Diffuse parenchymal lung disease, also referred to as interstitial lung disease, is a category of lung disorders that affect the interstitium in the lungs, according to WebMD. The interstitium is the network of tissues that extends throughout the lungs and supports the microscopic air sacs.
Diffuse parenchymal lung disease is characterized by inflammation of the interstitium due to progressive scarring, says Mayo Clinic. Causes of this disorder include medications such as sulfonamides and nitrofurantoin, as stated by MedlinePlus. Other causes include rheumatologic diseases, organic and occupational exposure such as working with asbestos or coal dust, radiation to the chest, and autoimmune diseases such as lupus and scleroderma.