Idiopathic pulmonary fibrosis (IPF, a chronic lung disease marked by excessive buildup of extracellular matrix or ECM, substances that provide structural support to cells, in the lungs) is still not fully understood, especially the role of ornithine aminotransferase (OAT, an enzyme that helps convert ornithine into proline). The gene discussed is OAT; the disease is pulmonary fibrosis.