The results of the subgroup analysis showed that ferritin (>336 ng/mL) (subgroup 1: OR = 4.737, p = 0.003; subgroup 2: OR = 6.407, p < 0.001) and CRP (>0.05 mg/L) (subgroup 1: OR = 4.771, p < 0.001; subgroup 2: OR = 3.114, p < 0.001) were associated risk factors for RP-ILD development in IIM patients, and ESR (>21 mm/h) was an associated risk factor particularly in subgroup 2 (OR = 1.521, p = 0.041). Here, CRP is linked to acquired idiopathic inflammatory myopathy.