When Cellular Structures Become Diseased: Mitochondrial Disorders

Many human cells contain structures called mitochondria. They generate energy for the cell. In mitochondrial disorders, energy metabolism is impaired because of genetic changes, and the resulting symptoms can vary widely.

What are mitochondria?

Mitochondria are cellular organelles with their own genetic material. They are found in almost all cells that contain a nucleus and are especially numerous in tissues with high energy requirements, including:

• Muscle cells
• Sensory cells
• Egg cells
• Nerve cells

Their main task is to produce energy through metabolic processes such as oxidative phosphorylation. Sugars and fats are converted into ATP, the usable energy currency of the cell. Numerous proteins are involved in this process.

When genetic variants disrupt mitochondrial function, tissues with high energy requirements may be particularly affected. This includes the nervous system, muscles, heart, liver and eyes.

How do mitochondrial disorders present?

Symptoms often begin in childhood or adolescence, but mitochondrial disease can become apparent at any age. These disorders are considered rare and are estimated to affect approximately one in several thousand people.

When mitochondrial energy production is impaired, cells may first lose function and may eventually die. Almost any organ can be affected. Possible symptoms include:

• Muscle weakness or cramps
• Visual impairment
• Epileptic seizures
• Gastrointestinal problems
• Heart or liver disease
• Diabetes
• Increased susceptibility to infection
• Short stature
• Stroke-like episodes

Mitochondrial disorders may result from mutations in mitochondrial DNA or in genes located in the cell nucleus. These changes can be inherited or arise spontaneously.

More than 250 genes have already been associated with mitochondrial disease, and additional genes are likely still unknown.

Why mitochondrial research matters

Mitochondria play a central role in human health. Many chronic degenerative diseases are associated with altered mitochondrial function, including Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, amyotrophic lateral sclerosis and cardiovascular disease.

This does not necessarily mean that mitochondrial dysfunction is the sole cause of these conditions. It may be one contributing mechanism among many. Mitochondrial changes are also being investigated in autoimmune disease and cancer.

What can be done when mitochondrial disease is suspected?

When symptoms suggest a mitochondrial disorder, further assessment should take place at a specialized center. Diagnostic evaluation may include blood tests, organ-specific examinations, genetic testing and, in selected cases, a muscle biopsy.

Because hormonal disorders may occur alongside mitochondrial disease, endocrine parameters may also require regular monitoring.

Families affected by a confirmed genetic mitochondrial disorder may benefit from genetic counseling. A detailed family history can help identify other potentially affected relatives and clarify the possible risk for children.

Treatment

There is currently no universal cure for mitochondrial disorders. Treatment is usually directed at symptoms and the prevention of complications. Diabetes, epilepsy, cardiac disease and other manifestations are treated individually.

Physical activity may be beneficial for some patients, particularly carefully supervised endurance exercise. However, intensity must be adapted to the individual condition and energy limits.

Selected nutrients involved in cellular metabolism are sometimes used as supportive measures. Their use should always be discussed with specialists because evidence and requirements vary between different forms of mitochondrial disease.

Conclusion

Mitochondrial disorders are complex genetic diseases that can affect many organs. Early diagnosis, specialist care, symptom-specific treatment and individually adapted exercise may help preserve function and quality of life.