Interstitial lung disease (ILD), also known as diffuse parenchymal lung disease (DPLD), refers to a group of lung diseases affecting the interstitium of the lung: alveolar epithelium, pulmonary capillary endothelium, basement membrane, perivascular and perilymphatic tissues. The term ILD is used to distinguish these diseases from obstructive airways diseases.
Most types of ILD involve fibrosis, but this is not essential; indeed fibrosis is often a later feature. The phrase "pulmonary fibrosis" is no longer considered a synonym, but the term is still used to denote ILD involving fibrosis. The term is commonly combined with idiopathic in "idiopathic pulmonary fibrosis", denoting fibrotic ILD that cannot be ascribed to a distinct primary cause.
ILD may be classified according to the cause. One method of classification is as follows
ILD is not a single disease, but encompasses many different pathological processes. Hence treatment is different for each disease.
If a specific occupational exposure cause is found, the person should avoid that environment. If a drug cause is suspected, that drug should be discontinued.
Many idiopathic and connective tissue-based causes of ILD are treated with corticosteroids, such as prednisolone. Some patients respond to immunosuppressant treatment. Patients with hypoxemia may be given supplemental oxygen.