Pirfenidone, a new oral antifibrotic agent, has been approved for the treatment of idiopathic pulmonary fibrosis (IPF). Randomized controlled trials of pirfenidone in patients with IPF suggested that it could ameliorate pulmonary function decline and improve the progression-free survival. Its utility in connective tissue disease (CTD) related ILD has been implicated, but no evidence has yet demonstrated its efficacy. Therefore, the investigators conduct this study to evaluate the possible therapeutic effects of pirfenidone on RPILD associated with CADM.