Aside from hereditary factors and sexual hormones, 3, 4 environmental factors are also among the main factors in the induction of SLE. 5 Considering environmental factors, UVinduced SLE has attracted much attention. UV light may induce auto-antigenic apoptotic particles resulting in DNA peroxidation and up-regulation of some cytokines and chemotactic factors, resulting in SLE or its recurrence. 6 Based on this, the incidence of SLE in the summer and the autumn, when there is stronger sunlight and stronger UV rays, should be higher. However, there have been different reports regarding seasonal distribution of active SLE. [7] [8] [9] [10] [11] [12] Differing results may be due to the fact that patients lived in various geographical locations, the sample sizes were small, and SLE was stable in the patients who were being followed-up and being treated with drugs, which failed to objectively reflect seasonal distribution of active SLE.