Chronic Progressive External Ophthalmoplegia

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The cardinal manifestation of Chronic Progressive External Ophthalmoplegia (CPEO) is progressive extraocular weakness. In relation to Musculosokeletal Medicine, chronic pain affects the majority of those with this disorder, with the proximal lower limbs and head being the most common sites. Pain in the spine and calves are the next most common sites. Chronic fatigue and depression are also common.


The nuclear gene called POLG is responsible for encoding the catalytic subunit of the only known mitochondrial DNA polymerase in animals. When there are mutations in this gene, the replication of mtDNA is affected, leading to large-scale mtDNA deletions, depletion of mtDNA copy number, and point mutations in mtDNA. These mutations cause a wide range of clinical symptoms. In adults, the most common manifestation of POLG mutations is chronic progressive external ophthalmoplegia (CPEO) accompanied by the accumulation of multiple mtDNA deletions.

POLG mutations can be inherited in an autosomal dominant or recessive manner, or they can arise spontaneously as dominant mutations. The primary diagnosis for CPEO caused by mitochondrial disease is a single mtDNA deletion or the m.3243A > G point mutation in mtDNA. Other possible causes of CPEO include oculopharyngeal muscular dystrophy, myasthenia gravis, congenital myopathy, and muscular dystrophies.


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