Chronic progressive external ophthalmoplegia

A mitochondrial disorder affecting eye muscles

Chronic progressive external ophthalmoplegia
Synonyms	Progressive external ophthalmoplegia, CPEO
Pronounce	/ˈɒfθəlmoʊˌpliːdʒə/
Specialty	N/A
Symptoms	Gradual paralysis of the extraocular muscles, ptosis, limited eye movement, muscle weakness, exercise intolerance
Complications	Dysphagia, cardiomyopathy, sensorineural hearing loss, diabetes mellitus
Onset	Typically in young adulthood or middle age
Duration	Chronic and progressive
Types	CPEO, CPEO plus (includes systemic symptoms)
Causes	Mutations in mitochondrial DNA (mtDNA) or nuclear DNA, such as POLG, TWNK, RRM2B
Risks	Family history of mitochondrial disease, genetic mutations
Diagnosis	Muscle biopsy, genetic testing, EMG, MRI, ophthalmological exam
Differential diagnosis	Myasthenia gravis, Graves' ophthalmopathy, Kearns–Sayre syndrome, oculopharyngeal muscular dystrophy
Prevention	None known; genetic counseling may be helpful
Treatment	Supportive care, eyelid surgery, eye protection, physical therapy, aids for ptosis
Medication	No disease-specific drugs; coenzyme Q10 and vitamins may be used supportively
Prognosis	Slowly progressive; often compatible with normal life expectancy
Frequency	Rare; exact incidence unknown
Deaths	Not typically fatal; related systemic complications may affect prognosis

Chronic progressive external ophthalmoplegia (CPEO) is a rare neuromuscular disorder characterized by slowly progressive paralysis of the extraocular muscles, which are responsible for controlling eye movements. This condition leads to ptosis (drooping of the eyelids) and limited eye movement, often resulting in diplopia (double vision). CPEO is primarily associated with mitochondrial myopathy, a type of mitochondrial disease.

Pathophysiology

CPEO is caused by defects in the mitochondria, the energy-producing structures within cells. These defects can result from mutations in nuclear DNA or mitochondrial DNA (mtDNA). The mutations lead to impaired energy production, particularly affecting tissues with high energy demands, such as the muscles controlling eye movement. The accumulation of dysfunctional mitochondria in these muscles results in their progressive weakness and paralysis.

Clinical Features

The hallmark of CPEO is the gradual onset of ophthalmoplegia, which typically begins in adulthood. Patients often present with:

• Ptosis: Drooping of one or both eyelids, which may be the initial symptom.
• Ophthalmoplegia: Limited movement of the eyes in all directions, leading to difficulty in tracking objects and diplopia.
• Facial Weakness: Some patients may experience mild weakness of the facial muscles.
• Muscle Weakness: In some cases, CPEO may be associated with generalized muscle weakness, particularly in the limbs.

Diagnosis

The diagnosis of CPEO is based on clinical examination, family history, and specialized tests. Key diagnostic tools include:

• Ophthalmologic Examination: To assess the extent of eye movement limitation and ptosis.
• Muscle Biopsy: May reveal characteristic "ragged-red fibers," indicative of mitochondrial myopathy.
• Genetic Testing: To identify mutations in mtDNA or nuclear DNA associated with CPEO.
• Electromyography (EMG): To evaluate muscle function and detect abnormalities.

Management

There is currently no cure for CPEO, and treatment is primarily supportive. Management strategies include:

• Ptosis Surgery: To improve eyelid function and vision.
• Prism Glasses: To alleviate diplopia by correcting eye alignment.
• Physical Therapy: To maintain muscle strength and function.
• Genetic Counseling: For affected individuals and their families to understand the inheritance patterns and risks.

Prognosis

CPEO is a progressive condition, but the rate of progression can vary widely among individuals. While the disorder primarily affects eye muscles, some patients may develop additional symptoms related to mitochondrial dysfunction, such as cardiac conduction defects or sensorineural hearing loss.

Related Pages

• Mitochondrial disease
• Ophthalmoplegia
• Ptosis
• Diplopia
• Mitochondrial myopathy

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