Introduction:
Celiac disease (CD) is one of the most common chronic diseases. Celiac disease has been associated with several autoimmune disorders, but the association with systemic lupus erythematosus (SLE) as a systemic autoimmune disease is still controversial. In this study, we aimed to determine the prevalence of biopsy-proven CD in patients with SLE, and to determine the clinical symptoms and laboratory data in these patients.

Material and methods:
In a cross-sectional study, SLE patients at a referral clinic were evaluated for gastrointestinal symptoms between March and December 2016. Patients were evaluated by a gastroenterologist, and upper gastrointestinal endoscopy with intestinal biopsy was performed if deemed necessary. The clinical symptoms, laboratory data, and endoscopy results were recorded and compared between groups.

Results:
In total, 130 patients were evaluated in this study. Gastrointestinal symptoms were present in 40% of the patients. Endoscopy was performed in all SLE patients with gastrointestinal symptoms. Four patients (3%) were diagnosed as having CD based on biopsy results and response to a gluten-free diet. Anti-endomysium antibody (AEA) was found to be 100% sensitive and 99.2% specific for the diagnosis of CD in SLE patients, and anti-gliadin antibody (AGA) had a 50% sensitivity and 98% specificity. Patients with comorbid CD and SLE were significantly more likely to have diarrhea, abdominal pain, nausea/vomiting, recurrent oral aphthosis, and anemia.

Conclusions:
The results of this study suggest that a significant association is present between CD and SLE. We found a prevalence of 3% for biopsy-proven CD in patients with SLE, which is five times the prevalence of CD in the general population.