Fibrosis is recognized as pathogenic tissue remodeling, which is involved in a variety of diseases. This process is attributed to causing as much as 35% mortality worldwide [1]. Fibrotic changes contribute substantially to the pathogenesis of certain rheumatic diseases. While chronic inflammation in affected tissues is the hallmark of these conditions, fibrosis is a prominent histological feature in affected tissues of systemic sclerosis (SSc, scleroderma) [2] and IgG4-related disease (IgG4-RD) [3]. Fibrosis is seen in all other organs that are impacted in rheumatic disease, but is best described and investigated in the lung, where it is commonly referred to as interstitial lung disease (ILD). ILD is prevalent in 56% of patients with mixed connective tissue disease, 47% with scleroderma, 41% of patients with idiopathic inflammatory myositis, 17% of primary Sjogren's syndrome patients, 11% of rheumatoid arthritis (RA) patients, and in 4% of patients with systemic lupus erythematosus [4].

Therapy for fibrosis is extremely challenging and remains a severely unmet medical need, in spite of antifibrotic drugs approved for treating idiopathic pulmonary fibrosis (IPF) and systemic sclerosis associated ILD. One of the reasons that fibrosis having such mortality is that it is thought to be the final pathological process, which is often detected late and is not reversible. Recent studies in fibrosis and fibrotic changes in stroma of cancerous tissues have identified several potential therapeutic targets, which can be used for treating fibrosis in rheumatic diseases. This review summarizes pulmonary fibrosis with focus on approved antifibrotic therapies; and highlights interleukin (IL)-11 and fibroblast activation protein-α (FAP) as potential novel therapeutic targets for treating fibrosis.