RESUMEN
Today, with the advent of new medications, treatment of Ulcerative colitis [UC] has been markedly improved. Immunosuppressive drugs used in therapy predispose patients to opportunistic infections. A 22-year-old woman was admitted to emergency department due to acute exacerbation of UC and decreased level of consciousness. She was under treatment with 5-aminosalicylate, prednisolone and azathioprine. In neurological evaluation, patient had cerebral herniation. Non-contrast CT scan revealed multiple hemorrhagic areas in both frontal lobes. Right frontal craniotomy was performed emergently. Histopathologic evaluation of brain tissue was reported as "Herpes simplex encephalitis". Polymerase chain reaction [PCR] assay was also positive for HSV DNA. Immunosuppressive drugs such as azathioprine have a pivotal role in the treatment of resistant and/or severe cases of UC. Prevalence of infectious complications was reported to be 7.4%, 1.8% of which were severe [including herpes zoster encephalitis] .Our review of literature indicates that no case of herpes simplex encephalitis following immunosuppressive therapy for UC has been reported