MELASによる脳卒中様発作

MELAS: Mitochondrial Encephalomyopathy, Lactic Acidosis and Stroke-Like Episodes

脳卒中は急性に神経症候を呈する疾患であるが，同様の臨床像を呈する疾患がある。ミトコンドリア病はミトコンドリアの代謝障害により細胞へのエネルギー供給に障害を起こす疾患で，詳細な発症機序や治療法についての研究が進められている。MELASはそのうちの1疾患であり，脳梗塞に類似する発症様式や神経症候，画像所見を呈することから，脳卒中診療の際に考慮すべき疾患の1つである。

Abstract

Mitochondrial disease is caused by a deficiency in the energy supply to cells due to mitochondrial dysfunction. Mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS) is a mitochondrial disease that presents with stroke-like episodes such as acute onset of neurological deficits and characteristic imaging findings. Stroke-like episodes in MELAS have the following features: 1) neurological deficits due to localization of lesions in the brain, 2) episodes often accompany epilepsy, 3) lesions do not follow the vascular supply area, 4) lesions are more often seen in the posterior brain than in the anterior brain, 5) lesions spread to an adjacent area in the brain, and 6) neurological symptoms often disappear together with imaging findings, but later relapse. About 80% of patients with MELAS have an A-to-G transition mutation at the nucleotide pair 3243 in the dihydrouridine loop of mitochondrial tRNA^Leu(UUR), which causes the absence of posttranscriptional taurine modification at the wobble nucleotide of mitochondrial tRNA^Leu(UUR) and disrupts protein synthesis. However, the precise pathophysiology of stroke-like episodes is under investigation, with possible hypotheses for these episodes including mitochondrial angiopathy, mitochondrial cytopathy, and neuron-astrocyte uncoupling. With regard to treatment, L-arginine and taurine have recently been suggested for relief of clinical symptoms.