Throw out your down pillows and join The Curbsiders for this lively discussion on interstitial lung disease. While the hundreds of interstitial lung disease types make this topic a bit overwhelming, breathe easy knowing that pulmonologist, Dr. Erin Narewski @erinnarewski (Temple), can boil things down to an easy to approach framework in less time than it takes to complete a few 6-minute walk tests. In this episode, we walk through the classification, relevant patient history, workup, and management of interstitial lung disease.
Written and Produced by: Paul Williams, MD, FACP; Nicole Kus, David Madnick, and Peter Wikoff
Infographic and Cover Art: Edison Jyang
Show Notes: Deborah Gorth
Hosts: Stuart Brigham MD; Matthew Watto MD, FACP; Paul Williams MD, FACP
Editor: Paul Williams MD, FACP (written materials); Clair Morgan of nodderly.com
Guest: Erin Narewski DO, FCCP
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The pulmonary interstitium comprises the basement membrane, peri-vascular, and perilymphatic fibrous connective tissue, which supports the lung and covers everything including airways and acinar clusters. Nearly all circulating blood passes through this tissue, so any systemic disease can impact the lung interstitium.
Although the family of interstitial lung disease refers to a large–some would say overwhelmingly large–family of diseases, these conditions can be simplified by grouping them into four most common causes: connective tissue related diseases, sarcoidosis, hypersensitivity, and idiopathic. Less common causes of ILD include occupational exposures, drug induced, smoking related, and familial ILD.
A comprehensive patient history is the key to unlocking an ILD diagnosis. Questions can be focused on each of the causes of ILD. For a potential connective tissue etiology, questions about changes in skin, hair, dry eyes, or dry mouth can indicate the underlying pathology. Presence of arthropathy or fatigue could indicate sarcoidosis. Hypersensitivity to antigens could be assessed with questions about wheezing or squeaking sounds in the chest, birds, down products, house age or a history of water damage at home or work. Possible occupational exposures can be assessed by asking the patient where they work or if they are required to wear ppe at work. Additionally, the Dyspnea 12 Questionnaire can be used to quantify symptomatology. Be careful when evaluating dyspnea; some patients adjust activity for lung function and may not feel short of breath.
The CHEST ILD questionnaire covers many medications linked to ILD, but additional history focused on medications can be useful. Some patients may not know that they received amiodarone while hospitalized for a cardiac condition, so it can be useful to ask about a history of cardiac surgery, arrest, or arrhythmia. If the patient has an extensive history of urinary tract infections, they may not remember the name of the medication they took, but nitrofurantoin could be a cause. A cancer history could indicate exposure to chemotherapy or radiation. Methotrexate has also been linked with ILD (Fragoulis et al 2019).
Is your patient an avid pigeon racer? While direct bird exposures are becoming less common, beware of luxurious down pillows and encourage patients to switch to fiber filled pillows if this could be contributing to their disease. Unfortunately, microwave popcorn has also been linked to ILD. The possible exposures contributing to ILD are vast, so the CHEST ILD questionnaire is a useful tool for evaluating for possible exposures.
Pulmonary crackles is the classic physical exam finding of ILD. However, many patients with ILD will have a normal lung exam. The crackles of ILD is a dry velcro sound as opposed to the “wet” rales associated with heart failure (Bohadana et al 2014). Digital clubbing is a common non-pulmonary physical exam finding of ILD (Sarkar et al 2012). Right heart strain and pulmonary artery hypertension are also late findings. The mouth, teeth, eyes, skin can also provide important information. Rashes, swollen joints, ulcers, chronic dry mouth leading to tooth or gum erosion can indicate connective tissue disease (Gupta et al 2019).
Initial tests for evaluating dyspnea potentially caused by ILD should include a CBC with a differential, basic metabolic panel, urine dipstick, and liver function tests. Additional tests to consider, depending on the clinical context, include an ESR, CRP, and a urinalysis if there is suspected vasculitis or kidney involvement (Wells and Hirani 2008). Consider scleroderma, myositis, or vasculitis workups if there is a suspicion of these conditions.
A plain chest x-ray has poor sensitivity for ILD, but remains an initial component of the workup for dyspnea. A high resolution CT scan of the chest without contrast is ideal for characterizing the lung parenchyma and diagnosing interstitial lung disease. This narrow beam approach results in high definition slices that are representative of lung tissue and can illuminate the character of diffuse disease.
Patterns on high resolution CT can provide an important clue for diagnosis, but it does not determine the diagnosis. Usual interstitial pneumonia (UIP) pattern–honeycombing, peripheral basal distribution, and absence of ground glass opacities–is the pattern most commonly associated with idiopathic pulmonary fibrosis, but you still need to do a full work up for other causes (Distefano et al 2020).
Normal lung function tests do not rule out ILD. Always order diffusion capacity along with spirometry and lung volumes. There can be mixed obstruction and restriction patterns, especially if there is also a smoking history.
The six minute walk test is easy and can be very useful for the initial work up of dyspnea to evaluate functional capacity. This test can be performed in the office using a 100-ft hallway, marked every 3 meters (ATS Guidelines). If there is dizziness while walking, consider pulmonary hypertension as part of the diagnosis. Or if they have chest pain, be concerned about cardiovascular disease.
Biopsy is not necessary for the diagnosis; this procedure can be dangerous, and it is rarely used.
Inhaled medications are helpful in a minority of patients who have airway involvement, but systemic medications are typically required. There is mixed evidence suggesting that proton pump inhibitors may have a role in treating interstitial lung disease, but more work is necessary to draw clear conclusions (Johannson et al 2017).
Antigen avoidance is the mainstay of treatment for hypersensitivity mediated ILD. Down pillows should be switched for fiber filled alternatives. If your patient is an avid duck hunter, maybe suggest transitioning to Nintendo Duck Hunt along with their nintedanib.
Nintedanib, pirfenidone act on cellular signaling cascade that lead to fibrosis inhibiting this process. These medications prevent acute exacerbations of ILD, slow fibrotic progression, and are now being used for early ILD (Maher and Strek 2019).
Steroid therapy in idiopathic pulmonary fibrosis is associated with an increase in mortality, so it is important to understand the etiology of ILD before prescribing this medication class (PANTHER-IPF 2012). Anti-inflammatory medications used for ILD include rituximab, mycophenolate mofetil, and azathioprine.
Pulmonary rehabilitation is a lot like boot camp for breathing and can improve short term morbidity, but these interventions need to be maintained. It is an opportunity to learn how to use oxygen. There is not a lot of data on the use of pulmonary rehabilitation for ILD, but pulmonary rehabilitation has been translated from other lung diseases and has been shown to provide benefit (Tonelli et al 2017).
Long term prognosis of progressive ILD is poor, and early involvement of palliative care can be helpful. When referring patients to a pulmonologist, be sure to refer to a center with lung transplant capabilities.
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Listeners will feel comfortable with the basic pathophysiology, diagnosis, and management of interstitial lung disease.
After listening to this episode listeners will…
Dr Narewski reports no relevant financial disclosures. The Curbsiders report no relevant financial disclosures.
Narewski E, Gorth DJ, Kus N, Madnick D, Wikoff P, Williams PN, Jyang E, Brigham SK, Watto MF. “#221 Interstitial Lung Disease with Erin Narewski DO”. The Curbsiders Internal Medicine Podcast. http://thecurbsiders.com/episode-list . June 22, 2020.
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Fragoulis GE et al. 2019. Methotrexate-associated pneumonitis and rheumatoid arthritis-interstitial lung disease: Current concepts for the diagnosis and treatment. Frontiers in Medicine 6:238.
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Sarkar M, Mahesh DM, Madabhavi I. Digital clubbing. Lung India 29(4): 354-362.
Tonelli R et al. 2017. Effectiveness of pulmonary rehabilitation in patients with interstitial lung disease of different etiology: A multicenter prospective study. BMC Pulmonary Medicine 17(1): 130.
Wells AU and Hirani N. 2008. Interstitial lung disease guideline. Thorax 63: v1-v58.
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