Interstitial Lung DiseaseEdit

Interstitial Lung Disease (ILD) refers to a broad group of disorders that affect the lung interstitium—the tissue and space around the air sacs in the lungs. These diseases commonly involve inflammation and/or scarring (fibrosis) of the alveolar walls, which can impair gas exchange and lead to progressive shortness of breath and cough. ILD encompasses idiopathic forms (where no cause is identified) as well as conditions linked to environmental exposures, autoimmune diseases, drugs, and other medical conditions. Because ILD describes a spectrum of diseases with overlapping features, a careful clinical, radiologic, and, when needed, pathologic assessment is essential for diagnosis and management. interstitial lung disease

In many forms of ILD, the underlying problem is the alteration of the lung’s architecture that disrupts the delicate balance between ventilation and perfusion. On imaging, these changes often appear as reticular (net-like) patterns, sometimes with honeycombing, especially in advanced fibrosis. The progression and severity of ILD vary widely by subtype and by individual factors such as age, smoking history, and exposure history. Treatments aim to slow disease progression, relieve symptoms, and preserve quality of life, rather than offering a cure for all conditions. fibrosis

Classification and etiologies

ILD is not a single disease but a collection of conditions with diverse causes and behaviors. Clinicians categorize ILD into several broad groups:

Idiopathic interstitial pneumonias, including idiopathic pulmonary fibrosis Idiopathic pulmonary fibrosis (IPF) and other entities such as nonspecific interstitial pneumonia nonspecific interstitial pneumonia. These forms have no identifiable external cause.
ILD associated with exposure to inhaled substances, including environmental or occupational agents such as asbestos asbestosis, inorganic dusts, metals, or organic dusts. Hypersensitivity pneumonitis develops when the immune system reacts to inhaled antigens (e.g., mold, bird proteins). hypersensitivity pneumonitis Exposure histories are central to identifying these conditions.
Connective tissue disease–associated ILD, in which autoimmune diseases such as systemic sclerosis, rheumatoid arthritis, or myositis involve the lungs and interstitium. systemic sclerosis and other autoimmune conditions frequently have a lung involvement pattern that resembles other forms of ILD.
Drug- and radiation-induced ILD, where certain medications or prior radiotherapy can damage lung tissue. drug-induced interstitial lung disease is an important consideration in patients with new respiratory symptoms during therapy.

The classification reflects not only etiology but also patterns seen on imaging and histology, which in turn influence management decisions. interstitial lung disease

Pathophysiology

ILD typically involves an abnormal wound-healing response to injury within the lung interstitium. Repetitive or ongoing injury may lead to persistent inflammation and progressive scarring (fibrosis). In some conditions, inflammation predominates early and may respond to anti-inflammatory medications; in fibrotic-dominant forms, antifibrotic therapies may be more relevant. The balance between inflammation and fibrosis, and the specific triggers involved, determine the rate of decline in lung function and the risk of complications such as respiratory failure. fibrosis

Clinical features

Most ILDs present with gradually worsening shortness of breath on exertion and a dry cough. Some patients also experience fatigue, chest discomfort, or weight loss. Physical examination may reveal crackles (rales) at the lung bases and, in advanced cases, signs of hypoxemia. The onset and pace of symptoms can vary widely between diseases and individuals. In occupational or environmental forms, clues often emerge from exposure histories.

Diagnosis

Diagnosing ILD requires integrating clinical history, physical examination, imaging, and often tissue sampling:

History and exam: Detailed review of symptoms, exposures, medication use, and any connective tissue disease symptoms.
Pulmonary function testing: Spirometry and diffusion capacity for carbon monoxide (DLCO) often show a restrictive pattern with reduced DLCO in many ILDs.
Imaging: High-resolution computed tomography (HRCT) is central to evaluation. Typical patterns on HRCT can suggest certain diagnoses (e.g., fibrotic reticulation with honeycombing in IPF; ground-glass opacities or a mosaic of airways in hypersensitivity pneumonitis). The interpretation of HRCT often guides the need for further testing. high-resolution computed tomography
Laboratory tests: Autoimmune serologies may help identify CTD-ILD; exposure-related testing may identify environmental etiologies.
Bronchoscopy and bronchoalveolar lavage (BAL): Can aid in excluding infection and may provide cellular patterns that support certain diagnoses.
Lung biopsy: In selected cases, a surgical lung biopsy (often via video-assisted thoracoscopic surgery) provides histopathologic guidance when noninvasive tests are inconclusive. lung biopsy

Because many ILDs share similar clinical and radiographic features, multidisciplinary discussion involving pulmonologists, radiologists, and pathologists improves diagnostic precision. multidisciplinary discussion

Management

Management is tailored to the specific ILD subtype, disease severity, comorbidities, and patient preferences. Key principles include:

Remove or minimize exposure when a trigger is identified (e.g., discontinue exposure to causative environmental or occupational agents). occupational exposure
Immunosuppression or immunomodulation: In inflammatory-dominant ILDs or certain CTD-ILDs, medications such as corticosteroids or steroid-sparing agents may be used. They are chosen based on diagnosis and likelihood of inflammation-driven disease.
Antifibrotic therapy: For some fibrotic ILDs, especially idiopathic pulmonary fibrosis Idiopathic pulmonary fibrosis, drugs that slow fibrosis progression have become standard care. Pirfenidone pirfenidone and nintedanib nintedanib are examples that have shown benefit in slowing decline in lung function in IPF and are being studied in other fibrotic ILDs.
Supportive care: Oxygen therapy for hypoxemia, pulmonary rehabilitation to improve exercise capacity, and vaccination to prevent respiratory infections are important components of care. pulmonary rehabilitation
Symptom management and palliative care: Addressing dyspnea, cough, fatigue, and quality of life is essential.
Transplant consideration: In advanced disease with poor prognosis or refractory symptoms, referral for lung transplantation lung transplantation can be an option in appropriately selected patients.
Special considerations by subtype: Hypersensitivity pneumonitis management focuses on antigen avoidance, while CTD-ILD management concentrates on controlling the underlying autoimmune disease.

Clinical management often requires ongoing monitoring of lung function, imaging, and symptom trajectory to adjust therapy as the disease evolves. monitoring lung disease

Prognosis and epidemiology

Prognosis in ILD varies widely by subtype and individual factors. IPF, for example, is typically progressive and carries a substantial risk of mortality within a few years of diagnosis, while other ILDs may stabilize or improve with appropriate treatment and exposure avoidance. Early recognition and management generally correlate with better outcomes, underscoring the importance of timely diagnosis and multidisciplinary care. Epidemiology reflects a mix of idiopathic forms and disease associated with exposures or systemic diseases, with variations by age, sex, smoking status, and geographic region. IPF sarcoidosis

Prevention and public health considerations

Prevention focuses on reducing exposure to known inhalational agents (e.g., asbestos, organic dusts), occupational safety measures, smoking cessation, and early treatment of autoimmune conditions that can involve the lungs. Public health and regulatory policies influence the prevalence of exposure-related ILD, though the path from exposure to disease is individual and multifactorial. asbestosis