What are mitochondria and what do they do?
Mitochondria are tiny structures inside our cells. Their main job is to turn the food we eat and the oxygen we breathe into a usable form of energy called ATP. They do this through a chain of five protein complexes, known as the respiratory chain.
Cells with the highest energy needs have the most mitochondria. That’s why the brain, muscles, heart, liver, eyes and ears are often affected first.
What causes mitochondrial disease?
Mitochondrial disease is caused by changes (variants) in genes that mitochondria need to work. These genes sit in two places:
- Mitochondrial DNA (mtDNA): a small set of 37 genes inside the mitochondria themselves.
- Nuclear DNA: a large number of genes in the cell nucleus that make proteins mitochondria rely on.
Head over to our Research Zone to find out more about the difference between mitochondrial and nuclear DNA.
When a variant stops the respiratory chain working well, cells make less energy than they need. Cells that are short of energy may stop working properly and, in severe cases, die. This is why mitochondrial disease can be serious when vital organs are affected.
Passing on a genetic variant is never anyone’s fault.
How is mitochondrial disease inherited?
Mitochondrial disease can be inherited in several different ways, which is one reason it can be so confusing to patients and families. The pattern of inheritance depends on where the genetic change occurs, and understanding these differences is the first step towards making sense of how the condition is passed on and why it can look so different from one person to another.
Head over to our Research Zone to discover more about understanding inheritance patterns in mitochondrial disease.
This is why the same variant can cause very different symptoms, even within one family. Families can speak to a clinical geneticist about their own risks, and we explain reproductive options and mitochondrial donation separately.
Who can get mitochondrial disease, and how common is it?
Mitochondrial disease is rare, but it can affect anyone, in any family and at any age. About 1 in 4,300 people are estimated to be affected by a mitochondrial disease in adulthood.
Some people live with mild problems for years before a diagnosis. Others have complex needs from early in life.
What are the symptoms?
Symptoms depend on which organs are affected. These are examples, not a checklist, and many have other causes.
- Brain and nerves: Seizures, developmental delay, stroke-like episodes, migraines, movement problems
- Muscles: Weakness, pain, fatigue, tiredness after little effort
- Heart: Weakened heart muscle, irregular heart rhythm
- Eyes: Drooping eyelids, limited eye movement, vision loss
- Ears: Hearing loss
- Gut and liver: Reflux, constipation, feeding difficulties, liver problems
- Hormones and kidneys: Diabetes, poor growth, kidney problems
Learn about causes, common signs and symptoms with our guide to mitochondrial disease symptoms. And if you’re worried about symptoms in yourself or your child, please speak to your GP.
Are there different types of mitochondrial disease?
Yes. Some are named as syndromes, based on a recognisable pattern of symptoms, such as Leigh syndrome, MELAS, MERRF, Alpers’ and LHON. Others are grouped by which respiratory chain complex is affected (for example Complex I) or by the gene involved. Read more on our mitochondrial syndromes page, and head over to our mitochondrial disease glossary for unfamiliar terms.
How is mitochondrial disease diagnosed?
Diagnosis can take time, because the symptoms are wide-ranging and overlap with other conditions. Doctors may use:
- A clinical assessment and family history
- Blood and urine tests, including lactate
- Brain scans and heart or eye tests
- Genetic testing, which now identifies the cause in many people
- Sometimes a muscle biopsy to look at how mitochondria are working
Read all about these tests, and how specialists reach a diagnosis, over on our mitochondrial disease diagnosis page.
How is mitochondrial disease treated?
There is currently no cure, and very few treatments for specific types of mitochondrial disease. Care focuses on managing symptoms and protecting health, usually by a team of specialists, which may include:
- Neurology, cardiology, ophthalmology and hearing specialists
- Dietitians and speech and language therapists
- Physiotherapy and occupational therapy
- Emergency care plans for periods of illness or fasting, which can put extra strain on energy supply
Some medicines can be harmful for people with mitochondrial disease, so always check before taking new ones. You can find up-to-date information on this over on our drug information page. Evidence for vitamins and supplements is limited, so be sure to talk to your specialist first.
The Lily Foundation has funded over 20 research projects looking for treatments and improved ways to diagnose and care for patients.
What is the outlook?
It varies enormously. Some people have mild symptoms for most of their lives. Others are seriously affected in infancy or childhood, and mitochondrial disease can shorten life. No two cases of mitochondrial disease are the same, therefore your specialist team is the best source of information about your own situation.
Living with mitochondrial disease
“The Lily Foundation is a charity very close to our family’s hearts, a charity we are so very passionate about. They’ve helped us in many ways, from funding equipment to holiday breaks, support and someone to talk to.” – Emma (Teddie’s mum)
The support The Lily Foundation offers to patients and families across the UK takes many forms, from counselling and support weekends to practical advice and emotional support. You can also read our Guide to Mitochondrial Disease or ask us a question.
How The Lily Foundation can support you
The Lily Foundation was founded in 2007 by Liz Curtis in memory of her daughter Lily, who died from mitochondrial disease at eight months old. Before the charity existed, there was no dedicated support service for mitochondrial disease patients in the UK. Very little was known about the condition and there was hardly any accessible information available for Liz and her family to refer to. Today we support more than 1,500 patients and families, and several of our team have personal experience of mito themselves, so we’re uniquely placed to offer support and advice.
What you need changes over time. This is how we can help at each stage.
If you’re newly diagnosed
Start with our Guide to Mitochondrial Disease and questions and answers, or call us on 0300 400 1234. Private Facebook groups connect adults and families with others who understand.
Living with it day to day
Join our virtual coffee mornings (weekly, with monthly evening sessions) or our Zoom Room webinars, where specialists cover topics such as coping with mitochondrial disease and physiotherapy.
A parent or carer
Our annual Family Support Weekend gives parents time to meet others, hear from mitochondrial disease experts and relax, while children enjoy their own activities. Parents, adult patients and carers can also apply to our Wish Fund.
A young person or adult with mito
The Young Adult Support Weekend in the Lake District and our Adult Support Weekend bring people together in accessible, relaxed settings.
Needing financial help
The Wish Fund offers grants towards things such as specialist equipment, a home or garden adaptation or a short break.
Wanting to talk to someone
We offer free, confidential online counselling for people aged 18 and over, delivered with specialist rare disease counsellors Rareminds. See emotional support, including bereavement support.
Wanting to meet your specialists
Regular Patient Information Days are co-hosted with the specialist NHS mitochondrial clinics in Newcastle, Oxford and London.
How we fund research into treatments
The Lily Foundation is the largest charitable funder of mitochondrial disease research in Europe. Since 2016 we’ve funded over £3 million into more than 20 projects, with two aims: finding better ways to diagnose mitochondrial disease, and finding treatments.
The patient voice shapes the work too: through our IMPACT panel, patients and carers help set priorities, shape trials and explain results. If you have lived experience of mitochondrial disease, either as a patient, parent or carer, you can find out how to be part of mito research.
What our research has already changed
- Faster, less invasive diagnosis. We launched the Lily Exome Sequencing project in 2012, which let scientists test hundreds of genes at the same time, and has since been adopted by the NHS. We continue to fund diagnostics today through our nationwide Precision Diagnostics project.
- A change in UK law. In 2015 we successfully lobbied for the law to allow mitochondrial donation, an IVF technique that helps some women with mitochondrial disease have children without passing on the condition. Research published in July 2025 confirmed early success with eight healthy babies born as a result of the technique. Read more about mitochondrial donation.
See every project on our Lily-funded research page, and current UK trials and studies.
Building a national effort
- The LifeArc Centre for Rare Mitochondrial Diseases. A £7.5 million virtual centre, funded by LifeArc and Muscular Dystrophy UK and led by the University of Cambridge, working on a 5-year project to turn laboratory discoveries into treatments. Officially launched at the House of Lords in May 2025. The Lily Foundation leads its patient and public involvement and sits on its management group, so lived experience guides its priorities. Read more.
- The UK Mitochondrial Disease Research Institute. Our 10-year vision for a virtual institute, directed by Professor Mike Hanna, to shorten the road from diagnosis to discovery and from discovery to treatments and an eventual cure. Read more.
- International work. We are a board member of International Mito Patients, a global group supporting everyone affected by mitochondrial disease.
Where research is heading
No treatment can yet cure mitochondrial disease, and most research is still at an early stage. Current work includes better diagnosis, treatments for particular mito syndromes, managing symptoms such as seizures, gut problems, balance issues and hearing loss, and gene therapy techniques. Our Research Zone explains new studies in plain English as they are published.