PADI2 and idiopathic pulmonary fibrosis: PADI2 mRNA levels were significantly lower in IPF and RA-ILD compared to controls (p = 0.023 and p = 0.001 respectively) and in RA-ILD compared with IPF (p = 0.018) (Fig. 1b and Table 2), however PADI2 levels were similar in all groups in ever smokers.