Understanding Mitochondrial Disease

Mitochondrial disease is a group of rare, genetic disorders that affect the mitochondria—the tiny energy-producing structures inside nearly every cell in the human body. Mitochondria are often described as the “powerhouses” of the cell because they convert the food we eat and the oxygen we breathe into usable energy in the form of ATP. That energy fuels everything the body does, from thinking and moving to digesting food and maintaining vital organ function.

When mitochondria do not function properly, the body’s energy supply becomes unstable or insufficient. Because every organ system depends on energy, mitochondrial disease can affect multiple parts of the body at once. This is what makes it so complex and often so difficult to diagnose and treat.

There is no single “mitochondrial disease.” Instead, it is an umbrella term that includes hundreds of different genetic conditions. Some people may be affected primarily in one system, such as the muscles or eyes, while others experience multi-system disease involving the brain, heart, liver, kidneys, digestive tract, or nervous system.

Symptoms can vary widely but often include muscle weakness, fatigue, developmental delays, seizures, stroke-like episodes, gastrointestinal problems, vision or hearing loss, and difficulties with growth or motor function. One of the most challenging aspects of mitochondrial disease is its unpredictability—two people with the same genetic diagnosis may have very different symptoms, severity, and disease progression.

Mitochondrial disease is also progressive in many cases, meaning symptoms can worsen over time as cells become less able to produce the energy needed for normal function. While treatments exist to help manage symptoms and support quality of life, there is currently no cure for most forms of the disease.

What is POLG Disease?

One of the most well-known and serious causes of mitochondrial disease involves a gene called POLG.

The POLG gene provides instructions for making an enzyme called DNA polymerase gamma. This enzyme is essential for replicating and repairing mitochondrial DNA. Unlike most of our DNA, which is housed in the cell nucleus, mitochondria have their own small but critical set of genetic material. This mitochondrial DNA must be constantly maintained so that mitochondria can continue producing energy efficiently.

When there is a disease-causing change in the POLG gene—often referred to as a pathogenic variant or “mutation”—this maintenance system breaks down. As a result, mitochondrial DNA accumulates damage or is depleted over time. Without intact mitochondrial DNA, cells cannot produce energy effectively, and organs that require high amounts of energy begin to fail.

POLG-related disease is considered one of the most common inherited mitochondrial disorders, but also one of the most clinically complex and severe. It can present at any age, from infancy through adulthood, and its progression can vary dramatically depending on the specific genetic variants involved.

The range of symptoms can be broad and often multi-systemic. Neurological involvement is common and may include seizures, developmental regression, migraines, stroke-like episodes, or progressive loss of motor skills. Many individuals also experience muscle weakness, liver dysfunction or liver failure, gastrointestinal dysmotility, vision impairment, and peripheral neuropathy. Because POLG affects the body at such a fundamental level—cellular energy production—it can have widespread and life-altering impacts.

The Human Side of a Genetic Diagnosis

While the science explains what happens at the cellular level, it does not fully capture what families experience when living with mitochondrial disease. Diagnosis is often long and complicated, sometimes taking years. Because symptoms are so varied and can mimic other conditions, families frequently move through multiple specialists and misdiagnoses before arriving at an answer.

Even after a diagnosis is made, there is often uncertainty. Disease progression can be unpredictable, and care typically involves managing symptoms rather than curing the underlying condition. This creates a life shaped by adaptation—learning to respond to changing needs, celebrating small victories, and navigating both hope and heartbreak at the same time.

For my family, mitochondrial disease is not an abstract medical concept. It is deeply personal. My daughter Samantha lived with a POLG-related mitochondrial disease, and her life—though far too short—was filled with resilience, strength, and moments of profound joy. Her journey, along with my brother Ryan’s experience with mitochondrial disease, shaped not only my understanding of this condition but also my purpose.

Why Advocacy Matters

Out of that experience came a commitment that has never left me: to make sure other families do not feel alone in this journey.

For more than two decades, I have worked in mitochondrial disease advocacy, fundraising, and patient engagement—partnering with clinicians, researchers, nonprofit organizations, and families to advance research and improve care. Together with a dedicated community, I have helped raise more than $5 million to support mitochondrial research, clinical programs, and patient and family resources.

Today, I serve on the Board of Directors for the United Mitochondrial Disease Foundation (UMDF), where I continue to advocate for the patient voice and work to accelerate progress toward better treatments and, ultimately, a cure.

This work is rooted in a simple belief: that every patient’s story matters, and that progress happens faster when those stories are heard.

For me, this is not just advocacy. It is love turned into action.

Watch our video here to learn about this disease and our charge to raise awareness and someday a cure.