Previously, Badillo Soto and colleagues identified that the expression of PAD2 was exclusive in patients with RA; however, the sample used in their analysis was synovial biopsies from RA patients [44], and in the present study, serum samples from both RA and RA-ILD patients were analyzed, along with those in BAL samples of RA-ILD patients. The gene discussed is PADI2; the disease is rheumatoid arthritis.