What is MELAS syndrome?
MELAS syndrome is a rare genetic condition that affects the way the body’s cells make energy.
Every cell in the body needs energy to work normally, and when this process doesn’t run smoothly, it can affect organs that rely on energy the most — especially the brain and muscles.
The name “MELAS” describes the main features of the condition:
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M – Mitochondrial
Mitochondria are the tiny “power stations” inside our cells that make energy. In MELAS syndrome, these power stations don’t work as well as they should. -
E – Encephalopathy
This means the brain is affected, leading to changes in thinking, behaviour or awareness. -
L – Lactic
Lactic acid can build up when the body’s cells struggle to make energy efficiently. -
A – Acidosis
This build-up of lactic acid can make the body’s chemical balance more acidic, which can cause nausea, tiredness and rapid breathing. -
S – Stroke-like episodes
People may experience sudden symptoms that look like a stroke, such as weakness, vision changes or confusion — but these are caused by problems with energy in the brain, not blocked blood flow.
Symptoms often begin in childhood or early adulthood, but the condition can look different from person to person.
Although MELAS syndrome is a lifelong condition, understanding what’s happening in the body, and getting the right support early, can make a real difference to daily life and long-term health.
What causes MELAS syndrome?
The causes of MELAS syndrome are linked to changes in the genes inside the mitochondria — the parts of our cells responsible for making energy. These changes affect how well the mitochondria work, meaning the body can’t produce energy as efficiently as it needs to.
MELAS is usually passed down through families in a pattern called mitochondrial inheritance. However, not everyone in the family will develop symptoms, and these can vary widely even between close relatives.
In some cases, MELAS can happen without a family history, caused by a new genetic change that wasn’t present in either parent. Doctors can confirm this through genetic testing.
What are the symptoms of MELAS syndrome?
The symptoms of MELAS syndrome are caused by the body not producing enough energy, especially in the brain and muscles – which rely on energy the most.
Symptoms can vary widely from person to person, and may appear at different ages. Common symptoms include:
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Stroke-like episodes – sudden changes such as weakness, vision problems, confusion or difficulty speaking. These can look like a stroke but are caused by low energy in the brain, not a blocked blood vessel.
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Muscle weakness and tiredness – many people feel unusually fatigued or find their muscles tire more quickly than expected.
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Headaches – often severe, and sometimes linked to stroke-like episodes or changes in energy levels.
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Hearing loss – gradual changes in hearing can occur over time.
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Seizures – some people experience epileptic seizures as part of the condition.
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Movement or coordination difficulties – problems with balance, walking or fine motor skills.
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Digestive issues – such as vomiting, poor appetite or difficulty maintaining weight.
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Lactic acidosis – a build-up of lactic acid in the body, which can cause nausea and changes in breathing patterns.
There is currently no cure for MELAS, but treatments are available to help manage symptoms. Early diagnosis and support can make a big difference in managing day-to-day life and planning the right care.
