Mitochondrial encephalomyopathy lactic acidosis and stroke-like episodes

How is mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) inherited?

MELAS is caused by mutations in mitochondrial DNA (mtDNA) and is therefore transmitted by maternal inheritance (also called mitochondrial inheritance). This type of inheritance applies to all conditions caused by genes in mtDNA. Mitochondria are structures in each cell that turn molecules into energy, and each contain a small amount of DNA. Only egg cells (not sperm cells) contribute mitochondria to offspring, so only females can pass on mitochondrial mutations to their children. Conditions resulting from mutations in mtDNA can appear in every generation of a family and can affect both males and females. In most cases, people with MELAS inherit an altered mitochondrial gene from their mother. Less commonly, the condition results from a new mutation in a mitochondrial gene and occurs in an individual with no history of MELAS in the family.

Last updated on 05-01-20

Is there a link between mitochondrial encephalomyopathy lactic acidosis and stroke-like episodes (MELAS) and a person who is not really strong?

As mentioned above, muscle weakness and extreme fatigue are common in this condition.

Last updated on 05-01-20

What is the chance that a sibling of an individual with mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) will be affected?

The risk to the siblings of an individual affected with MELAS depends on the genetic status of their mother. If their mother has the mtDNA mutation, all of the siblings of the affected individual will inherit the disease-causing mtDNA mutation; however, the siblings may or may not have symptoms. One study reported that women with higher levels of the mutated mtDNA in their blood have a greater likelihood of having affected offspring (i.e. children with symptoms of the condition).

Unfortunately, it is not possible to predict whether an individual with an mtDNA mutation will have specific symptoms. The possible effects of an mtDNA mutation depend on a combination of factors, including the severity of the mutation, the percentage of mitochondria that have the mutation, and the organs and tissues in which the mutated mitochondria are located. Different family members often inherit different percentages of mutated mtDNA and therefore can have a wide range of clinical symptoms. Test results of at-risk family members who don't currently have symptoms are very hard to interpret.

Individuals concerned about specific risks to themselves or family members should speak with a genetics professional.

Last updated on 05-01-20

Name: United Mitochondrial Disease Foundation 8085 Saltsburg Road, Suite 201
Pittsburgh, PA, 15239 , United States
Phone: +1-412-793-8077 Toll Free: 1-888-317-8633 Fax : +1-412-793-6477 Email: Url:
Name: The Mitochondria Research and Medicine Society PO Box 55322
Birmingham, AL,
Phone: 716-907-4349 Fax : 716-845-1047 Email: Url:
Name: MitoAction PO Box 51474
Boston, MA, 02205, United States
Phone: 1-888-MITO-411 (648-6411) for support line Toll Free: 1-888-648-6228 Email: Url:
Name: Australian Mitochondrial Disease Foundation AMDF Suite 3 21 Mary Street
Surry Hills New South Wales 2010
Phone: 1300 977 180 Email: Url:

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