Meanwhile, multiple HLA-related gene variants also play essential roles in BD, including variants in the class II major histocompatibility complex transactivator (CIITA), endoplasmic Reticulum Aminopeptidase 1 (ERAP1) and the major histocompatibility complex class I chain related gene A (MICA) (64). The gene discussed is ERAP1; the disease is Behcet disease.