The association of Ankylosing Spondylitis with aminopeptidases located either inside the endoplasmic reticulum (ER)—such as ERAP1 [47,48,54,56,64,73,74,75,76,77,78,79,80,81,82,83,84], ERAP2 [28,50], and LNPEP [28,47]—or in the cytoplasm—specifically NPEPPS [28,85]—highlights the importance of this process. Here, ERAP2 is linked to ankylosing spondylitis.