Diffuse interstitial lung disease

Disease Description (Causes and Symptoms)

• Definition summary: Diffuse interstitial lung disease (ILD) is a group of non-neoplastic and noninfectious diseases that primarily affect the pulmonary interstitium (the alveolar walls and surrounding connective tissue, capillaries, etc.). Lesions often involve not only the interstitium but also the tissues within and around the alveoli.
• Main causes (representative)
  • Idiopathic interstitial pneumonias, including idiopathic pulmonary fibrosis (IPF)
  • Occupational and environmental exposure (pneumoconiosis, coal or silica exposure, etc.)
  • Hypersensitivity pneumonitis (exposure to organic antigens)
  • Drug-induced causes (anticancer drugs, antibiotics, antirheumatic drugs, etc.)
  • Connective tissue disease-associated ILD (rheumatoid arthritis, systemic sclerosis, etc.)
  • Sarcoidosis, post-infectious sequelae, etc.
• Pathophysiology: Inflammation → tissue damage → progression of fibrosis (in some cases) causes thickening of the pulmonary interstitium and capillaries, resulting in impaired gas exchange (reduced diffusion capacity) and reduced lung volume (restrictive respiratory impairment).
• Main symptoms
  • Gradive exertional dyspnea (dyspnea during exercise)
  • Dry cough (nonproductive cough)
  • Fatigue, weight loss, fever (in some cases)
  • Digital clubbing (particularly common in IPF)
  • During acute exacerbation, rapidly worsening dyspnea and hypoxemia over several days to several weeks

Treatment Methods and Precautions

• Diagnostic approach (essential before establishing a treatment plan)
  • High-resolution chest CT (HRCT), pulmonary function tests (particularly DLCO), arterial blood gas analysis, 6-minute walk test
  • If necessary, bronchoscopy and BAL (lavage), or surgical or percutaneous lung biopsy (generally decided after multidisciplinary discussion)
  • Multidisciplinary diagnosis (pulmonology, thoracic radiology, pathology, etc.) is recommended
• Drug treatment (varies according to disease subtype)
  • Antifibrotic agents: pirfenidone, nintedanib
    • Used mainly for idiopathic pulmonary fibrosis (IPF); may also be used for some progressive fibrotic diseases (to inhibit progression)
    • Side effects: gastrointestinal symptoms, elevated liver enzymes (liver function monitoring is required), photosensitivity (pirfenidone), etc.
  • Anti-inflammatory and immunosuppressive agents: for systemic inflammatory and immune-mediated ILD (e.g., NSIP, CTD-ILD, and some cases of hypersensitivity pneumonitis)
    • Corticosteroids (for acute exacerbation or inflammation-predominant types), followed by consideration of mycophenolate, azathioprine, cyclophosphamide, etc.
  • For sarcoidosis and similar conditions, steroids are the first-line treatment
• Non-drug and supportive treatment
  • Oxygen therapy (if necessary), pulmonary rehabilitation, prescribed regular exercise
  • Vaccination (influenza, pneumococcal disease, and COVID-19 are recommended)
  • Smoking cessation and avoidance of harmful environmental or occupational substances (antigens)
  • Nutritional management and monitoring of weight and symptoms
• Procedures/Surgery
  • For patients with end-stage or progressive disease, lung transplantation is the only curative treatment option
• During acute exacerbation
  • Hospitalization, oxygen, and supportive treatment; consider high-dose steroids (evidence is limited), and rule out and treat infection
• Complications and precautions
  • Complications: pulmonary hypertension, chronic respiratory failure, pulmonary infection, bronchiectasis, pneumothorax, biventricular heart failure (right heart failure)
  • Precautions: Antifibrotic agents only slow disease progression and are not curative. Monitoring for drug side effects (liver enzyme levels, gastrointestinal symptoms, skin reactions, etc.) is necessary. Seek medical attention immediately if symptoms worsen rapidly.

Outpatient Visit Checklist (Preparation, Records, and Example Questions)

• What to bring
  • List of current medications (including prescription drugs, OTC drugs, herbal medicines, and supplements)
  • Copies of previous test results (chest X-rays/CT, pulmonary function tests, arterial blood gas tests, etc.) or information for accessing electronic medical records
  • Occupational and exposure history (current/past occupations, exposure situations such as farms or factories, and exposure to pet birds or mold)
  • Symptom change records: dyspnea (when it began and its worsening pattern), cough, fever, weight changes, and changes in exercise capacity (6-minute walk distance or impact on daily activities)
  • Whether oxygen is required and whether a portable oxygen concentrator is used; oxygen saturation measured at home (if available, record the values and circumstances)
• Information to tell the nurse or doctor during the outpatient visit
  • Whether there has been a recent acute exacerbation (how many days or weeks ago it began worsening)
  • History of taking new medications or receiving vaccinations
  • Symptoms of infection (fever, sputum, chills, etc.)
• Example questions to check before testing (for the patient)
  • Has your dyspnea suddenly worsened recently? During which activities does it worsen?
  • Are you exposed to dust, organic materials, or animals through your occupation or hobbies?
  • Does your oxygen saturation change during usual exercise?

General Example Questions to Ask the Doctor

• "What do my test results (CT and pulmonary function tests) mean? How advanced is the disease?"
• "What are the effects and expected side effects of the medication I should start (e.g., pirfenidone or nintedanib)? How will monitoring be performed?"
• "What environments or activities should I avoid in daily life? What are your recommendations regarding my workplace (or hobbies)?"
• "How do you determine when a lung transplant is needed? What are the indications and procedures for transplantation?"

Examples of Disease-Specific Questions (1–2)

• Regarding antifibrotic agents (when idiopathic pulmonary fibrosis is suspected or diagnosed)
  • "Would you recommend an antifibrotic agent (pirfenidone or nintedanib) in my case? When should treatment be started, and what degree of clinical benefit (extent of progression inhibition) can be expected?"
• Regarding confirmation of the diagnosis (when imaging findings are unclear or the cause is unknown)
  • "Has my case been discussed by a multidisciplinary team? Can a definitive diagnosis be made without a lung biopsy (surgical or percutaneous), and if a biopsy is needed, what are its risks and benefits?"

(If necessary, printing the questions above and showing them directly to the doctor during the outpatient visit may help with the consultation.)

Note: This information is general guidance based on general medical knowledge. Decisions regarding individual diagnosis and treatment should be made in consultation with the attending physician. Seek emergency medical care immediately in the event of acute dyspnea or severe worsening of symptoms.