Susannah Hollywood - 1400 word in-depth article - created June 2023
What is Interstitial Lung Disease?
Overview
Interstitial (in-tur-STISH-ul) lung disease is an umbrella term for over 100 different lung conditions,1 involving inflammation and scar tissue formation in the interstitial lung tissue (pulmonary fibrosis). The interstitial tissue of the lung is the network of tissue that supports the air sacs (alveoli), where the exchange of oxygen for carbon dioxide takes place. When scar tissue forms within this network, the tissue thickens, hardens and becomes less elastic (Asthma and Lung UK). This reduces the lung’s ability to expand sufficiently to allow normal intake of air. These structural changes to the alveoli also inhibit optimal gas exchange in the lungs (National Heart, Lung, and Blood institute). The result is shallow or laboured breathing and decreased oxygen entering the body.
The most common Interstitial lung disease conditions found in Europe are Idiopathic pulmonary fibrosis (IPF) and Sarcoidosis.2
Causes of interstitial lung disease
The cause of Interstitial lung disease is not known3 but according to the American Lung Association, the following factors are thought to increase risk of its development:
● genetics
● certain medications
● certain medical treatments such as chemotherapy and radiotherapy
● smoking
● exposure to asbestos
● exposure to other hazardous occupational materials such as silica, dust arising from wood, metal, coal, sand, farming or livestock4
● co-existence of other conditions such as:
○ Hypersensitivity pneumonitis, a condition caused by exposure to allergens such as household mould, bird droppings or bird feathers
○ Autoimmune diseases such as rheumatoid arthritis (a connective tissue disease)5
There is ongoing research into whether Gastro-oesophageal reflux disease (GERD) is a risk factor for some Interstitial lung disease conditions. Findings from studies carried out so far have not been conclusive and further research is required.1
In some cases, such as Idiopathic pulmonary fibrosis and Sarcoidosis, the causes and risk factors are unknown.3, 6
Signs and symptoms of Interstitial lung disease
Signs and symptoms of Interstitial lung disease are often non-specific and common to many respiratory conditions. These include:
● Breathlessness
● Cough
● Fatigue
● Insomnia
● Reflux
● Psychological problems such as anxiety and depression7,8
Management and treatment for Interstitial lung disease
The damage caused to lungs by Interstitial lung disease is often permanent and cannot be repaired. The condition is also usually progressive (it gets worse over time). Treatment therefore focuses on slowing disease progression to prevent further lung damage occurring, as well as reducing symptoms.
Medication used to slow the disease progression varies depending on the type of condition involved and its severity. Differential diagnosis with a specific condition is therefore fundamental to the success of treatment.1 Conditions involving lung inflammation may respond to treatment with anti-inflammatory medication such as steroids,1 whilst conditions involving fibrotic changes may instead be treated with anti-fibrotic therapy.3
Treatment focusing on providing relief from symptoms and improving quality of life may include oxygen therapy1 and pulmonary rehabilitation.8 Pulmonary rehabilitation programmes provide education and advice - for example techniques to improve efficiency of breathing and reduce feelings of breathlessness, advice on self-management of respiratory conditions, as well as structured exercise programmes to improve endurance.
In extreme cases, lung transplantation may be recommended.1
Treatment may involve a multidisciplinary team of health care providers (specialists from different fields who work together) and may take place in a specialist Interstitial lung disease clinic.4
Diagnosis of Interstitial lung disease
Specific and accurate diagnosis of Interstitial lung disease is important in order for the correct management approach to be taken1 and the following elements may be included in an assessment:
● History taking including relevant occupational information
● Physical examination including listening to breath sounds
● Lung function tests (to check how well the lungs are working)
● Blood tests
● Chest X-rays
● CT (computerised tomography) scan
● Bronchoscopy - insertion of a thin tube with a camera attached via the nose or mouth to reach the lung, in order to provide visual information on the lung tissue and/or remove a small piece of tissue for further examination
● surgical lung biopsy - removal of small piece of tissue for further examination, carried out as surgery1
The findings of all test and assessment results will be combined to help the clinician to differentiate between different conditions which are similar in nature.1 However, differences between conditions can be subtle and diagnostic criteria vary.
As a result, accurate diagnosis can be challenging, even for experienced clinicians, and initial misdiagnoses are not uncommon. Due to this, and the time required to undergo all tests and diagnostic procedures and wait for interpretation of results, there is frequently significant delay in reaching the true diagnosis.9
As Interstitial lung disease is progressive, it is important for it to be diagnosed as early as possible and treatment started to prevent deterioration. Research shows that a delay in referral to a specialist unit for treatment is linked to worse prognosis, and it is recommended that suspected cases are referred without delay.4
However, early diagnosis is hampered by a frequent lack of specific symptoms during the early stages of the disease. Indeed, a significant proportion of patients are not diagnosed with Interstitial lung disease until receiving acute care for an exacerbation (a sudden worsening of symptoms).10
Risk factors
How and why Interstitial lung disease develops is not fully understood.3 Genetics may contribute, as may the presence of other health conditions and the use of certain medications or treatments.
In addition, the exposure to certain environmental and lifestyle factors may increase risk of development of these conditions, and these include:
● Smoking
● Exposure to hazardous substances such as asbestos, wood/metal dust or other occupational materials
● Inhalation of allergens such as bird droppings, bird feathers and mould
Complications
Interstitial lung disease can range significantly in severity, from mild to life-threatening. Complications include pulmonary hypertension (high pressure in the blood vessels running from the heart to the lung) and potentially life-threatening conditions of heart failure and respiratory failure. (American Lung Association)
Interstitial lung disease patients can experience exacerbations11 (acute episodes of worsening of symptoms) and these can result in admission to hospital. Depending on the severity, admission to the Intensive Care Unit (ICU) may be required for treatments such as ventilation.10
While the mechanism for these flare-ups is not fully understood, it is thought that infection, air pollution and micro-aspiration may contribute, (when small volumes of liquid are aspirated or drawn into the lungs). However, many exacerbations are considered to be idiopathic (having no known cause).10
FAQs
How can I prevent Interstitial lung disease?
The causes and mechanisms involved in Interstitial lung disease are complex and not fully understood. They may include genetics, co-existence of other conditions and exposure to certain medications/treatments. It is thought that certain environmental and lifestyle factors - such as smoking and exposure to hazardous substances and allergens - may also increase the risk of development of Interstitial lung disease and should be avoided.
How common is Interstitial lung disease?
The lung conditions classed as Interstitial lung disease are rare, but there is insufficient data available to specify exactly how many people worldwide have them. There are a number of barriers to the recording of true data in this area, including a lack of consensus in classification and diagnostic criteria,2 and a shortage of data in this area from developing countries.12
Global figures from studies show a range of 6 - 98 people per 100,00013 having Interstitial lung disease, with figures from The International Respiratory Coalition showing an average of 53.7 cases per 100,000 in Europe.
However, figures vary considerably from country to country and a recent review of worldwide study data found differences between individual European countries ranging from 6.27 - 71 people per 100,000.2 It is not yet possible to confirm whether this variation between populations is due to true differences in demographics and environmental exposures, or due to differences in diagnosis, classification and recording of data.2 Further research is needed for clarification.
When should I see a doctor?
The symptoms of Interstitial lung disease are non-specific and common to many respiratory conditions. They often do not appear until the disease has already significantly progressed. As a result, diagnosis is challenging and often missed or delayed.9
The damage caused by Interstitial lung disease can be irreversible, and so early diagnosis is critical. It is therefore important to consult a healthcare provider if you experience any ongoing respiratory problems, including shortness of breath or persistent cough.
Summary
Interstitial lung disease is an umbrella term for a number of different chronic lung conditions which involve inflammation and fibrosis of the lungs. The structural changes that take place with these diseases result in changes to respiratory function and a reduction in the amount of oxygen taken into the body. The main symptoms experienced are shortness of breath and cough. The damage caused by these conditions can be permanent, but treatment may be able to slow progression, as well as to reduce symptoms and improve quality of life.
Interstitial lung diseases can be challenging to diagnose as symptoms may not be experienced until significant damage to lung tissue has already occurred. If you experience ongoing respiratory symptoms, consult a Healthcare Practitioner for further advice.
References
Vancouver Style
1. Meyer KC. Diagnosis and management of interstitial lung disease. Transl Respir Med [Internet]. 2014 Feb 13 [cited 2023 May 30];2(1):4. Available from: https://doi.org/10.1186/2213-0802-2-4
2. Kaul B, Cottin V, Collard HR, Valenzuela C. Variability in global prevalence of interstitial lung disease. Front Med (Lausanne) [Internet]. 2021 Nov 4 [cited 2023 May 30];8:751181. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8599270/
3. Torrisi SE, Pavone M, Vancheri A, Vancheri C. When to start and when to stop antifibrotic therapies. European Respiratory Review [Internet]. 2017 Sep 30 [cited 2023 May 30];26(145). Available from: https://err.ersjournals.com/content/26/145/170053
4. Cottin V. Interstitial lung disease. European Respiratory Review [Internet]. 2013 Mar 1 [cited 2023 May 30];22(127):26–32. Available from: https://err.ersjournals.com/content/22/127/26
5. Vij R, Strek ME. Diagnosis and treatment of connective tissue disease-associated interstitial lung disease. Chest [Internet]. 2013 Mar [cited 2023 May 30];143(3):814–24. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3590889/
6. Zhang H, Costabel U, Dai H. The role of diverse immune cells in sarcoidosis. Front Immunol [Internet]. 2021 Nov 19 [cited 2023 May 30];12:788502. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8640342/
7. Carvajalino S, Reigada C, Johnson MJ, Dzingina M, Bajwah S. Symptom prevalence of patients with fibrotic interstitial lung disease: a systematic literature review. BMC Pulm Med [Internet]. 2018 Dec [cited 2023 Jun 1];18(1):78. Available from: https://bmcpulmmed.biomedcentral.com/articles/10.1186/s12890-018-0651-3
8. Nakazawa A, Cox NS, Holland AE. Current best practice in rehabilitation in interstitial lung disease. Ther Adv Respir Dis [Internet]. 2017 Feb [cited 2023 Jun 1];11(2):115–28. Available from: http://journals.sagepub.com/doi/10.1177/1753465816676048
9. Cosgrove GP, Bianchi P, Danese S, Lederer DJ. Barriers to timely diagnosis of interstitial lung disease in the real world: the INTENSITY survey. BMC Pulmonary Medicine [Internet]. 2018 [cited 2023 May 30];18. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5773175/
10. Charokopos A, Moua T, Ryu JH, Smischney NJ. Acute exacerbation of interstitial lung disease in the intensive care unit. World J Crit Care Med [Internet]. 2022 Jan 9 [cited 2023 Jun 1];11(1):22–32. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8788209/
11. Leuschner G, Behr J. Acute exacerbation in interstitial lung disease. Frontiers in Medicine [Internet]. 2017 [cited 2023 Jun 1];4. Available from: https://www.frontiersin.org/articles/10.3389/fmed.2017.00176
12. Dhooria S, Sehgal IS, Agarwal R, Muthu V, Prasad KT, Kathirvel S, et al. Incidence, prevalence, and national burden of interstitial lung diseases in India: Estimates from two studies of 3089 subjects. PLoS One [Internet]. 2022 Jul 21 [cited 2023 May 31];17(7):e0271665. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9302724/
13. Taveira-DaSilva AM, Moss J. Clinical features, epidemiology, and therapy of lymphangioleiomyomatosis. CLEP [Internet]. 2015 Apr [cited 2023 May 31];249. Available from: http://www.dovepress.com/clinical-features-epidemiology-and-therapy-of-lymphangioleiomyomatosis-peer-reviewed-article-CLEP
14. Badillo R, Francis D. Diagnosis and treatment of gastroesophageal reflux disease. World J Gastrointest Pharmacol Ther [Internet]. 2014 Aug 6 [cited 2023 May 31];5(3):105–12. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4133436/
15. Maher TM, Strek ME. Antifibrotic therapy for idiopathic pulmonary fibrosis: time to treat. Respir Res [Internet]. 2019 [cited 2023 May 31];20:205. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6731623/
16. Lee JS, Collard HR, Raghu G, Sweet MP, Hays SR, Campos GM, et al. Does chronic microaspiration cause idiopathic pulmonary fibrosis? Am J Med [Internet]. 2010 Apr [cited 2023 May 31];123(4):304–11. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2851633/
17. Nikkho SM, Richter MJ, Shen E, Abman SH, Antoniou K, Chung J, et al. Clinical significance of pulmonary hypertension in interstitial lung disease: A consensus statement from the Pulmonary Vascular Research Institute’s innovative drug development initiative—Group 3 pulmonary hypertension. Pulm Circ [Internet]. 2022 Jul 1 [cited 2023 May 30];12(3):e12127. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9395696/
18. Cottin V, Hirani NA, Hotchkin DL, Nambiar AM, Ogura T, Otaola M, et al. Presentation, diagnosis and clinical course of the spectrum of progressive-fibrosing interstitial lung diseases. Eur Respir Rev [Internet]. 2018 Dec 21 [cited 2023 May 30];27(150):180076. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9489068/