A novel de novo mutation of the mitochondrial tRNAlys gene mt.8340G>a associated with pure myopathy

Neuromuscul Disord. 2014 Feb;24(2):162-6. doi: 10.1016/j.nmd.2013.08.004. Epub 2013 Aug 20.


Most patients with mutations in the tRNA(lys) gene (MTTK) present with symptoms from the central nervous system (CNS). We describe a 41-year-old woman with pure myopathy associated with a novel de novo mtDNA mutation, mt.8340G>A, which was heteroplasmic in muscle (53%), blood, urine and mouth epithelial cells (<7%). No other family members, including her mother, carried the mutation. She presented with exercise intolerance from age 9, and since age 20 she experienced ptosis and reduced ocular motility. A muscle biopsy revealed ragged red fibres (10%), no COX negative fibres, and many fibres with central nuclei (30%), indicating ongoing damage and repair. The present case expands the mutational and phenotypic spectrum of diseases associated with mutations in MTTK.

Keywords: MTTK gene; Mitochondrial DNA; Novel mutation; tRNA(lys).

Publication types

  • Case Reports

MeSH terms

  • Adult
  • Base Sequence
  • DNA Contamination
  • DNA, Mitochondrial / genetics*
  • Female
  • Humans
  • Molecular Sequence Data
  • Muscle, Skeletal / pathology
  • Muscle, Skeletal / physiopathology
  • Muscular Diseases / genetics*
  • Muscular Diseases / pathology
  • Muscular Diseases / physiopathology
  • Pedigree
  • Point Mutation*
  • RNA, Transfer, Lys / genetics*


  • DNA, Mitochondrial
  • RNA, Transfer, Lys