Mitochondrial encephalomyopathy with cytochrome c oxidase deficiency caused by a novel mutation in the MTCO1 gene

Mitochondrion. 2014 Jul;17:101-5. doi: 10.1016/j.mito.2014.06.003. Epub 2014 Jun 20.


Cytochrome c oxidase (COX) deficiency is one of the most common respiratory chain deficiencies. A woman was presented at the age of 18y with acute loss of consciousness, non-convulsive status epilepticus, slow neurological deterioration, transient cortical blindness, exercise intolerance, muscle weakness, hearing loss, cataract and cognitive decline. Muscle biopsy revealed ragged-red fibers, COX negative fibers and a significant decreased activity of complex IV in a homogenate. Using next generation massive parallel sequencing of the mtDNA, a novel heteroplasmic mutation was identified in MTCO1, m.7402delC, causing frameshift and a premature termination codon. Single fiber PCR showed co-segregation of high mutant load in COX negative fibers. Mutation in mitochondrially encoded complex IV subunits should be considered in mitochondrial encephalomyopathies and COX negative fibers after the common mtDNA mutations have been excluded.

Keywords: Cytochrome c oxidase; Encephalomyopathy; MTCO1; Mitochondrial DNA.

Publication types

  • Case Reports

MeSH terms

  • Adolescent
  • Biopsy
  • Codon, Nonsense
  • Cytochrome-c Oxidase Deficiency*
  • DNA, Mitochondrial / chemistry
  • DNA, Mitochondrial / genetics
  • Electron Transport Complex IV / genetics*
  • Female
  • Frameshift Mutation
  • High-Throughput Nucleotide Sequencing
  • Humans
  • Mitochondrial Encephalomyopathies / diagnosis*
  • Mitochondrial Encephalomyopathies / genetics*
  • Mitochondrial Encephalomyopathies / pathology
  • Muscles / pathology
  • Mutation*


  • Codon, Nonsense
  • DNA, Mitochondrial
  • Electron Transport Complex IV
  • cytochrome c oxidase subunit I, human