Severe acute disseminated encephalomyelitis associated with parainfluenza 3 infection.Case report Disseminated encephalomyelitis (ADEM) is an infrequent condition with considerable morbidity and mortality in adult patients.It requires a high level of suspicion and diagnosis emerges by gathering clinical information, laboratory exams and images studies.ADEM is related to an immunological phenomena occurring after a bacterial/ viral infection or recent vaccination.Glucocorticoids are the first line treatment, reserving immunoglobulins and plasmapheresis to refractory cases.We report a male patient aged 25, with ADEM associated to parainfluenza 3 virus respiratory infection that required mechanical ventilation and that had a complete recovery only after plasmapheresis.