ACPA IgA was associated with RA with ILD (11.8 ± 42.7 vs. 4.1 ± 6.7 U/ml, respectively, P = 0.0159), AD (9.2 ± 34.4 U/ml, P = 0.0468), emphysema (14.0 ± 29.7 U/ml, P = 0.0020), and CLD (11.0 ± 37.6 U/ml, P = 0.0015). The gene discussed is PRTN3; the disease is rheumatoid arthritis.