Fifty or more pathogenic mtDNA point mutations in tRNA genes have been reported to date. these mutations involve four distinctive clinical conditions that are maternally inherited. These conditions include MELAS, MERRF, a maternally-inherited myopathy and cardiomyopathy (MiMyCa), and a maternally inheritied syndrome of diabetes mellitus and deafness (DAD). Lactic acidosis and RRF commonly accompany these four syndromes.