MELAS Syndrome

  • Medical Author:
    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

  • Medical Editor: Frederick Hecht, MD, FAAP, FACMG
    Frederick Hecht, MD, FAAP, FACMG

    Frederick Hecht, MD, FAAP, FACMG

    Frederick Hecht, MD, lives in Scottsdale, Arizona. Dr. Hecht is a Pediatrician and Medical Geneticist and is certified by both the American Boards of Pediatrics and Medical Genetics. Dr. Hecht was born and raised in Baltimore and attended Dartmouth College in Hanover, N.H. and the Sorbonne at the University of Paris receiving his BA degree cum laude with distinction from Dartmouth.

Stroke visual guide

What Is Mitochondrial Encephalopathy, MELAS?

MELAS is the acronym for Mitochondrial Encephalopathy, Lactic Acidosis, and Stroke-like episodes.

MELAS is a form of dementia. It is caused by mutations in the genetic material (DNA) in the mitochondria. While most of our DNA is in the chromosomes in the cell nucleus, another important cell structure that carries DNA is the mitochondrion. Much of the DNA within the mitochondrion is used to manufacture proteins that help in the mitochondrion's energy-producing function.

As a result of the disturbed function of their cells' mitochondria, patients with MELAS develop brain dysfunction (encephalopathy) with seizures and headaches, as well as muscle disease with a buildup of lactic acid in the blood (lactic acidosis), temporary local paralysis (strokelike episodes), and abnormal thinking (dementia).

What is MELAS?

MELAS is a rare genetic disorder which results in stroke and dementia. MELAS is an abbreviation that stands for Mitochondrial Encephalopathy, Lactic acidosis, and Stroke-like episodes.

What causes MELAS?

MELAS syndrome is caused by mutations in the genetic material (DNA) in the mitochondria. While most of our DNA is in the chromosomes in the cell nucleus, some of our DNA is in another important structure called the mitochondrion (plural: mitochondria).

The mitochondria are located outside the nucleus in the cell's cytoplasm. Each mitochondrion has a chromosome made of DNA that is quite different from the better known chromosomes in the nucleus. The mitochondrial chromosome is much smaller; it is round (whereas the chromosomes in the nucleus are normally shaped like rods); there are many copies of the mitochondrial chromosome in every cell; and no matter whether we are male or female, we inherit all of our mitochondrial chromosome from our mother.

Much of the DNA in our mitochondria is used to manufacture proteins involved in the key function of mitochondria -- to produce energy and power the cells in our body.

What are the symptoms of MELAS?

As a result of the disturbed function of their cells' mitochondria, patients with MELAS develop

  • brain dysfunction (encephalopathy) with seizures and headaches,
  • as well as muscle disease with a build-up of lactic acid in the blood (a condition called lactic acidosis),
  • temporary local paralysis (stroke-like episodes), and
  • abnormal thinking (dementia).

How is MELAS diagnosed?

The diagnosis of MELAS is usually suspected on clinical grounds. However, confirmation of the diagnosis usually requires a muscle or brain biopsy. The muscle biopsy shows characteristic ragged red fibers; a brain biopsy shows stroke-like changes.

When do people with MELAS develop symptoms?

MELAS can affect people at very different times in life, ranging from age 4 to age 40 or more. However, most patients with MELAS syndrome show symptoms before they are 20 years old.

Medically Reviewed by a Doctor on 8/23/2016

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