Posterior reversible encephalopathy syndrome (PRES) in patients with systemic 
lupus erythematosus (SLE) has been recognized increasingly. This study aimed to 
determine the prevalence, clinical features, brain imaging findings, outcomes, 
and associated factors of PRES in Thai SLE patients. SLE patients with PRES were 
identified from the lupus cohort of Chiang Mai University. Controls were SLE 
patients with a hospital number close to and actually had SLE diagnosis within 5 
years of the case (case:control ratio = 1:4). Of 1,332 SLE patients, 30 episodes 
of PRES were identified in 24 female SLE patients (prevalence 1.80%). The mean ± 
SD age at SLE diagnosis and at onset of PRES was 25.02 ± 13.78 and 28.31 ± 
12.61 years, respectively. Seizure was the most common presenting symptom, as 
seen in 28 episodes, followed by acute severe headache in 17, alteration of 
consciousness in 17, nausea and vomiting in 10, blurred vision in 11, and 
hemiparesis in 3. Abrupt increase in blood pressure and active nephritis were 
seen in 29 and 26 of the episodes, respectively. Urine protein/creatinine ratio 
> 1.00 (OR 15.72, 95% CI 3.12-79.12, p = 0.001) and hemoglobin < 10 gm/dL (OR 
5.12, 95% CI 1.37-19.15, p = 0.015) were associated factors for developing PRES. 
During the observation period, 7 patients in the PRES group and 8 in the control 
group died (p = 0.015). PRES was uncommon in SLE patients, but associated with a 
high mortality rate. Active nephritis and anemia were associated factors of PRES 
in Thai SLE patients.