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Updated: Jun 20, 2026

Immunolabelling Myofiber Degeneration in Muscle Biopsies
Published on: December 5, 2019
MELAS: clinical features, muscle biopsy and molecular genetics
Paulo José Lorenzoni1, Rosana H Scola, Cláudia S Kamoi Kay
1Internal Medicine Department, Universidade Federal do Paraná, Curitiba, PR, Brazil.
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.
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