“…An A to G transition at nucleotide position (nt) 3243 in the tRNA Leu (UUR) gene of the mitochondrial DNA, the 3243 mutation, has been found in 80% of MELAS patients [2]. Recently, this mutation has been found in diverse clinical syndromes, including PEO [4], an MERRF/PEO overlap syndrome [10], cluster headache [9], demyelinating polyneuropathy [8], and maternally inherited diabetes and deafness (MIDD) [5]. MIDD is now the most common molecularly defined form of diabetes, with the prevalence being approximately 1.5% of diabetics [3].…”