Mutations in MT-TT have been associated with myoclonic epilepsy with ragged-red fibers (MERRF), and cause mitochondrial energy deficiencies and reduced proliferation leading to oxidative phosphorylation. Myoclonic epilepsy with ragged-red fibers (MERRF) is a rare mitochondrial disorder that affects many parts of the body, particularly the muscles and nervous system. In most cases, the signs and symptoms of this disorder appear during childhood or adolescence. The features of MERRF vary widely among affected individuals, even among members of the same family. Common clinical manifestations include myoclonus, myopathy, spasticity, epilepsy, peripheral neuropathy, dementia, ataxia, atrophy and more.[6][7] In addition, mutations have also been linked to lethal infantile mitochondrial myopathy, Parkinson's disease associated with a 15950G>A mutation,[8] and a 15923A>G mutation found to result in an unconfirmed heart disease.[9][10]
MT-TT mutations result in complex IV deficiency of the mitochondrial respiratory chain, also known as the cytochrome c oxidase deficiency. Cytochrome c oxidase deficiency is a rare genetic condition that can affect multiple parts of the body, including skeletal muscles, the heart, the brain, or the liver. Common clinical manifestations include myopathy, hypotonia, and encephalomyopathy, lactic acidosis, and hypertrophic cardiomyopathy.[11] A 15915G>A mutation was found in a patient with cytochrome c oxidase deficiency with accompany symptoms of seizures, progressive hearing loss and muscle weakness.[12]
