Mild encephalitis with reversible splenial (MERS) lesion syndrome due to influenza B virus

We describe a 16-year-old boy with mild encephalitis with reversible lesions in the white matter and splenium of corpus callosum as a complication of an influenza B virus infection. Although more common in Asiatic children, it can also occur in Caucasian children and adults. There are several possible causes, including metabolic disorders, hypertension and infection, and the prognosis is usually good, even without treatment.