MELAS: clinical features, muscle biopsy and molecular genetics

Arq Neuropsiquiatr. 2009 Sep;67(3A):668-76. doi: 10.1590/s0004-282x2009000400018.


Objective: The aim of the study was to analyze a series of Brazilian patients suffering from MELAS.

Method: Ten patients with MELAS were studied with correlation between clinical findings, laboratorial data, electrophysiology, histochemical and molecular features.

Results: Blood lactate was increased in eight patients. Brain image studies revealed a stroke-like pattern in all patients. Muscle biopsy showed ralled-red fibers (RRF) in 90% of patients on modified Gomori-trichrome and in 100% on succinate dehydrogenase stains. Cytochrome c oxidase stain analysis indicated deficient activity in one patient and subsarcolemmal accumulation in seven patients. Strongly succinate dehydrogenase-reactive blood vessels (SSV) occurred in six patients. The molecular analysis of tRNA (Leu(UUR)) gene by PCR/RLFP and direct sequencing showed the A3243G mutation on mtDNA in 4 patients.

Conclusion: The muscle biopsy often confirmed the MELAS diagnosis by presence of RRF and SSV. Molecular analysis of tRNA(Leu(UUR)) gene should not be the only diagnostic criteria for MELAS.

MeSH terms

  • Adolescent
  • Adult
  • Biopsy
  • Child
  • Child, Preschool
  • Creatine Kinase / blood
  • DNA, Mitochondrial / genetics
  • Female
  • Fructose-Bisphosphate Aldolase / blood
  • Humans
  • Lactates / blood
  • Lactates / cerebrospinal fluid
  • MELAS Syndrome* / diagnosis
  • MELAS Syndrome* / genetics
  • MELAS Syndrome* / pathology
  • Magnetic Resonance Imaging
  • Male
  • Muscle, Skeletal / pathology
  • Mutation / genetics
  • Polymerase Chain Reaction
  • Polymorphism, Restriction Fragment Length
  • Retrospective Studies
  • Tomography, X-Ray Computed
  • Young Adult


  • DNA, Mitochondrial
  • Lactates
  • Creatine Kinase
  • Fructose-Bisphosphate Aldolase