Myocarditis is an inflammatory disease of the myocardium accompanied by necrosis of myocytes. The main causes are viral infections. The clinical presentation varies from mild forms to devastating ones which usually begin with trivial symptoms with progression, in some cases, to death. We report the case of an 18 month-old male toddler consulting for asthenia and anorexia for the last 24h and a previous history of respiratory tract infection with high fever in the last week. Upon arrival at the emergency room and during the first hours of admission, physical examination was perfectly normal. Later, his general state gradually deteriorated,with biochemical disturbances (metabolic acidosis, renal failure and hyperglycaemia) and, eventually, a sudden cardiac arrest, with no response to cardiopulmonary resuscitation manoeuvres.