MPO and inflammatory bowel disease: While anti-Myeloperoxidase (MPO) and anti-Proteinase 3 (PR3) are considered the major components of the ANCA group, antibodies against other components such as bacterial permeability-increasing protein (BPI), elastase, cathepsin, lysozyme, and lactoferrin have all been described in inflammatory conditions which include; inflammatory rheumatic diseases, inflammatory bowel disease, etc. [30–33].