Factsheet
Condition:
MELAS (mitochondrial encephalopathy, lactic acidosis, strokelike episodes)
Inheritance:
Mitochondrial (maternal transmission)
Genetic Etiology:
Mutation in MT-ND5 or MT-TL1, encoding NADH-ubiquinone oxidoreductase chain 5 or mitochondrial tRNA leucine 1, respectively. The most common mutation is A3243G in MT-TL1.
Frequency:
Estimated at approximately 1/6,000 in study done in northern Finland.
Clinical features:
MELAS is a highly variable disorder that affects energy metabolism in multiple tissues. Onset is most commonly in childhood, with seizures, headaches, weakness, stroke-like episodes of transient neurological dysfunction and lactic acidosis, sensorineural hearing loss. There is a gradual loss of cognitive function. Other neurological features can include ataxia and myoclonus.
Management:
Supportive care; administration of coenzyme Q10 and L-carnitine.
Genetic counseling:
Follows pattern of maternal transmission, but with widely variable expression due to heteroplasmy. Molecular genetic testing is available.