Connective tissue diseases (CTDs) are a heterogeneous group of conditions characterized by circulating autoantibodies and autoimmune-mediated organ damage. Common CTDs with lung manifestations are rheumatoid arthritis, scleroderma or systemic sclerosis, Sjögren syndrome, polymyositis/dermatomyositis, systemic lupus erythematosis, mixed connective tissue disease, and undifferentiated connective tissue disease. The most common histopathologic patterns of CTD-related interstitial lung disease are nonspecific interstitial pneumonia, usual interstitial pneumonia, organizing pneumonia, and lymphoid interstitial pneumonia. Drug treatment of CTDs can cause complications, including opportunistic infection.