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MELAS: clinical phenotype and morphological brain abnormalities
M Sparaco1, A Simonati, T Cavallaro
1UO di Neurologia con SU, Azienda Ospedaliera, Benevento, Italy.
Acta Neuropathologica
|August 12, 2003
Summary
Mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) shows defective mitochondrial protein synthesis. This study confirms reduced respiratory chain subunit expression in brain tissue, explaining cognitive decline in MELAS patients.
Area of Science:
- Neurology
- Mitochondrial Biology
- Pathology
Background:
- Mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) is a maternally inherited disorder.
- The A3243G mutation in mitochondrial DNA (mtDNA) is a common cause of MELAS.
Observation:
- Autopsy findings from three MELAS patients with the A3243G mutation were analyzed.
- Immunohistochemistry was used to examine respiratory chain subunit expression in brain tissue.
- Mitochondrial abnormalities were focal and most prominent in the cerebral cortex.
Findings:
- All cases exhibited reduced immunocytochemical staining for mtDNA-encoded respiratory chain subunits.
- This confirms defective mitochondrial protein synthesis in MELAS.
- Reduced immunoreactivity was observed in cerebral arterioles, but without clear correlation to lesion distribution.
Implications:
- The findings provide morphological evidence linking mitochondrial dysfunction to cognitive regression in MELAS.
- Focal cerebral lesions in MELAS may be metabolic in origin.
- Multiple pathogenetic mechanisms may contribute to stroke-like episodes in MELAS, potentially related to local ATP demand.