Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is the commonest disorder of fatty acid metabolism, with a high incidence of morbidity and mortality at presentation. We report a 16 year old girl with first presentation of MCAD deficiency following an alcoholic binge and subsequent period of starvation. Presentation was as acute encephalopathy progressing to coma. Renal, cardiac and hepatic failures were managed with intensive supportive care including mechanical ventilation, inotropic support, blood products and renal replacement therapy. Diagnosis of MCAD deficiency was confirmed on day 6. The patient was discharged from hospital on day 20 with a mild proximal myopathy, which subsequently resolved. The diagnosis of MCAD deficiency requires a high index of suspicion at all ages. Precipitating factors in later life may include alcohol.