COVID-19 and Interstitial Lung Disease

Background and Objectives: COVID-19 is an infection caused by the SARS-CoV-2 coronavirus that may develop several complications. Interstitial lung disease (ILD) is the major long-term complication of COVID-19 disease leading to progressive lung fibrosis and reduced respiratory function. The aim of this narrative review is to provide an updated overview of post-COVID-19 ILD by examining research publications and clinical guidelines selected from PubMed, Web of Science, and major respiratory medicine journals from 2020 to 2025. Methods: ILDs are diagnosed by medical history, physiological examination, pulmonary function tests, and chest X-ray or high-resolution computed tomography (HRCT) scan. Lung biopsy, especially cryobiopsy or video-assisted thoracoscopic (VATS) biopsy, can be performed to define histological patterns and confirm the diagnosis. Results: Post-COVID-19 ILD is a chronic condition characterized by long-term respiratory symptoms, radiological findings, and reduced lung function. Fibrotic injury is a consequence of the initial infection and could be influenced by persistent inflammation and dysregulated tissue repair. Risk factors include severe acute illness, advanced age, male sex, and smoking. Clinical course and prognosis of post-COVID-19 ILD is uncertain, as most patients experience gradual improvement or stability, whereas others develop progressive lung function decline. Treatment of post-COVID-19 ILD is not presently defined by guidelines but comprises corticosteroids, antifibrotics (including new drugs such as nerandomilast), supportive oxygen, pulmonary physiotherapy rehabilitation, smoking cessation, and vaccination. Conclusions: ILD represents a significant long-term complication of COVID-19 infection. Further investigations are required to better understand its pathophysiology and clinical management. As research progresses, more effective diagnostic and therapeutic strategies are expected to emerge.