When we arranged the top 50 up-regulated genes according to decreasing fold-change values (Fig. 1a) or the bottom 50 down-regulated genes according to increasing fold-change values (Fig. 1b), we found several genes were up-regulated (>3.0-fold, including PCDH18, BBS5, and PP2A), or down-regulated (<20-fold, including RPS4Y1, DDX3Y and RPS4Y2) in many BD patients. This evidence concerns the gene PCDH18 and Behcet disease.