Mutations in transfer RNAs have been found to lead to marked mitochondrial energy deficiency and a hindrance of mitochondrial proliferation, and defects in oxidative phosphorylation. Such defects may result in myoclonic epilepsy with ragged-red fibers (MERRF). 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.[4][5]
Mutations in the MT-TG gene has also been associated with familial hypertrophic cardiomyopathy. Familial hypertrophic cardiomyopathy is a heart condition characterized by thickening of the heart, usually in the interventricular septum. Common phenotypes include chest pain, shortness of breath, physical exertion, palpitations, lightheadedness, dizziness and fainting.[6] A family with a transition mutation of 9997T>C in the MT-TG gene exhibited familial hypertrophic cardiomyopathy.[7]