Question: What is (are) Chronic progressive external ophthalmoplegia ?
Answer: Chronic progressive external ophthalmoplegia (CPEO) is a condition characterized mainly by a loss of the muscle functions involved in eye and eyelid movement. Signs and symptoms tend to begin in early adulthood and most commonly include weakness or paralysis of the muscles that move the eye (ophthalmoplegia) and drooping of the eyelids (ptosis). Some affected individuals also have general weakness of the skeletal muscles (myopathy), which may be especially noticeable during exercise. Muscle weakness may also cause difficulty swallowing (dysphagia). 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. CPEO can occur as part of other underlying conditions, such as ataxia neuropathy spectrum and Kearns-Sayre syndrome. These conditions may not only involve CPEO, but various additional features that are not shared by most individuals with CPEO.
Source: GARD

Question: Is Chronic progressive external ophthalmoplegia inherited ?
Answer: Is chronic progressive external ophthalmoplegia inherited? 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). 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. 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. The risk for other family members to be affected depends on the genetic cause and the inheritance pattern in the family.
Source: GARD