Interstitial lung disease (ILD), ordiffuse parenchymal lung disease

(DPLD),[

[1] is a group of lung diseases affecting the interstitium (the tissue and spacearound the air sacs of the lungs).

[2] It concerns alveolar epithelium, pulmonary capillary endothelium,basement membrane, perivascular and perilymphatic tissues. It may occur

when an injury to the lungs triggers an abnormal healing response. Ordinarily,the body generates just the right amount of tissue to repair damage.

But in interstitial lung disease, the repair process goes awry and the tissuearound the air sacs (alveoli) becomes scarred and thickened.

This makes it more difficult for oxygen to pass into the bloodstream. Theterm ILD is used to distinguish these diseases from obstructive airways

diseases.

In children, several unique forms of ILD exist which are specific for the youngage groups. The acronym chILD is used for this group of diseases and is

derived from the English name, Children’s Interstitial Lung Diseases – chILD.[3]

Prolonged ILD may result in pulmonary fibrosis, but this isnot always the case.Idiopathic pulmonary fibrosis is interstitial lung disease forwhich no obvious cause can be identified (idiopathic), and isassociated with typical findings both radiographic (basal andpleural based fibrosis with honeycombing)and pathologic (temporally and spatially heterogeneousfibrosis, histopathologic honeycombing and fibroblastic foci).

In 2013 interstitial lung disease affected 595,000 peopleglobally This resulted in 471,000 deaths

1. Connective tissue and Autoimmune diseases1. Rheumatoid arthritis2. Systemic lupus erythematosus3. Systemic sclerosis4. Polymyositis5. Dermatomyositis

1. Infection1. Atypical pneumonia2. Pneumocystis pneumonia (PCP)3. Tuberculosis4. Chlamydia trachomatis5. Respiratory Syncytial Virus

1. Idiopathic1. Sarcoidosis2. Idiopathic pulmonary fibrosis3. Hamman-Rich syndrome4. Antisynthetase syndrome

MalignancyLymphangiticcarcinomatosis

Predominantly in children1. Diffuse developmental disorders2. Growth abnormalities deficient

alveolarisation3. Infant conditions of undefined cause4. ILD related to alveolar surfactant region

X-rays[Chest radiography is usually the first test to detect interstitial lung diseases, butthe chest radiograph can be normal in up to 10% of patients, especially early onthe disease process.[8][9]

Radiologic appearance alone however is not adequate and should be interpreted inthe clinical context, keeping in mind the temporal profile of the disease process.[8]

Interstitial lung diseases can be classified according to radiologic patterns

High resolution CT of the chest is the preferredmodality, and differs from routine CT of the chest.Conventional (regular) CT chest examines 7–10 mmslices obtained at 10 mm intervals; high resolutionCT examines 1-1.5 mm slices at 10 mm intervalsusing a high spatial frequency reconstructionalgorithm. The HRCT therefore providesapproximately 10 times more resolution than theconventional CT chest, allowing the HRCT to elicitdetails that cannot otherwise be visualized

Person with pneumocystis pneumonia canpresent with interstitial lung disease,as seen in the reticular markings

A chest X-ray demonstrating pulmonaryfibrosis due to amiodarone

Genetic testing[

For some types of chILD and few forms adultILD genetic causes have been identified. Thesemay be identified by blood tests. For a limitednumber of cases this is a definite advantage,as a precise molecular diagnosis can be done;frequently then there is no need for a lungbiopsy.

ILDs related to alveolar surfactantregion[Surfactant-Protein-B Deficiency(Mutations in SFTPB)Surfactant-Protein-C Deficiency (Mutations inSFTPC)ABCA3-Deficiency (Mutations in ABCA3)Brain Lung Thyroid Syndrome (Mutations inTTF1)Congenital Pulmonary Alveolar Proteinosis(Mutations in CSFR2A, CSFR2B)Diffuse developmental disorder[edit]Alveolar Capillary Dysplasia (Mutations inFoxF1)Idiopathic pulmonary fibrosis[edit]Mutations in telomerase reverse transcriptase(TERT)Mutations in telomerase RNA component(TERC)Mutations in the regulator of telomereelongation helicase 1 (RTEL1)Mutations in poly(A)-specific ribonuclease(PARN)

Treatment[ILD is not a single disease, but encompasses many differentpathological processes. Hence treatment is different for each disease.If a specific occupational exposure cause is found, the person shouldavoid that environment.If a drug cause is suspected, that drug should be discontinued.Many cases due to unknown or connective tissue-based causes aretreated with corticosteroids,[such as prednisolone. Some people respond to immunosuppressant treatment.Patients with a low level of oxygen in the blood may be givensupplemental oxygen.

Pulmonary rehabilitation appears to be usefulLung transplantation is an option if the ILD progressesdespite therapy in appropriately selected patients withno other contraindications.[On October 16, 2014, the Food and DrugAdministration approved a new drug for the treatmentof Idiopathic Pulmonary Fibrosis (IPF).This drug, Ofev (nintedanib), is marketed by BoehringerIngelheim Pharmaceuticals, Inc. This drug has beenshown to slow the decline of lung function although thedrug has not been shown to reduce mortality orimprove lung function. The estimated cost of the drugper year is approximately $94,000.