Technically speaking, chronic progressive external ophthalmoplegia is a disorder where the patient has slowly progressive, bilateral, and usually symmetric ocular motility deficit due to paralysis of the extraocular muscles followed by eyelid ptosis (1). This is a rather complicated way to say that your eye lids droop (ptosis) and the muscles that move your eyeball become weakened or paralyzed (external opthalmoplegia). Chronic means a persistent disease that occurs slowly over the lifetime of the patient and progressive implies that the symptoms increase or become worse over time. This condition is actually part of a class of neuromusclar diseases called mitochondrial myopathy and can be found in combination with other mitochondrial myopahties, especially with Kearns-Sayre syndrome. CPEO is the most common form of mitochondrial myopathy.
Chronic progressive external ophthalmoplegia is caused by damage to mitochondria, which are the energy source of cells and, when damaged, can cause problems in cells that require a lot of energy to work (like muscle cells). In mitocondrial myopathies, the DNA inside the mitochondria is damaged and causes the problems associated with the disease. Since CPEO is a genetic disease, it can be inherited but mitochondrial DNA is a little different than the other DNA found in your cells. Mitochondria are only inherited from your mother and its "mitochondrial DNA" mutates, or changes, more quickly than "genomic DNA," or the DNA responsible for the information needed to construct every living organism. Because of the quick rate of mutations in mitochondrial DNA, CPEO can be inherited or can also be a newly acquired, or spontaneous, defect in the affected individual.
Signs and Symptoms
Most often, chronic progressive external ophthalmoplegia occurs in young adults and is often noticed by an increased drooping of the patient’s eyelids. Weakness of the eye or difficulty moving the eyeball can also accompany the weakness and drooping of the eyelids. Sometimes, weakness of the arms and legs can also occur and results, most noticeably, in intolerance for exercise or quickly tiring after activity. Other less common symptoms include cardiomyopathy, or heart disease, cataracts, depression, and peripheral neuropathy, or damage to the nerves in the body.
Unfortunately, there are no know treatments to cure or lessen the severity of chronic progressive external ophthalmoplegia. However, some of the symptoms can be managed. Ptosis, or drooping of the eylids, can sometimes be corrected through surgery and other surgeries can also help if vision is impaired. In other mitochondrial myopathies, supplements containing coenzyme Q10 can help with neurologic function. Although some people with CPEO may have a coenzyme Q10 deficiency, the supplement has not been found to help with ptosis or ophthalmoplegia, but may help with exercise intolerance or other symptoms.
Luckily, people with CPEO have a good prognosis and the disease should not effect other aspects of health. While the disease is progressive and symptoms tend to get worse over time, the severity of the disease differs with each patient. Occasionally, people with chronic progressive external ophthalmoplegia may develop more severe disease involving not only the eyes but other muscles and organs as well (2). Because of the differing levels of disease, it is important for those with CPEO to regularly visit their doctor to monitor their disease progression.
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