn More: What is a genetic variant and how do variants occur? (MedlinePlus); Definition of Variant (NCI); Mutation definition, illustration, and related terms (NHGRI)
What is a genetic disease?
A genetic disease is a disease caused by a change in part of a person's DNA. Genetic diseases may be caused by genetic changes in a single gene, in multiple genes, by a combination of genetic changes and environmental factors (multifactorial inheritance), or changes in chromosomes.
Genetic diseases may be caused by genetic changes that are inherited from the parents and are present at birth, like sickle cell disease. Other genetic diseases present at birth may be caused by random genetic changes that happen while the egg or the sperm is forming or soon after fertilization.
Some diseases, like many cancers, are caused by genetic changes that happen during a person's life. These are known as acquired or somatic cell genetic changes. Such genetic changes are not inherited from a parent, but happen either randomly or due to some environmental exposure (such as cigarette smoke).
Sources to Learn More: Genetic Disorders (MedlinePlus) ; Genetic Disorders (NHGRI)A genetic disease is a disease caused by a change in part of a person's DNA. Genetic diseases may be caused by genetic changes in a single gene, in multiple genes, by a combination of genetic changes and environmental factors (multifactorial inheritance), or changes in chromosomes.
Genetic diseases may be caused by genetic changes that are inherited from the parents and are present at birth, like sickle cell disease. Other genetic diseases present at birth may be caused by random genetic changes that happen while the egg or the sperm is forming or soon after fertilization.
Some diseases, like many cancers, are caused by genetic changes that happen during a person's life. These are known as acquired or somatic cell genetic changes. Such genetic changes are not inherited from a parent, but happen either randomly or due to some environmental exposure (such as cigarette smoke).
Sources to Learn More: Genetic Disorders (MedlinePlus) ; Genetic Disorders (NHGRI)
Genetic diseases may be caused by genetic changes that are inherited from the parents and are present at birth, like sickle cell disease. Other genetic diseases present at birth may be caused by random genetic changes that happen while the egg or the sperm is forming or soon after fertilization.
Some diseases, like many cancers, are caused by genetic changes that happen during a person's life. These are known as acquired or somatic cell genetic changes. Such genetic changes are not inherited from a parent, but happen either randomly or due to some environmental exposure (such as cigarette smoke).
Sources to Learn More: Genetic Disorders (MedlinePlus) ; Genetic Disorders (NHGRI)A genetic disease is a disease caused by a change in part of a person's DNA. Genetic diseases may be caused by genetic changes in a single gene, in multiple genes, by a combination of genetic changes and environmental factors (multifactorial inheritance), or changes in chromosomes.
Genetic diseases may be caused by genetic changes that are inherited from the parents and are present at birth, like sickle cell disease. Other genetic diseases present at birth may be caused by random genetic changes that happen while the egg or the sperm is forming or soon after fertilization.
Some diseases, like many cancers, are caused by genetic changes that happen during a person's life. These are known as acquired or somatic cell genetic changes. Such genetic changes are not inherited from a parent, but happen either randomly or due to some environmental exposure (such as cigarette smoke).
Sources to Learn More: Genetic Disorders (MedlinePlus) ; Genetic Disorders (NHGRI)
Inheritance
All individuals inherit two copies of most genes. The number of copies of a gene that need to have a disease-causing variant affects the way a disease is inherited. This disease is inherited in the following pattern(s):
Questions:
Mitochondrial inheritance
Mitochondria are structures in each cell that produce energy and each one contains a small amount of DNA. A mitochondrial disease occurs when a gene located in mitochondrial DNA has a disease causing (pathogenic) variant. Mutation is an older term that is still sometimes used to mean pathogenic variant.
Because only egg cells contribute mitochondria to the developing embryo, only women can pass on mitochondrial variants to their children. Diseases caused by pathogenic variants in mitochondrial DNA can appear in every generation of a family and in both men and women, but fathers do not pass these disorders to their daughters or sons.
If a child is the first person in a family with the mitochondrial disease, the pathogenic variant may have occurred by chance for the first time in the child's mitochondria (de novo).Mitochondria are structures in each cell that produce energy and each one contains a small amount of DNA. A mitochondrial disease occurs when a gene located in mitochondrial DNA has a disease causing (pathogenic) variant. Mutation is an older term that is still sometimes used to mean pathogenic variant.
Because only egg cells contribute mitochondria to the developing embryo, only women can pass on mitochondrial variants to their children. Diseases caused by pathogenic variants in mitochondrial DNA can appear in every generation of a family and in both men and women, but fathers do not pass these disorders to their daughters or sons.
If a child is the first person in a family with the mitochondrial disease, the pathogenic variant may have occurred by chance for the first time in the child's mitochondria (de novo).
Because only egg cells contribute mitochondria to the developing embryo, only women can pass on mitochondrial variants to their children. Diseases caused by pathogenic variants in mitochondrial DNA can appear in every generation of a family and in both men and women, but fathers do not pass these disorders to their daughters or sons.
If a child is the first person in a family with the mitochondrial disease, the pathogenic variant may have occurred by chance for the first time in the child's mitochondria (de novo).Mitochondria are structures in each cell that produce energy and each one contains a small amount of DNA. A mitochondrial disease occurs when a gene located in mitochondrial DNA has a disease causing (pathogenic) variant. Mutation is an older term that is still sometimes used to mean pathogenic variant.
Because only egg cells contribute mitochondria to the developing embryo, only women can pass on mitochondrial variants to their children. Diseases caused by pathogenic variants in mitochondrial DNA can appear in every generation of a family and in both men and women, but fathers do not pass these disorders to their daughters or sons.
If a child is the first person in a family with the mitochondrial disease, the pathogenic variant may have occurred by chance for the first time in the child's mitochondria (de novo).
Next Steps
Talking with the Medical Team
Good communication between the patient, family, and medical team can lead to an accurate diagnosis. In addition, health care decisions can be made together which improves the patient’s well-being and quality of life.
The National Library of Medicine's Unified Medical Language System (UMLS) is used to classify and organize diseases and disease categories.
Data from Orphanet and Human Phenotype Ontology (HPO) are used to provide information on a disease's symptoms, genes, inheritance, population estimates, and more.
National Academies of Sciences, Engineering, and Medicine. 2015. Improving Diagnosis in Health Care. Washington, DC: The National Academies Press.
U.S. Department of Health and Human Services, Office of Disease Prevention and Health Promotion. (2015). Health Literacy Online: A Guide for Simplifying the User Experience.
- Reference: Access aggregated data from Orphanet at Orphadata. Orphanet is an online database of rare diseases and orphan drugs. Copyright, INSERM 1997.
- Reference: Download data from HPO. Kohler S, Gargano M, Matentzoglu N, et al., The Human Phenotype Ontology in 2021, Nucleic Acids Research, Volume 49, Issue D1, 8 January 2021, Pages D1207–D1217.
- Reference: MedGen Data Downloads and FTP
- Reference: Data from the Newborn Screening Coding and Terminology Guide is available here. Downs SM, van Dyck PC, Rinaldo P, et al. Improving newborn screening laboratory test ordering and result reporting using health information exchange . J Am Med Inform Assoc. 2010 Jan-Feb;17(1):13-8.
National Academies of Sciences, Engineering, and Medicine. 2015. Improving Diagnosis in Health Care. Washington, DC: The National Academies Press.
U.S. Department of Health and Human Services, Office of Disease Prevention and Health Promotion. (2015). Health Literacy Online: A Guide for Simplifying the User Experience.
Last Updated: Nov. 8, 2021