Abstract： To the Editor:Posterior reversible encephalopathy syndrome (PRES) is a rare condition of the central nervous system (CNS).Clinically,it can present with headache,blurred vision,seizures,or coma.The diagnosis of PRES is based on the classic radiologic imaging studies at occipital and parietal lobes in the subcortical white matter,and sometimes in the cortex.Hypertensive encephalopathy,eclampsia,immunosuppressive agents,and cytotoxic drugs can cause PRES.A patient with PRES may recover without sequela after removal of the causative factors.Notably,uncertainty in diagnosis and delay in treatment would have probably aggravated CNS injuries or death.However,the underlying mechanism of the disease remains unclear and controversial.