Late onset of stroke-like episode associated with a 3256C→T point mutation of mitochondrial DNA

Abstract Mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) are usually associated with the common 3243A→G mutation of mtDNA. Onset of stroke-like episodes usually occurs before age 30. We report a patient with late onset MELAS harboring a rare 3256C→T mutation in the tRNA Leu(UUR) gene of mtDNA. The patient presented with a stroke-like episode at age 36. MRI showed a stroke-like lesion in the right parietooccipital brain region. Proton MR spectroscopy showed elevated lactate concentrations in the lesion (8.4 mmol/l), and in the mid-occipital region (2.3–3.2 mmol/l) that appeared normal on MRI. Further tests revealed evidence of a severe oxidative defect of muscle metabolism as well.