(3) Fibrosis with the excessive repair: fibroblast and myofibroblast activation, secretion of growth factors, interleukins (IL)-17A, and matrix metalloproteinases (MMPs), fibroblast growth factor receptor (FGFR), etc. Fibrosis occurs with the excessive repair of lung tissue and blood vessels, excessive proliferation of fibroblasts, and massive accumulation of extracellular matrix (Fig. 2). The gene discussed is IL17A; the disease is fibrosis.