A comparative morphological study in 33 cases of respiratory chain encephalomyopathies.

Mitochondrial encephalomyopathies (ME) are clinically and genetically heterogeneous syndromes ranging from pure myopathies to complex multisystem disorders. This phenotypic and genotypic variability, coupled with the lack of a laboratory gold standard marker for the diseases, makes diagnosis a challenging process. Mitochondrial DNA analysis and biochemical assay of muscle homogenates are quite specific diagnostically but have low sensitivity in unselected cases suspected of ME.