The levels of rheumatoid factor, KL-6, and SP-D in ILD(+)RA were higher than those in CLD(–)RA (Table 1), although CLD(–) RA was matched for age group, sex, and the use of corticosteroids, csDMARDs, or b/tsDMARDs. Here, MUC1 is linked to rheumatoid arthritis.