Mucosal inflammation has long been considered the source of ACPA associated with seropositive RA, particularly IgA isotypes, and lymphoid follicles are common in both IPF and RA.23 28 It is thought that chronic infection or changes in the microbiome can promote protein citrullination via chronic inflammation and NETosis.32 Indeed, the predominant microbiota of both IPF and RA has been found to be the phyla Firmicutes. The gene discussed is CD79A; the disease is rheumatoid arthritis.