PADI4 and rheumatoid arthritis: Recently, Song et al. explored polymorphisms in PADI4 and HLA-DRB1 in RA patients and found that recessive genotype of padi4_92 was associated with airway abnormalities and that tryptophan at position 9 of HLA-DRB1 amino acid sequence was strongly associated with RA-ILD in Korean patients with an odds ratio (OR) of 22.89 [43].