Exercise intolerance, muscle pain and lactic acidaemia associated with a 7497G>A mutation in the tRNASer(UCN) gene

J Inherit Metab Dis. 2003;26(6):593-600. doi: 10.1023/a:1025960300710.


A 13-year-old girl with non-familial exercise intolerance, muscle pain and lactic acidaemia underwent a muscle biopsy for suspected mitochondrial disease. Muscle morphology showed 25% ragged-red fibres and 80% COX-negative staining. Enzymatic activities of mitochondrially co-encoded respiratory chain enzymes (complexes I, III, and IV) were decreased in muscle but normal in cultured skin fibroblasts. mtDNA analysis revealed the presence of the 7497G>A mutation in the tRNASer(UCN) gene, homoplasmic in skeletal muscle and 90% in leukocytes. Analysis of the mother's mtDNA showed 10% heteroplasmy in blood. It may be concluded that the 7497G>A mutation is associated with a muscle-only disease presentation for which high levels of mutated mtDNA are required. Exercise intolerance and muscle pain in otherwise normal children warrants further mitochondrial evaluation.

Publication types

  • Case Reports

MeSH terms

  • Acidosis, Lactic / complications
  • Acidosis, Lactic / genetics*
  • Adolescent
  • Brain / pathology
  • DNA, Mitochondrial / genetics
  • Electrocardiography
  • Electroencephalography
  • Electromyography
  • Evoked Potentials, Auditory / physiology
  • Evoked Potentials, Somatosensory / physiology
  • Exercise Tolerance / genetics*
  • Female
  • Fibroblasts / enzymology
  • Humans
  • Magnetic Resonance Imaging
  • Muscle, Skeletal / enzymology
  • Muscle, Skeletal / pathology
  • Muscular Diseases / genetics*
  • Muscular Diseases / pathology
  • Oxidation-Reduction
  • Pain / complications
  • Pain / genetics*
  • RNA, Transfer, Ser / genetics*
  • Reverse Transcriptase Polymerase Chain Reaction


  • DNA, Mitochondrial
  • RNA, Transfer, Ser