MELAS

What is MELAS?
Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (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 and pain, recurrent headaches, loss of appetite, vomiting, and seizures. Most affected individuals experience stroke-like episodes beginning before age 40. These episodes often involve temporary muscle weakness on one side of the body (hemiparesis), altered consciousness, vision abnormalities, seizures, and severe headaches resembling migraines. Repeated stroke-like episodes can progressively damage the brain, leading to vision loss, problems with movement, and a loss of intellectual function (dementia).

Most people with MELAS have a buildup of lactic acid in their bodies, a condition called lactic acidosis. Increased acidity in the blood can lead to vomiting, abdominal pain, extreme tiredness (fatigue), muscle weakness, and difficulty breathing. Less commonly, people with MELAS may experience involuntary muscle spasms (myoclonus), impaired muscle coordination (ataxia), hearing loss, heart and kidney problems, diabetes, and hormonal imbalances.

How common is MELAS?
This disorder is uncommon; its exact incidence is unknown.

How do people inherit MELAS?
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.

What other names do people use for MELAS?
MELAS Syndrome
Mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes
Mitochondrial Myopathy, Lactic Acidosis, Stroke-Like Episode
Myopathy, Mitochondrial-Encephalopathy-Lactic Acidosis-Stroke

Where can I find additional information about MELAS?
The National Information Centre for Metabolic Diseases/
Children Living with Inherited Metabolic Diseases
Climb Building
176 Nantwish Road
Crewe, CW2 6BG
https://www.climb.org.uk/

Muscular Dystrophy Association
National Headquarters
3300 E. Sunrise Drive
Tucson, AZ 85718
1-800-572-1717
https://www.mda.org/

United Mitochondrial Disease Foundation (UMDF)
8085 Saltsburg Road, Suite 201
Pittsburgh, PA 15239
www.umdf.org
1-888-317-UMDF (8633)

This information was developed by the Genetics Home Reference, part of the National Library of Medicine.

Genetics Home Reference, National Library of Medicine. Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (also known as MELAS) . Available at: https://ghr.nlm.nih.gov/condition=mitochondrialencephalomyopathylacticacidosisandstrokelikeepisodes. December 5, 2013.

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