To assess the possibility of PFDN5 and anti-PFDN5 as a biomarker of disease activity in AS, we also analyzed the correlation of PFDN5 and anti-PFDN5 antibody with Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) in the Korean cohort (data not shown in the Results). This evidence concerns the gene PFDN5 and spondylitis.