Progressive external ophthalmoplegia characterized by multiple deletions of mitochondrial DNA: unraveling the pathogenesis of human mitochondrial DNA instability and the initiation of a genetic classification

Neuromolecular Med. 2003;3(3):129-46. doi: 10.1385/NMM:3:3:129.


Over the last decade, many sporadic and familial cases have been reported with multiple deletions of mitochondrial DNA (mtDNA) in postmitotic tissues. Most patients suffer from progressive external ophthalmoplegia (PEO) and may have a nuclear gene defect that predisposes to the accumulation of mtDNA deletions. Recently, positional cloning has led to the discovery of mutations in four such nuclear genes. Some mutations are dominant and others recessive. In all autosomal mutations, defective mtDNA replication and/or repair are probably responsible for the generation of secondary mtDNA deletions. There are also data suggestive of a prominent pathogenic role for disturbed nucleotide metabolism. We here present a tentative genotype-phenotype correlation. Since clinical presentations are heterogeneous and overlap with different previously described clinical syndromes, we advocate the use of a genetic, instead of a clinical, classification of disorders with multiple mtDNA deletions.

Publication types

  • Review

MeSH terms

  • Animals
  • Cell Respiration / genetics
  • DNA Replication / genetics
  • DNA, Mitochondrial / genetics*
  • Gene Deletion*
  • Humans
  • Mutation / genetics*
  • Nucleotides / genetics
  • Nucleotides / metabolism
  • Oculomotor Muscles / metabolism*
  • Oculomotor Muscles / pathology
  • Oculomotor Muscles / physiopathology
  • Ophthalmoplegia, Chronic Progressive External / classification
  • Ophthalmoplegia, Chronic Progressive External / genetics*
  • Ophthalmoplegia, Chronic Progressive External / metabolism*


  • DNA, Mitochondrial
  • Nucleotides