A 15-month-old female child presented with sudden onset cough and hyperventilation along with evidence of metabolic acidosis. She had past history of recurrent vomiting, episodes of abnormal posturing, difficulty in deglutition and regression of milestones since 12 months of age. CT scan of the brain revealed hypodense lesions in bilateral basal ganglia and on MRI there were T2 hyperintensities in bilateral lentiform nuclei, caudate nuclei, thalamus, red nuclei and dentate nuclei. Biochemical examination revealed persistently elevated serum lactate levels with high lactate/pyruvate ratio. Resuscitative measures were of no avail and the child succumbed to the illness on the second day of admission. Neuropathological examination at autopsy demonstrated marked spongiosis, focal necrosis, endothelial proliferation, reactive astrogliosis and extensive demyelination involving bilateral basal ganglia, midbrain and spinal cord which were typical of Leigh's sub acute necrotizing encephalomyelopathy.