Chronic progressive external ophthalmoplegia

The signs and symptoms of chronic progressive external ophthalmoplegia (CPEO) typically begin in young adults between the ages of 18 and 40.^[1][2] The most common symptoms in affected individuals include drooping eyelids (ptosis) and weakness or paralysis of the eye muscles (ophthalmoplegia). The condition may be unilateral (affecting one eye) or bilateral (affecting both eyes).^[3] Some affected individuals also have weakness of the skeletal muscles (myopathy), specifically of the arms, legs, and/or neck. This may be especially noticeable during exercise.^[1][2] Muscle weakness may also cause difficulty swallowing (dysphagia).^[2]

Sometimes, CPEO may be associated with other signs and symptoms. In these cases, the condition is referred to as "progressive external ophthalmoplegia plus" (PEO+). Additional signs and symptoms can include hearing loss caused by nerve damage in the inner ear (sensorineural hearing loss), weakness and loss of sensation in the limbs due to nerve damage (neuropathy), impaired muscle coordination (ataxia), a pattern of movement abnormalities known as parkinsonism, or depression.^[2]

CPEO can also occur as part of other underlying conditions such as Kearns-Sayre syndrome. These conditions may not only involve CPEO, but various additional features that are not shared by most individuals with CPEO.^[2]

Chronic progressive external ophthalmoplegia (CPEO) can be inherited, or it can occur sporadically (due to a new mutation in an individual with no history of the condition in the family).

CPEO is considered a "mitochondrial disorder." This is because all the genetic mutations that can cause CPEO ultimately result in dysfunction of the mitochondria, which are structures in our cells that produce energy required for normal cell function. While most of our DNA is located in the cell's center (nuclear DNA), some of our DNA is located within the mitochondria (mitochondrial DNA).^[1] CPEO can be caused by mutations in any of several genes, which may be located in mitochondrial DNA or nuclear DNA. It has different inheritance patterns depending on the gene involved in the affected individual.^[2]

Unlike nuclear DNA which is inherited from both the mother and the father, mitochondrial DNA is inherited from only the mother. In CPEO, the affected mitochondria (i.e., the ones carrying the mutations) are found only in the skeletal muscle cells. These mitochondrial DNA mutations are almost always sporadic (occurring by chance for the first time in the affected individual). Nuclear gene mutations that cause CPEO may be inherited in an autosomal recessive or autosomal dominant manner, depending on the gene involved.^[1] The risk for other family members to be affected depends on the genetic cause and the inheritance pattern in the family.

Ptosis caused by chronic progressive external ophthalmoplegia (CPEO) can be corrected by surgery, or by using glasses that have a “ptosis crutch” to lift the upper eyelids.^[4] Strabismus surgery can be helpful in carefully selected patients if diplopia (double vision) occurs.^[5]

Some individuals with a deficiency of coenzyme Q10 have CPEO as an associated abnormality. Coenzyme Q10 is important for normal mitochondrial function. In individuals with this deficiency, supplemental coenzyme Q10 has been found to improve general neurologic function and exercise tolerance. However, coenzyme Q10 has not been shown to improve the ophthalmoplegia or ptosis in people who have isolated CPEO.^[1]

Chronic progressive external ophthalmoplegia (CPEO) can be an isolated condition, or it can occur as part of other underlying conditions, such as ataxia neuropathy spectrum and Kearns-Sayre syndrome. These conditions may involve not only CPEO, but various additional features that are not shared by most individuals with CPEO.^[2] Individuals with isolated CPEO generally have a normal life expectancy. While symptoms tend to worsen over time, the specific symptoms and their severity can vary greatly from person to person. Therefore, when symptoms first appear, the course of the condition is very difficult to predict.^[1][6]

For individuals with additional symptoms or another underlying condition associated with CPEO, the prognosis depends on the specific signs and symptoms present and/or the outlook associated with the underlying condition in the affected individual. For this reason, obtaining an accurate diagnosis is very important.