The common MELAS mutation A3243G in mitochondrial DNA among young patients with an occipital brain infarct.

The syndrome of mitochondrial encephalomyopathy, lactic acidosis, and strokelike episodes (MELAS) may present with symptoms that resemble a stroke. The strokelike episodes most commonly involve the posterior part of the cerebrum. We identified retrospectively 38 patients with an occipital stroke between ages 18 to 45 years during a 19-year period in a hospital serving as the only neurologic center for a specific population. The common MELAS mutation at the base pair 3243 (A3243G) of the mitochondrial DNA (mtDNA) was analyzed in blood samples. We found four patients (10%) with a clinical or molecular diagnosis of a mitochondrial disorder. Two of the patients carried the A3243G mutation, suggesting frequencies of 6% among patients younger than 45 years of age and 14% among patients younger than 30 years for this mutation. Furthermore, we identified two patients with a clinically definite mitochondrial disorder, and sequencing of the 22 transfer RNA genes revealed the mtDNA mutation A12308G in one patient. Clinical evaluation revealed that occipital stroke was part of a more complex syndrome in these four patients. These population-based findings demonstrate that the A3243G mutation in the mtDNA, and mitochondrial disorders are not uncommon among young patients with occipital stroke.