Childhood MELAS syndrome presenting with seizure and cortical blindness: a case report.

An 11-year-old boy presented with seizure and cortical blindness. A T1 weighted magnetic resonance image of the brain showed high signal intensity in the bilateral corpus striatum and long T1 and T2 changes in the bilateral occipital and cerebellar hemispheric regions. Increased cerebrospinal fluid lactate concentration of 56.7 mg/dl and blood lactate concentration of 34.2 mg/dl were also noted. A muscle biopsy obtained from the quadriceps femoris muscle showed the presence of ragged red fibers and mitochondrial DNA (mtDNA) analysis showed an A-->G mutation at nucleotide position 3243. MtDNA analysis of the patient's mother revealed the same mutation. These findings indicated MELAS syndrome (mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes).