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[MELAS without ragged-red fibers: a case report].
N Mimaki1, H Hasegawa, I Nonaka
1Department of Pediatrics, South Kurashiki Hospital, Okayama.
No to Hattatsu = Brain and Development
|November 1, 1991
Summary
Mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) can occur without muscle symptoms. Diagnosis relies on identifying strongly SDH-reactive blood vessels (SSV) in frozen sections.
Area of Science:
- Neurology
- Mitochondrial Diseases
- Genetics
Background:
- Mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) is a multisystem disorder.
- Diagnosis typically involves muscle biopsy showing ragged-red fibers (RRF) and mitochondrial dysfunction.
Observation:
- A female patient presented with stroke-like episodes and neurological symptoms but lacked overt muscle weakness.
- Initial muscle biopsies were negative for RRF, and biochemical assays showed normal mitochondrial enzyme activity.
- Mitochondrial abnormalities were identified in smooth muscle cells of intramuscular arterioles via succinic dehydrogenase (SDH) staining and electron microscopy.
Findings:
- The patient was diagnosed with MELAS based on mitochondrial abnormalities in vascular smooth muscle cells, not typical muscle pathology.
- Stroke-like episodes were hypothesized to result from mitochondrial damage in blood vessel walls.
- Strongly SDH-reactive blood vessels (SSV) in frozen sections proved critical for diagnosis.
Implications:
- This case expands the clinical presentation of MELAS, highlighting its potential to manifest without significant muscle involvement.
- SDH staining of intramuscular arterioles offers a valuable diagnostic tool for MELAS, especially in atypical cases.
- Identifying SSV is crucial for accurate MELAS diagnosis and understanding the pathogenesis of stroke-like episodes.