Purpose: Mitochondrial T9957C mutations have been reported in patients with nonarteritic ischemic optic neuropathy and seizures and in patients with mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes. However, thus far, this mutation has not been reported in patients with chronic progressive external ophthalmoplegia (CPEO).
Case report: Here we report a female patient with CPEO and agenesis of the corpus callosum. Although no ragged-red fibers were found upon muscle biopsy, sequencing of the entire mitochondrial DNA genome was done.
Results: The molecular genetic study revealed a nonsynonymous mitochondrial T9957C mutation. a new genotype of CPEO was identified with varied clinical presentations. Although the effect of the nuclear genome remains unknown, we believe that the nonsynonymous mitochondrial DNA (mtDNA) T9957C mutation may have a role in the clinical manifestations of this patient.
Conclusion: This study extends the phenotype of T9957C mtDNA mutation.