MELAS syndrome (mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes): a case report

Background. MELAS syndrome is a maternally inherited mitochondrial disorder whose cardinal triad — lactic acidosis, seizures, and stroke-like episodes — frequently mimics acute ischaemic stroke. Late, adult-onset presentations are easily missed, delaying disease-specific therapy.
Aim. Through a single clinical case, to outline the diagnostic pathway from a presumptive ischaemic stroke to confirmed mitochondrial encephalomyopathy in a 44-year-old woman, and to map the neuroimaging, neurophysiological, and morphological steps that anchor the diagnosis of MELAS.
Case presentation. A 44-year-old woman was admitted with a working diagnosis of ischaemic stroke after presenting with an upper-left quadrantanopia, blurred near-vision, impaired attention and memory, and a sense of head heaviness. Brain MRI showed cortical laminar necrosis in the right occipital lobe with the subcortical white matter spared — a pattern uncharacteristic of arterial-territory infarction. Lactate dehydrogenase was elevated (450.83 U/L); blood lactate sat at the upper reference limit. Needle EMG documented a reduction in mean motor-unit potential duration. Biopsy of the vastus lateralis muscle revealed fragmentary atrophy, coagulation necrosis of individual fibres, and the ragged-red-fibre pattern of mitochondrial myopathy. Disease-modifying therapy was started — L-arginine, coenzyme Q10, succinic acid, and riboflavin.
Conclusion. Adult-onset MELAS demands deliberate vigilance from the neurologist. Sparing of the subcortical white matter beneath a zone of cortical laminar necrosis, a lesion that ignores arterial territories, a myopathic EMG, and ragged-red fibres on biopsy form a self-reinforcing constellation that supports the diagnosis ahead of molecular confirmation and lets disease-specific treatment begin without delay.

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