Case Report

Acta Neuropathologica

, Volume 90, Issue 3, pp 328-333

Tissue distribution and disease manifestations of the tRNALys A»G(8344) mitochondrial DNA mutation in a case of myoclonus epilepsy and ragged red fibres

  • Anders OldforsAffiliated withDepartment of Pathology, Sahlgrenska Hospital
  • , Elisabeth HolmeAffiliated withDepartment of Clinical Chemistry, Sahlgrenska Hospital
  • , Már TuliniusAffiliated withDepartment of Paediatrics, East Hospital
  • , Nils-Göran LarssonAffiliated withDepartment of Clinical Chemistry, Sahlgrenska Hospital

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Abstract

This man with myoclonus epilepsy and ragged red fibres (MERRF) syndrome due to the tRNALys A»G(8344) mutation of mitochondrial DNA (mtDNA) died of bronchopneumonia at 18 years of age. He had progressive clinical symptoms from 6 months of age manifesting as ataxia, myoclonic seizures, and muscle weakness. A postmortem examination revealed 91–99% mutated mtDNA in all 32 examined tissue samples, including various organs and different brain regions. The brain appeared without macroscopic changes, but microscopic examination showed degeneration with loss of nerve cells and gliosis affecting the globus pallidus, substantia nigra, red nucleus, dentate nucleus, inferior olivary nucleus, cerebellar cortex, and the spinal cord. Skeletal muscle showed cytochrome c oxidase deficient muscle fibres with proliferation of mitochondria. In addition to pathological changes of muscle and brain there were few morphological changes that could be attributed to his mitochondrial disease. These data support the concept that in patients with the tRNALys A»G(8344) mutation who are manifesting disease there are high levels of mutated mtDNA in all tissues, but only some tissues and brain regions are vulnerable.

Key words

Myoclonus epilepsy Mitochondrial enoephalomyopathy Mitochondrial DNA Mutation Neuropathology