This case report concerns a 22-year-old woman who had been diagnosed with systemic lupus erythematosus (SLE). She had intermittent fever, butterfly erythema, photosensitivity, oral ulcers, and multiple arthralgia in the past seven years, but she did not adhere to regular treatments. The edema of the lower extremities and face aggravated in the recent two weeks, so she was admitted to our Department of Rheumatology and Clinical Immunology. Meanwhile, we found she had severe hypertension, the maximal blood pressure was 170/120 mmHg. The patient had high SLE disease activity (the disease activity index score was as high as 23) with blood involvement, acute renal insufficiency, multiple serous effusion and rash. After one week treatments of intravenous methylprednisolone 80 mg daily and other drugs, her conditions made some extent improvement. However, she suffered sudden epileptic attacks. No positive neuro-pathological signs were found, and the blood pressure was up to 190/130 mmHg before the onset of the seizures. Her cerebrospinal fluid (CSF) pressure was 330 mmH₂O, the CSF protein level was normal value, and the white blood cell count was 0 cell/mm ³, with no signs of infection. Cranial MRI showed vasogenic edema at bilateral parietal, occipito-parietal regions, and centrum ovale. We prescribed drugs of decreasing intracranial pressure, intravenous drugs of decreasing blood pressure and midazolam for sedation, without corticosteroid impulse therapy. She recovered consciousness in the next day, without epilepsy recurrence. We eventually diagnosed it as posterior reversible encephalopathy syndrome (PRES), according to the history, laboratory results, imaging featuresand clinical outcome. PRES is a disorder of reversible subcortical vasogenic brain edema in patients with acute neurological symptoms (eg, seizures, encephalopathy, headache, and visual disturbances).PRES is mainly caused by blood pressure changes or endothelial injury, which lead to breakdown of the blood-brain barrier and subsequent brain edema. Most patients have a favourable prognosis.SLE complicated with PRES is not rare, especially in patients with disease activity, hypertension, lupus nephritis and/or renal insufficiency, and use of cytotoxic drugs, early recognition and appropriate treatment remain important. Brainstem involvement, intracranial hemorrhage, renal insufficiency and high disease activity of lupus are risk factors for poor prognosis.