Interstitial lung disease

of usual interstitial pneumonia (UIP). UIP is the most common pattern of idiopathic interstitial pneumonia (a type of interstitial lung disease) and usually represents idiopathic pulmonary fibrosis. H&E stain. Autopsy specimen. ILD may be classified as to whether its cause is not known (idiopathic) or known (secondary). Idiopathic Idiopathic interstitial pneumonia is the term given to ILDs with an unknown cause. They represent the majority of cases of interstitial lung diseases (up to two-thirds of cases). They were subclassified by the American Thoracic Society in 2002 into 7 subgroups: • Smoking-related interstitial fibrosis (SRIF) is an example of a type of interstitial lung disease known to be caused by smoking. Infection • Coronavirus disease 2019 (COVID-19) • Atypical pneumonia • Pneumocystis pneumonia (PCP) • Tuberculosis • Chlamydia trachomatis • Respiratory syncytial virus Malignancy • Lymphangitic carcinomatosis Childhood interstitial lung disease and ILD predominately in children • Diffuse developmental disorders • Growth abnormalities and deficient alveolarisation • Infant conditions of undefined cause • ILD related to alveolar surfactant region == Diagnosis ==

can present with interstitial lung disease, as seen in the reticular markings on this AP chest x-ray. due to amiodarone Diagnosis of ILD involves assessing the signs and symptoms as well as a detailed history investigating occupational exposures. ILD usually presents with dyspnea, worsening exercise tolerance and 30-50% of those with ILD have a chronic cough. On examination, velcro crackles, in which the crackles compare to the sound of velcro being unfastened, are common in ILD. A lung biopsy may be required if the clinical history and imaging are not clearly suggestive of a specific diagnosis or malignancy cannot otherwise be ruled out. Surgical lung biopsy or via a video-assisted thoracoscopic surgery (VATS) biopsy is associated with a mortality rate up to 1-2%. A bronchoscopic transbronchial cryobiopsy, in which a camera is introduced into the airways followed by rapid freezing of an area of lung tissue prior to biopsy is associated with a lower complication rate and a much lower mortality rate compared to VATS or surgical biopsy with near comparable diagnostic accuracy. There are four types of histopathologic patterns seen in ILD: usual interstitial pneumonia, non-specific interstitial pneumonia, organizing pneumonia, and diffuse alveolar damage. Although there is large diversity in interstitial lung disease, most follow a restrictive pattern. Restrictive defects are defined by decreased TLC (total lung capacity), RV (residual volume), FVC (forced vital capacity) and FEV1 (forced expiratory volume in one second). As both FVC and FEV1 are reduced, the FVC to FEV1 ratio remains normal or is increased. High-resolution CT of the chest is the preferred modality and differs from routine CT of the chest. Conventional (regular) CT chest examines 7–10 mm slices obtained at 10 mm intervals; high resolution CT examines 1–1.5 mm slices at 10 mm intervals using a high-spatial-frequency reconstruction algorithm. The HRCT therefore provides approximately 10 times more resolution than the conventional CT chest, allowing the HRCT to elicit details that cannot otherwise be visualized. Radiologic appearance alone, however, is not adequate and should be interpreted in the clinical context, keeping in mind the temporal profile of the disease process. Interstitial lung diseases can be classified according to radiologic patterns. Pattern of opacities Consolidation • Acute: • Alveolar hemorrhage syndromes • Acute eosinophilic pneumonia • Acute interstitial pneumonia • Cryptogenic organizing pneumonia • Chronic: • Chronic eosinophilic pneumonia • Cryptogenic organizing pneumonia • Lymphoproliferative disorders • Pulmonary alveolar proteinosis • Sarcoidosis Linear or reticular opacities • Acute: • Pulmonary edema • Chronic: • Idiopathic pulmonary fibrosis • Connective tissue-associated interstitial lung diseases • Asbestosis • Sarcoidosis • Hypersensitivity pneumonitis • Drug-induced lung disease Small nodules • Acute: • Hypersensitivity pneumonitis • Chronic: • Hypersensitivity pneumonitis • Sarcoidosis • Silicosis • Coal workers pneumoconiosis • Respiratory bronchiolitis • Alveolar microlithiasis Cystic airspaces • Chronic: • Pulmonary Langerhans cell histiocytosis • Pulmonary lymphangioleiomyomatosis • Honeycomb lung caused by idiopathic pulmonary fibrosis (IPF) or other diseases Ground glass opacities • Acute: • Alveolar hemorrhage syndromes • Pulmonary edema • Hypersensitivity pneumonitis • Acute inhalational exposures • Drug-induced lung diseases • Acute interstitial pneumonia • Chronic: • Nonspecific interstitial pneumonia • Respiratory bronchiolitis-associated interstitial lung disease • Desquamative interstitial pneumonia • Drug-induced lung diseases • Pulmonary alveolar proteinosis Thickened alveolar septa • Acute: • Pulmonary edema • Chronic: • Lymphangitic carcinomatosis • Pulmonary alveolar proteinosis • Sarcoidosis • Pulmonary veno-occlusive disease Distribution Upper lung predominance • Pulmonary Langerhans cell histiocytosis • Silicosis • Coal workers pneumoconiosis • Carmustine-related pulmonary fibrosis • Respiratory broncholitis associated with interstitial lung disease Lower lung predominance • Idiopathic pulmonary fibrosis • Pulmonary fibrosis associated with connective tissue diseases (ILD-CTD) • Asbestosis • Chronic aspiration Central predominance (perihilar) • Sarcoidosis • Berylliosis Peripheral predominance • Idiopathic pulmonary fibrosis • Chronic eosinophilic pneumonia • Cryptogenic organizing pneumonia Associated findings Pleural effusion or thickening • Pulmonary edema • Connective tissue diseases • Asbestosis • Lymphangitic carcinomatosis • Lymphoma • Lymphangioleiomyomatosis • Drug-induced lung diseases Lymphadenopathy • Sarcoidosis • Silicosis • Berylliosis • Lymphangitic carcinomatosis • Lymphoma • Lymphocytic interstitial pneumonia Genetic testing For some types of paediatric ILDs and few forms adult ILDs, genetic causes have been identified. These may be identified by blood tests. For a limited number of cases, this is a definite advantage, as a precise molecular diagnosis can be done; frequently then there is no need for a lung biopsy. Testing is available for ILDs related to alveolar surfactant region • Surfactant protein B deficiency (mutations in SFTPB) • Surfactant protein C deficiency (mutations in SFTPC) • ABCA3 deficiency (mutations in ABCA3) • Brain–lung–thyroid syndrome (Mutations in TTF1) • Congenital pulmonary alveolar proteinosis (mutations in CSFR2A and/or CSFR2B) Diffuse developmental disorder • Alveolar capillary dysplasia (mutations in FoxF1) Idiopathic pulmonary fibrosis • Mutations in telomerase reverse transcriptase (TERT) • Mutations in telomerase RNA component (TERC) • Mutations in the regulator of telomere elongation helicase 1 (RTEL1) • Mutations in poly(A)-specific ribonuclease (PARN) == Treatment ==

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. Oxygen therapy Oxygen therapy at home is recommended in those with significantly low oxygen levels. Oxygen therapy in ILD is associated with improvements in quality of life but reductions in mortality are uncertain. Pulmonary rehabilitation Pulmonary rehabilitation appears to be useful with the benefits being sustainable longer term with improvements in exercise capacity (as measured by a six-minute walking test), dyspnea, and quality of life. Medications The antifibrotics pirfenidone and nintedanib have been shown to slow the decline in lung function (as measured by forced vital capacity [FVC]) in those with ILD compared to placebo. Nintedanib was also associated with a slower FVC decline and increased mean survival in people with ILD. Supportive care Those with ILD should stop smoking cigarettes if they smoke. Vaccinations against pneumococcus, COVID-19, RSV and influenza are indicated in all those with ILD. Short acting opiates are known to improve breathlessness symptoms in those with end stage lung disease. The opiate agonist-antagonist nalbuphine and morphine are also known to improve coughing in those with ILD and other end stage lung diseases. ==Prognosis==

The median survival in idiopathic pulmonary fibrosis is 3–3.5 years. However, prognosis varies widely depending on the specific type and cause of ILD; some inflammatory forms may stabilize or improve with treatment. ILD is associated with a 3-fold increased risk of lung cancer. Life expectancy after lung transplant is 5.2 years in those with idiopathic interstitial pneumonias (including idiopathic pulmonary fibrosis) and 6.7 years in those with other types of ILD. == References ==