Adult-onset chronic progressive external ophthalmoplegia with mitochondrial myopathy is a rare mitochondrial condition that begins in adulthood. It is characterized by a gradual weakening of the muscles around the eyes, which can lead to difficulty moving them. People with this condition may experience exercise intolerance and overall muscle weakness. In addition to the eye muscle problems, some individuals may have signs of spinocerebellar ataxia, such as an unsteady walk or slurred speech, and mild motor peripheral neuropathy. There have also been reports of respiratory insufficiency in some cases. This summary is based on available information from the provided sources.

Common signs include progressive difficulty in moving the eyes, muscle weakness, and exercise intolerance. Some individuals may also experience problems with balance and speech, as well as mild nerve issues in the limbs. Breathing difficulties have been noted in some cases.

This condition is classified as a mitochondrial disease, meaning that the energy-producing parts of cells are affected. Specific genetic causes have not been identified, and no known genes have been linked to the condition so far. Associated genes include RNASEH1.