In the moderate BD group, highly expressed proteins were primarily involved in defense response (CRP, ORM1, CFH, C1S, RARRES2, CFI, MST1, KRT1, SAA4, HP, TNC, HPR, IFNW1, KNG1, LOC102723996, C9, SAA1, LBP, APOL1, CFB), acute‐phase response (CRP, ORM1, SAA4, SAA1, HP, HPR, LBP), and immune response (CRP, IGHV3‐43D, CFH, C1S, IGHV3‐11, RARRES2, CFI, MST1, KRT1, IFNW1, ICAM1, VTN, AZGP1, LOC102723996, C9, IGHD, ENPP2, LBP, APOL1, CFB). The gene discussed is C9; the disease is Behcet disease.