Chronic progressive external ophthalmoplegia (CPEO), which is an inherited mitochondrial disease associated with the mutation or deletion of mitochondrial DNA (mtDNA), is induced by nuclear DNA mutations in the DNA polymerase gamma (POLG) gene [1], but is rarely induced by mtDNA mutations. Here we report a unique Japanese CPEO family with a novel homozygous m.14819 T > G (p. S25A) substitution accompanied by an mtDNA deletion (m.8483₋13,459, del 4977), showing bilateral ptosis and muscle weakness in the proband and the proband’s mother, but not in the brother.

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