Mitochondrial diseases are generally difficult to diagnose.1 Patients frequently share that they saw multiple physicians over a number of years before being diagnosed definitively.2 The difficulty lies in the fact that symptoms tend to affect multiple parts of the body and resemble those of more common diseases. Genetic testing is the most accurate way to confirm mitochondrial disease. Other methods for diagnosis may involve analyzing blood or muscle tissue samples for the presence of abnormal mitochondria.1
Key Symptoms of Mitochondrial Disease2, 3
While the diagnosis process can be challenging and symptoms vary from person to person and across the different types of mitochondrial disease, there are key symptoms that may implicate mitochondrial disease. These symptoms can help signal when it may be time to seek medical attention and ask about mitochondrial disease. Resources from The Mitochondrial Medicine Society (MMS) include a study in which researchers categorized these symptoms as “red-flag findings” to watch for mitochondrial disease.
Muscle Weakness, Chronic Fatigue and Exercise Intolerance:
Mitochondrial disease often weakens skeletal muscles. This muscle weakness impairs the ability to move around easily and can cause difficulty with balance and coordination in day-to-day activities.
In addition to weakness, some people with mitochondrial disease may experience crippling fatigue or exercise intolerance, with painful muscle cramps and extreme exhaustion following even the most minor physical activity. Some may find even climbing a flight of stairs or walking to the mailbox exhausting.
Seizures and Neurological Complications:
Mitochondrial diseases can cause a range of symptoms in the brain with varying degrees of severity, including seizures, stroke, dementia and recurrent migraine headaches.
People with mitochondrial disease may also experience problems with their memory, other impaired cognitive function or developmental delays.
Vision Loss and Vision Issues:
The muscle weakness associated with many forms of mitochondrial disease can affect muscles controlling the eyes and eyelids. These weakened muscles can cause slowed eye movements, droopy eyelids and an inability to move the eyebrows.
In some cases, mitochondrial dysfunction may lead to the death of nerves that are critical to vision. Symptoms may start with blurred vision in one or both eyes and can eventually progress to vision loss.
Problems Swallowing and Digesting Food:
In some forms of mitochondrial disease, the muscles controlling the digestive tract may weaken, which can cause problems with swallowing and digesting food, as well as abdominal pain or blockage. People with mitochondrial disease may also experience vomiting, diarrhea and nausea caused by these weakened muscles.
Enlarged Heart and Cardiovascular Dysfunction:
Some forms of mitochondrial disease may result in an irregular heartbeat or an enlarged, weakened heart. Over time, the disease may prevent the heart from pumping blood normally.
Additional Symptoms of Mitochondrial Disease2, 3
While those symptoms are considered “red flags,” the study also found other common symptoms in people with mitochondrial disease.
Here are a few examples.
Neck Muscle Weakness:
Weakened muscles in the face and neck can cause slurred speech, contribute to difficulty swallowing or lead to an inability to hold the neck upright.
Hearing loss, or deafness, is a feature of some mitochondrial diseases.
Some mitochondrial diseases may weaken the muscles that support the lungs, causing difficulty breathing or shortness of breath. Damaged mitochondria in certain areas of the brain can also cause difficulty breathing.
Disclaimer: The above list of symptoms is not meant to be exhaustive, and information in this article is not intended to serve as medical advice. If you have questions about symptoms and whether you might be affected by mitochondrial disease, speak with a healthcare professional.
Ref 2. Pfeffer G and Chinnery PF. Diagnosis and treatment of mitochondrial myopathies. Ann Med. 2013 Feb;45(1):4-16.
Ref 3. Grier, Hirano, Karaa, et. al. Diagnostic odyssey of patients with mitochondrial disease. Neurol Genet. 2018 April; 4(2): e230.