MELAS SYNDROME WITH MITOCHONDRIAL TRNA(LEU(UUR)) GENE MUTATION IN A CHINESE FAMILY

The clinical features of a patient in a Chinese family with mitochondr ial myopathy, encephalopathy, lactic acidosis, and stroke-like episode s (MELAS syndrome) are reported. The study revealed that hearing and v isual impairments and miscarriages may be early clinical presentations in MELAS. A heteroplasmic A to G transition in the tRNA(Leu(UUR)) gen e was noted at the nucleotide pair 3243 in the mitochondrial DNA of mu scle, blood, and hair follicles of the proband and his maternal relati ves. Quantitative analysis of the mutated mitochondrial DNA revealed v ariable proportions in different tissues and subjects of maternal Line age in the family Muscle tissue contained a higher proportion of the m utant mitochondria than other tissues examined. The function of the re productive system of the proband seems to be impaired. In one clinical ly healthy sibling, the 3243rd point mutation was found in sperm mitoc hondrial DNA, although sperm motility was not affected. It seems that biochemical defects in mitochondrial respiration and oxidative phospho rylation are tissue specific expressions of the 3243rd point mutation in the mitochondrial DNA of the affected target tissues.