Mitochondrial encephalopathy with lactic acidosis and stroke-like episodes (MELAS) in a Donegal kindred--clinical features and molecular genetic analysis.

A 19 year old female with a background history of migraine, sensorineural deafness and recent personality change developed a parieto-occipital cerebral infarct. Investigations revealed altered lactate to pyruvate ratios, ragged red fibres in muscle and an A-G point mutation at position 3243 in mitochondrial DNA. Subsequent clinical and molecular genetic analysis of 14 family members in three generations identified 12 affected individuals, two of whom were asymptomatic. Maternal inheritance was confirmed. MEALS is an important but under recognised cause of stroke and seizures in the young. There is insufficient data available to determine if the treatment of asymptomatic individuals retards the onset or reduces the severity of stroke.