Introduction: The syndrome of chronic progressive external ophthalmoplegia (CPEO) is a mitochondrial disease characterized by ptosis and ophthalmoplegia has that has been associated to the presence of large deletion, single or multiple, in the mitochondrial DNA of skeletal muscle.
Case report: We report a familiar case of chronic progressive external ophthalmoplegia of maternal inheritance that began at birth, and developed with slow progression but with no multisystemic involvement. Non of the affected individuals had ragged-red fibers in skeletal muscle. Genetic analysis of mitochondrial DNA revealed the presence of a single deletion of 4,977 bp that encompasses the nucleotide positions 8,482 to 13,460, flanked by a direct repeat sequence.
Conclusions: The amount of deleted mitochondrial DNA (15%) in this patient's muscle suggests, even if the percentage of the mutation is low, that this deletion is the molecular cause of the phenotypic presentation of this patient. This is one of the few cases described in the literature of CPEO maternally inherited.