Is progressive external ophthalmoplegia inherited ?
Progressive external ophthalmoplegia can have different inheritance patterns depending on the gene involved.  When this condition is caused by mutations in the MT-TL1 gene, it is inherited in a mitochondrial pattern, which is also known as maternal inheritance. This pattern of inheritance applies to genes contained in mtDNA. Because egg cells, but not sperm cells, contribute mitochondria to the developing embryo, children can only inherit disorders resulting from mtDNA mutations from their mother. These disorders can appear in every generation of a family and can affect both males and females, but fathers do not pass traits associated with changes in mtDNA to their children.  When the nuclear genes POLG, SLC25A4, or C10orf2 are involved, progressive external ophthalmoplegia is usually inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder.  Certain mutations in the POLG gene can also cause a form of the condition that is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.  Some mutations in the POLG gene that cause progressive external ophthalmoplegia occur during a person's lifetime and are not inherited. These genetic changes are called somatic mutations.