Mitochondrial disease affects people in different ways. The most common problems are mild weakness of the arms and legs, droopy eyelids (ptosis) and difficulty in moving the eyes (ophthalmoplegia). Others may have exercise intolerance, which means weakness of the arms and legs gets worse after physical exertion. This may also include nausea, headache, light-headedness and heart palpitations.
In severe cases, muscle weakness may be obvious, especially in small babies who may be very ‘floppy’ (hypotonia) and have difficulty breathing and feeding. Some forms of mitochondrial disease affect the brain. This can lead to developmental delay and/or loss of skills (regression) in children (such as in Leigh disease), epilepsy, stroke-like episodes and progressive loss of memory. Not all mitochondrial myopathies with brain involvement get worse, but some will. The light-sensitive membrane at the back of the eye (the retina) may also be affected and hearing difficulties are common.
Heart problems are common, so doctors recommend regular check-ups. Some patients may develop a very slow heart rate and this may require a pacemaker – an electrical device that helps the heart to beat properly. Certain forms of mitochondrial disease put individuals at risk of developing diabetes, kidney problems, liver dysfunction or other organ problems. Therefore, ongoing management and follow-up need to be tailored to individual patients.
It is important to have a regular intake of calories during the day. If this becomes difficult – in the case of young children, or if you’re fasting voluntarily or because of illness – there will be increased demand on mitochondria. Certain drugs may also affect mitochondrial function and specialists generally recommend limiting alcohol. If you’re in any doubt, consult your doctor.