PADI4 and interstitial lung disease: Taking into account the PAD4 proteins, the SNVs in PAD that encode them, and the risk factors (environmental exposures) of individuals with the diseases, PAD4 levels increased in individuals with RA-ILD that are homozygous at a minor allele associated with a risk of RA-ILD, the rs11203367-CC, rs1748033-TT, and increased in those homozygous at the common allele rs11203366-GG, rs874881-CC.