ERAP1 and ankylosing spondylitis: Indeed, plasma levels of ERAP1 and ERAP2 have been recently reported as markers of disease severity in inflammatory bowel diseases, preeclampsia, ankylosing spondylitis, and hepatitis B infection (Ferreira et al., 2021; Liu et al., 2022; Bai et al., 2024; You et al., 2024).