TWNK and mitochondrial DNA depletion syndrome 7 (hepatocerebral type): The dominant TWNK variants cause progressive external ophthalmoplegia with mitochondrial DNA deletions, autosomal dominant 3 (PEOA3), while the recessive variants cause mitochondrial DNA depletion syndrome 7 (MTDPS7) and Perrault syndrome 5 (PRLTS5) [1].