A 6-month-old girl with familiar history of two dead sisters few months old, was admitted to the Hospital with a neurological process. After her admission progressively worsened until her death. The patient had clinical manifestation of proximal tubular acidosis. Levels of lactic and piruvic acid were normal. Necropsic study was compatible with the diagnoses of subacute necrotizing encephalomielopathy of Leigh syndrome.