A tRNAAla mutation causing mitochondrial myopathy clinically resembling myotonic dystrophy

Apart from large scale mtDNA rearrangements and common point mutations in mt tRNA genes, pathogenic mutations affecting structural genes of mtDNA encoded respiratory chain subunits have been reported as well. 1 Pathogenic tRNA mutations can affect translation of respiratory chain (RC) complexes that are partly encoded by the mtDNA, that is, complexes I, III, and IV. The electrophysiological evidence of myotonia prompted us to consider myotonic dystrophy or glycogen storage disorder type 2 (Pompe's disease). [...]an open muscle biopsy from the M biceps brachii was carried out. Another possible mechanism is apoptosis as it has been repeatedly suggested in mitochondrial disorders. 28- 30 Apoptotic features, mainly localised to cytochrome c oxidase negative fibres, were observed in muscle fibres of patients carrying a high percentage of single mt DNA deletions (>40%) and of different tRNA point mutations (>70%).