CPEO associated with a single nucleotide deletion in the mitochondrial tRNATyr gene

In the muscle biopsy of a female patient with chronic progressive external ophthalmoplegia (CPEO), myopathy, and exercise intolerance, the heteroplasmic deletion of a single nucleotide (Delta T5885) in the mitochondrial tRNA tyrosine gene (tRNA Tyr) was found. The mutation was associated with the mitochondrial phenotype of individual muscle fibers, sug- gesting a causal association of Delta T5885 with the mitochondrial disease phenotype. The microdeletion was absent from the patient's and her relatives' blood, indicating a spontaneous somatic origin.