Pathogenic mtDNA mutations causing mitochondrial myopathy: The need for muscle biopsy.
Hardy SA., Blakely EL., Purvis AI., Rocha MC., Ahmed S., Falkous G., Poulton J., Rose MR., O'Mahony O., Bermingham N., Dougan CF., Ng YS., Horvath R., Turnbull DM., Gorman GS., Taylor RW.
Pathogenic mitochondrial tRNA (mt-tRNA) gene mutations represent a prominent cause of primary mitochondrial DNA (mtDNA)-related disease despite accounting for only 5%-10% of the mitochondrial genome.(1,2) Although some common mt-tRNA mutations, such as the m.3243A>G mutation, exist, the majority are rare and have been reported in only a small number of cases.(3) The MT-TP gene, encoding mt-tRNA(Pro), is one of the less polymorphic mt-tRNA genes, and only 5 MT-TP mutations have been reported as a cause of mitochondrial muscle disease to date (table e-1 at Neurology.org/ng, P6-10). We report 5 patients with myopathic phenotypes, each harboring different pathogenic mutations in the MT-TP gene, highlighting the importance of MT-TP mutations as a cause of mitochondrial muscle disease and the requirement to study clinically relevant tissue.