Mitochondrial disease is a group of genetic conditions that affect how mitochondria produce energy inside the body’s cells. Often described as the “powerhouses of the cell,” mitochondria convert nutrients and oxygen into energy needed for organs and tissues to function properly.

Because mitochondria are found in almost every cell, mitochondrial disease can affect several parts of the body. The brain, muscles, heart, kidneys, liver, eyes, ears and digestive system can all be affected. The symptoms and their severity can vary significantly from one person to another, even within the same family.

Common symptoms of mitochondrial disease may include muscle weakness or pain, poor growth, hearing or vision problems, developmental difficulties, digestive problems, seizures, migraines, breathing difficulties and episodes of fainting. Some symptoms may be present from birth, while others can appear later in life.

Mitochondrial disease is usually caused by changes in genes that interfere with the mitochondria’s ability to produce energy. These genetic changes may be inherited from one or both biological parents, while some cases develop through new genetic changes without a known family history. Mitochondrial DNA has a unique inheritance pattern because it is generally passed from mother to child.

Not every problem involving mitochondria is a genetic mitochondrial disease. Other conditions can cause secondary mitochondrial dysfunction, meaning the mitochondria become less effective because of another disease.

The effects of mitochondrial disease can be significant because reduced energy production can interfere with the normal function of multiple organs. Complications may include diabetes, kidney or liver problems, heart disease, neurological difficulties and gastrointestinal conditions.

Understanding mitochondrial disease is important because its wide range of symptoms can make the condition difficult to recognise. Greater awareness can help explain why symptoms may affect several body systems at once.