Mitochondrial diseases

Mitochondria are structures found inside almost every cell in the body. They act as the cell’s ‘power stations’, producing the energy needed for organs and tissues to function normally.

In mitochondrial disease, the mitochondria do not work properly, so cells cannot generate enough energy.

Because energy is needed throughout the body, mitochondrial disease can affect many different organs and systems. The symptoms experienced by patients and the severity of disease vary greatly between individuals.

Mitochondrial disease is caused by genetic changes in any of more than 400 genes that code for the proteins needed for mitochondria to function properly.

These genetic changes may be inherited from one or both parents, or they may occur for the first time in the affected child or adult.

Mitochondrial disease can affect people at any age, although many forms present during infancy or childhood.

Symptoms vary depending on which organs are most affected and how severe the energy deficiency is.

Common symptoms include:

• Poor growth
• Developmental delay
• Muscle weakness
• Poor exercise tolerance or fatigue
• Seizures
• Problems with balance or coordination
• Vision or hearing problems
• Feeding difficulties
• Gastrointestinal symptoms such as vomiting or constipation
• Heart, liver or kidney problems

Some people may have mild symptoms affecting only one part of the body. Others may have more severe disease affecting more than one organ of the body – this is known as multi-system disease.

Diagnosing mitochondrial disease can be complex because symptoms overlap with many other conditions.

Doctors will usually begin with a detailed medical history and physical examination. Investigations may include:

• Blood and urine tests
• Genetic testing
• Brain imaging such as MRI
• Heart tests including ECG and echocardiogram
• Muscle biopsy in selected cases
• Other specialist metabolic investigations

A diagnosis is often made by combining clinical findings (the symptoms and the physical examination), laboratory results and genetic testing.

There is currently no curative treatment for most mitochondrial diseases. Instead, treatment focuses on managing symptoms and supporting affected organs.

Treatment may include:

• Vitamins or supplements
• Medicines to control seizures or other symptoms
• Cardiac, respiratory or endocrine support
• Physiotherapy and occupational therapy
• Specialist nutritional support
• Avoidance of prolonged fasting during illness in some mitochondrial disorders

Children with mitochondrial disease are usually managed by a multidisciplinary team including metabolic specialists, neurologists, dietitians, therapists and specialist nurses.

The outlook varies widely depending on the specific type of mitochondrial disease and which organs are affected.

Some children have relatively mild symptoms and stable disease over many years. Others may have progressive disease requiring intensive medical support.

Early diagnosis and specialist management can help improve quality of life, manage complications and support development.

The Lily Foundation

The UK's leading charity dedicated to fighting mitochondrial disease, The Lily Foundation raises awareness and funds research and support.

The Freya Foundation

The Freya Foundation aims to raise awareness for the condition called PDH, or pyruvate dehydrogenase deficiency complex.