RETNLB and idiopathic pulmonary fibrosis: It has been reported that the concentration of RELM-β is high in the lung epithelial cells, fibroblasts, alveolar macrophages, and desquamated alveolar cells of patients with scleroderma-associated pulmonary hypertension and idiopathic pulmonary fibrosis, thus suggesting a profibrotic role in the lung [28].