An infant with a mitochondrial A3243G mutation demonstrating the MELAS phenotype

Area of Science:

• Genetics
• Neurology
• Pediatrics

Background:

• Mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) is a common mitochondrial DNA disorder.
• The A3243G mutation is the most frequent genetic cause of MELAS.
• Typical MELAS onset is in school-aged children, with infantile cases being rare.

Observation:

• A 4-month-old infant presented with consciousness disturbances and ventilatory insufficiency.
• Clinical findings included severe lactic acidosis, bilateral brain lesions on MRI, and epileptic discharges on EEG.
• Muscle biopsy revealed ragged-red fibers and succinate dehydrogenase-reactive blood vessels, characteristic of MELAS.

Findings:

• The infant harbored the A3243G mutation, with over 90% of muscle mitochondrial DNA affected.
• The patient's phenotype was consistent with MELAS, despite the early age of onset.
• Pathological muscle findings confirmed the MELAS diagnosis.

Implications:

• This case demonstrates that MELAS can manifest in early infancy with typical clinical features.
• A high percentage of the A3243G mutation may predispose individuals to an earlier onset of MELAS.
• Highlights the importance of considering MELAS in infants presenting with stroke-like episodes and lactic acidosis.