What are the symptoms of Interstitial Lung Disease (ILD)?

Symptoms of Interstitial Lung Disease

The cardinal symptoms of ILD are progressive exertional dyspnea (shortness of breath) and chronic dry cough, which develop insidiously over months to years. 1, 2

Primary Respiratory Symptoms

Dyspnea (Shortness of Breath)

• Progressive exertional dyspnea is the hallmark symptom, present in the vast majority of ILD patients and typically worsening gradually over time 1, 2, 3
• Severity ranges from minimal dyspnea on exertion to severe respiratory distress at rest 1
• The dyspnea severity correlates with the extent of radiologic abnormalities on imaging 1
• Approximately 30% of patients with ILD report cough as a presenting symptom 2

Cough

• Chronic dry, nonproductive cough is characteristic and occurs in most patients 1, 4, 3
• The cough is typically persistent and may precede dyspnea 1
• In some ILD subtypes (particularly Sjögren's-associated ILD), sputum production may occur 1

Physical Examination Findings

Lung Auscultation

• Fine, dry "Velcro-type" inspiratory crackles are detected in more than 80% of patients with idiopathic pulmonary fibrosis and are most prominent at the lung bases 5, 4
• These bibasilar fine crackles occur predominantly during end-inspiration and are a sensitive indicator for ILD 5, 6
• The presence of fine crackles should prompt immediate further investigation with high-resolution CT 5

Associated Systemic Symptoms

Constitutional Symptoms

• Fatigue is commonly associated with ILD, though less specific than respiratory symptoms 1
• In idiopathic bronchiolitis obliterans organizing pneumonia (BOOP), a flu-like illness with fever, malaise, and weight loss may herald disease onset in 40% of patients 1
• Chest pain may occur in some ILD subtypes, particularly Sjögren's-associated ILD 1

Temporal Patterns and Progression

Chronic Progressive Course

• Symptoms typically develop over months to years in most ILD subtypes 1, 7, 3
• Progressive worsening of dyspnea during follow-up correlates with radiologic progression 1

Acute Presentations

• Acute interstitial pneumonia (Hamman-Rich syndrome) presents fulminantly over days to weeks with fever, cough, and severe shortness of breath in previously healthy individuals 1
• Acute exacerbations can occur in established ILD, presenting as acute respiratory distress requiring emergency evaluation 8

Critical Clinical Pitfalls

Symptom Assessment Limitations

• Cough and dyspnea are relatively nonspecific and may have alternative causes including cardiac disease, asthma, or postnasal drainage 1
• In one study, 90% of patients with rheumatoid arthritis-associated ILD confirmed on imaging did not have dyspnea or cough, demonstrating that symptom assessment alone has poor sensitivity 5
• History and physical examination alone have poor diagnostic accuracy (dry cough: 15% sensitive, 89% specific; dry crackles: 69% sensitive, 66% specific) 1

When to Suspect ILD

• Any patient presenting with unexplained progressive exertional dyspnea, chronic dry cough, and bilateral basal fine crackles on auscultation warrants immediate consideration of ILD 4, 6
• Patients over 60 years old with these symptoms require particularly high suspicion for idiopathic pulmonary fibrosis 4
• High-risk populations (connective tissue disease, occupational exposures, family history) require lower threshold for investigation even with mild symptoms 1

Diagnostic Approach Beyond Symptoms

Symptoms alone are insufficient for ILD diagnosis and must be supplemented with objective testing 1, 3:

• High-resolution CT chest is approximately 91% sensitive and 71% specific for diagnosing ILD subtypes 2
• Pulmonary function testing (spirometry, lung volumes, DLCO) provides essential diagnostic and prognostic information 1, 2
• A comprehensive evaluation including detailed environmental and occupational history is crucial, particularly for hypersensitivity pneumonitis 7