Mitochondrial myopathy and complex III deficiency in a patient with a new stop-codon mutation (G339X) in the cytochrome b gene

J Neurol Sci. 2003 May 15;209(1-2):61-3. doi: 10.1016/s0022-510x(02)00462-8.


A 19-year-old woman complained of life-long exercise intolerance and had chronic lactic acidosis. Neurological examination was normal, but muscle biopsy showed cytochrome c oxidase-positive fibers and marked complex III deficiency. Sequence analysis showed a novel stop-codon mutation (G15761A) in the mitochondrial DNA (mtDNA)-encoded cytochrome b gene, resulting in loss of the last 41 amino acids of the protein. By PCR/restriction fragment-length polymorphism (RFLP) analysis, the G15761A mutation was very abundant (73%) in the patient's muscle, barely detectable (less than 1%) in her urine, and absent in her blood; it was also absent in muscle, urine and blood from the patient's mother. This mutation fulfills all accepted criteria for pathogenicity.

Publication types

  • Case Reports
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Acidosis, Lactic / diagnosis
  • Acidosis, Lactic / etiology
  • Adult
  • Biopsy
  • Chronic Disease
  • Codon, Nonsense*
  • Cytochrome b Group / genetics*
  • DNA, Mitochondrial / genetics
  • Electron Transport Complex III / deficiency*
  • Electron Transport Complex III / genetics
  • Exercise Tolerance / genetics
  • Female
  • Humans
  • Mitochondrial Myopathies / complications
  • Mitochondrial Myopathies / diagnosis*
  • Mitochondrial Myopathies / pathology
  • Muscle, Skeletal / enzymology
  • Muscle, Skeletal / pathology
  • Polymerase Chain Reaction
  • Polymorphism, Restriction Fragment Length
  • Sequence Deletion


  • Codon, Nonsense
  • Cytochrome b Group
  • DNA, Mitochondrial
  • Electron Transport Complex III