With regard to drug-induced ILD, HLA-A*31:01 and HLA-DRB1*15:02 are known to be associated with methotrexate-induced ILD in Japanese patients with rheumatoid arthritis (RA), which induce ILD as a complication [20, 21], and DRB1*15 and *16 were associated with a risk of ILD in Japanese RA patients regardless of methotrexate treatment [22]. This evidence concerns the gene HLA-A and rheumatoid arthritis.