Mitochondrial encephalomyopathy lactic acidosisand stroke-like episodes (melas) with the A3243G mutation of the tRNA Leu(uur) gene of mtDNA in native American haplogroup B2

Introduction. Mitochondrial encephalopathy, lactic acidosis and cerebrovascular accident syndrome (MELAS) is, from the clinical point of view, one of the best studied mitochondrial multisistemic disorders. This disease has mainly been associated to the mitochondrial DNA (mtDAA) mutation A3243G located in the tRNA(Leu(UUR)) gene. Although a relation between European haplogroups and the presence of the 3243 mutation has not been described, nothing is known about the presence of this mutation in native American haplogroups. Case report. A 12 year-old female Mexican patient diagnosed with MELAS is reported. Besides neurological, biochemical and cytological examination, we also analyzed the particular mtDAA mutations related to MELAS and the whole genome was sequenced to determine the mitochondrial haplogroup. The A3243G mutation was detected in the patient and maternal relatives (mother and sibblings, all of them asymthoniatic). The genotype corresponds to the native American haplogroup B2 and contains two private non-synonymous polymorfisms. Conclusion. All the members of the family studied present different percentage of the A3243G mutation, being the patient who presented the highest value. The mtDNA genotype corresponds to the native American haplogroup B2 and the private polymorphisms do not confer any phenotypic modification in MELAS syndrome.