A Reye Like Syndrome case occurred in a twelve year-old little girl with a previous familiar history is reported. The little patient was admitted in the pediatric ward for fever, vomiting and aspecific respiratory symptoms and developed very quickly a severe metabolic acidosis, alterations of consciousness, hypoxia, tissular hypoperfusion, multiple organ failure (MOF) and a fatal outcome. The postmortem diagnosis pointed out a methyl malonic acidaemia, a fairly frequent cause of acute metabolic distress, which may occur also in prepuberal age. The correct diagnostic and therapeutic approach of these cases is stressed since they need a prompt and careful monitoring in intensive care unit and a close cooperation among pediatricians, intensive care specialists and the nearest centre for the study of metabolic diseases.