[Progressive external ophthalmoplegia with extensive mitochondrial DNA deletion].

We report extensive deletion of muscle mitochondrial DNA and ophthalmological findings in a patient with progressive external ophthalmoplegia. The patient was a twenty-nine-year-old female who had suffered from slowly progressive external ophthalmoplegia for ten years. No abnormal finding was observed in the funduscopic examination, but fluorescein angiography showed mottled hyperfluorescence. The final rod threshold for the dark adaptation testing was slightly elevated. The flash electroretinogram showed a slightly attenuated b wave. Ragged-red fibers were observed in muscle biopsies. A biochemical and histochemical study showed that cytochrome c oxydase activity was reduced. The length of deletion of the mitochondrial DNA, determined by polymerase chain reaction, was 4977 base pairs, flanked by a 13-base pair direct repeat.