[MELAS syndrome in a five year-old child: clinical, biological and genetic characteristics]

MELAS syndrome is a rare mitochondrial cytopathy; its diagnosis can be difficult.

A 6-month-old boy presented with febrile seizures, possibly due to viral meningitis. At 7 months, he developed myoclonia and "brain attacks" and, subsequently, myoclonical attacks, regression of psychomotor and mental acquisitions, and progressive visual loss. The ratio of lactatorachia/lactacidemia was increased. The molecular genetic analysis showed an heteroplasmic point mutation with A-to-G mutation at nucleotide 3243 of the mitochondrial tRNA(leu) (UUR) gene. He was the second child of a mother having frequent headaches. His great aunt, a sister of his maternal grandmother, was mentally retarded and had frequent epileptic seizures and hemiparesy since her childhood.

Any unusual neurological symptom, particularly when combined with "illegitimate" symptoms, should lead to search for a mitochondrial cytopathy.