Mitochondrial Encephalomyopathy with Lactic Acidosis and Stroke-like Episodes

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Mitochondrial Encephalomyopathy with Lactic
Acidosis and Stroke-like Episodes

• (MELAS)

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What is MELAS?

• Mitochondrial Mutation in the mitochondria
• Encephalo- Occurs in the head
• Myopathy General term for muscle disease
• Lactic Acidosis The blood gets too acidic
• Stroke-like Episodes Brain-related symptoms of
  bleeding or blockage

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Characteristics

• It is the most common maternally inherited
  mitochondrial disease
• Clinical Features Strokes, myopathy, muscle
  twitching, dementia, and deafness
• To a lesser extent vomiting, migrainelike
  headaches, diabetes, droopy eyelids, muscle
  weakness, and short stature

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More Characteristics

• MELAS affects no specific race or gender more so
  than others
• Presentation of the disease occurs with the first
  stroke-like episode (usually 14-15 yrs of age)
• This is a progressive disorder with a high
  mortality rate

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How does MELAS work?

• Abnormal mitochondria do not metabolize pyruvate
• Excess pyruvate is reduced to lactic acid which
  accumulates in blood and other fluids
• Large clumps of abnormal mitochondria form in the
  walls of small arteries and capillaries in the
  brain and muscles

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What causes MELAS?

• There are at least 6 different point mutations
  associated with MELAS
• 80 of cases have a A to G point mutation in the
  tRNA (Leu) gene at bp 3243
• 7.5 of cases have a T to C point mutation in the
  tRNA (Leu) gene at bp 3271

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(No Transcript)
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Causes (contd.)

• All of these mutations are heteroplasmic
• Heteroplasmic within a single cell, there is a
  mixture of mitochondria, some containing mutant
  DNA and some containing normal DNA
• This feature of mitochondrial diseases might
  offer a solution to the varied rates of
  progression and onset of the disease

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References

• Scaglia, Fernando, MD. MELAS Syndrome.
  http//www.emedicine.com/ped/topic1406.htm.
  October 26, 2004
• http//herkules.oulu.fi/isbn9514255674/html/graphi
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