Case report: A 4-months girl presented with bilateral and symmetrical spasms of the trunk and extremities. Interictal-EEG showed hypsarrhythmia. Brain MRI revealed abnormal signal intensity involving basal ganglia and the brainstem. Laboratory study showed increased serum and CSF lactate and ethylmalonic acid (EMA) in blood (6.6 μmol/L) and urine (247.4 mmol/mol creatinine). Skeletal muscle biopsy showed severe COX deficiency. The genetic analysis confirmed ETHE1 mutations1 (p.R163Q4 and the two novel p.Q208deletion and p.I114F aminoacid change). She started carnitine, riboflavin and antiepileptic drugs, and therapy with metronidazole (30 mg/Kg/day) and N-acetylsysteine (100 mg/Kg/day)2. By the age of five months petechiae and acrocyanosis became manifest while rare episodes of diarrhoea were observed. Subsequent EEGs showed progressive pseudorhythmic suppression-burst. The girl died at the age of 9 months after acute metabolic acidosis triggered by respiratory infection. Discussion: The present is the first case of EE with West syndrome at onset while the classical symptoms (recurrent petechiae, acrocyanosis, chronic diarrhoea) appeared later and remained extremely mild. Moreover the severe COX deficiency and lactic acidosis dominated the biochemical picture of our patient, while EMA levels remain relatively low. Finally, metronidazole and N-acetylsysteine proved to be ineffective in preventing the progression of the disease.