DGUOK mutations typically have a hepatocerebral presentation with mtDNA depletion; however, recently chronic progressive external ophthalmoparesis, mitochondrial myopathy, Parkinsonism and multiple mtDNA deletions were also reported in association with recessive DGUOK mutations in some patients (11), while mutations in TK2 have a primarily myopathic manifestation. This evidence concerns the gene DGUOK and Parkinson disease.