A discussion with Briana DiSilvio, MD, a specialist in pulmonary and critical care at Allegheny Health Network
Interstitial lung disease (ILD) is a group of diffuse lung disorders caused by damage to the surface area responsible for gas exchange – the pulmonary parenchyma – by ongoing inflammation. The continued inflammation often leads to thickening (fibrosis) of the tissue and irreversible scarring, reducing the body’s ability to deliver oxygen to the bloodstream.
“Interstitial lung diseases are probably more appropriately classified under the category diffuse parenchymal lung diseases as the inflammation and fibrosis tend to extend beyond the interstitial bed to involve the alveoli, alveolar ducts, and bronchioles,” explained Briana DiSilvio, MD, a specialist in pulmonary and critical care at Allegheny Health Network.
Diffuse parenchymal lung diseases can be broadly grouped into six categories: idiopathic (without a known etiology), autoimmune-related, environmental/occupational exposures, granulomatous lung disease, drug-induced. High resolution CT chest can offer a better characterization of the disease and aid in diagnosis in cases of a normal-appearing chest x-ray.
According to the Pulmonary Fibrosis Foundation, general symptoms include respiratory distress, dry cough, fatigue and weakness, chest discomfort, “clubbing” of the fingertips, loss of appetite and weight loss.
While surgical lung biopsies may be definitive in establishing a diagnosis, they are frequently not needed when classic radiologic patterns are present on the high-resolution CT. In large academic institutions with well-established ILD centers, a multidisciplinary approach involving pulmonologists, rheumatologists, radiologists, pathologists, and cardiothoracic surgeons can increase the accuracy of an ILD diagnosis while avoiding risk associated with invasive, and possibly unnecessary, procedures.
A progressive phenotype is more likely in idiopathic pulmonary fibrosis (IPF) and those diffuse parenchymal lung diseases associated with autoimmune diseases: rheumatoid arthritis- ILD, systemic sclerosis- ILD, polymyositis/dermatomyositis-ILD. Lung function often rapidly declines with these diseases and fibrosis increases over time.
Treatment typically uses glucocorticoids and immunosuppressive therapies like prednisone, mycophenolate mofetil and rituximab.
“Indications to use glucocorticoids and immunosuppressive agents depends on the primary disease, systemic activity, degree of active inflammation in the lungs, potential for reversibility, and overall ILD clinical course,” DiSilvio said.
Once diffuse parenchymal lung diseases enter a chronic phase of lung injury characterized by fibrosis, architectural distortion, traction bronchiectasis, and occasionally honeycombing, glucocorticoids and immunosuppressive therapies may be less beneficial. In these instances, patients may benefit from one of two FDA approved anti-fibrotic therapies: nintedanib and pirfenidone.
“The caveat to utilization of these medications is that they do not reverse the existing fibrosis but rather, only slow the progression of disease,” DiSilvio said. “Unfortunately, anti-fibrotics can have an intolerable side effect profile for many patients which often leads to cessation of therapy.