ObjectivesTo investigate serum levels of vitamin D and its effect on microRNA 22 and 125b gene expression in Behçet’s disease (BD) patients and to evaluate their relation to clinical characteristics and disease activity.MethodsFifty-one BD patients and 45 matching controls were studied. Disease activity was assessed using BD Current Activity Form (BDCAF). Serum vitamin D3 was measured by ELISA. MicroRNAs were assayed by reverse transcription- quantitative polymerized chain reaction (RT-qPCR).ResultsPatients mean age was 34.3±8.6 years and disease duration 65.3±52.4 months. The BDCAF was 2.4±1.3. Vitamin D level was significantly lower (29.7±14.4 ng/ml) in patients than in control (40.1±17.8 ng/ml)(p<0.001) especially males (25.8±7.5 ng/ml) compared to females (48±23.7 ng/ml)(p<0.001). There was no relation between 25(OH)D levels and disease activity or with the presence of clinical manifestations. There was a 3.8±1.5 fold increase in miRNA125b while miR-22 showed no significant difference (0.38±0.46) but was significantly reduced in those receiving steroids (0.21±0.27) compared to those not (0.66±0.58)(p=0.003). There was no significant difference in the frequency of miR-22 or miR-125 expression according to the presence of clinical manifestations, medications received or disease activity. The fold change in miR-125b significantly correlated with vitamin D (r=0.54,p<0.001) but not with BDCAF (p=0.64).ConclusionsVitamin D level is decreased in BD patients and significantly correlated with the fold change of miR-125b especially in males thus representing a possible therapeutic target. The miR-22 expression did not change but was notably downregulated by steroids. Further longitudinal studies on a larger sample are recommended to validate the present results.Disclosure of InterestNone declared