Interstitial Lung Disease

Interstitial lung diseases are also known as diffuse parenchymal lung diseases.

Heterogenous group of primary lung diseases characterised by progressive lung fibrosis that begins in the interstitium and culminates in destruction of alveoli, alveolar ducts, and bronchioles.

ILD are subclassified on some combination of clinical, radiographic, or pathological factors into:

Epidemiology and Risk Factors

  • Incidence: ~30/100,000
  • Prevalence: ~80/100,000
    Higher in males than females.

Pathophysiology

Aetiology

Clinical Features

  • Drug cough
  • Haemoptysis
  • Wheezing
    Uncommon.
  • Pleuritic chest pain
  • Extrapulmonary symptoms
    • Arthralgia
    • Fever
    • Photosensitivity
    • Connective tissue symptoms

Assessment

History

  • PMHx
    Key associations include:
    • Connective tissue disease
    • Inflammatory bowel disease
    • Malignancy
  • Smoking status
    Important for determining differential:
    • Current or former smokers:
      • Pulmonary Langerhans cell histiocytosis
      • Desquamative interstitial pneumonitis
      • Respiratory bronchiolitis-interstitial lung disease
      • IPF
    • Never or former smokers:
      • Sarcoidosis
      • Hypersensitivity pneumonitis

Exam

Investigations

Bedside:

  • Echocardiogram
    Right heart function.

Laboratory:

A rheumatological screen consists of:

  • Initial investigations:
    • FBE
    • UEC
    • ESR
    • CRP
    • LFT
    • ANA
    • Rheumatoid factor
    • Anti-CCP antibodies
    • Vitamin D
    • Urinealysis
  • Second-line investigations
    For patients with strong clinical suspicion:
    • Anti-synthetase antibodies
    • Creatine kinase
    • Aldolase
    • Sjögren’s antibodies
      • SS-A
      • SS-B
    • Scleroderma antibodies
      • Anti-topoisomerase (Scl-70)
      • Anti-PM-1 antibody
      • Anti-centromere
    • Anti-dsDNA antibodies
    • Myositis-associated antibodies
      • Jo-1
      • PL-7
      • PL-12
    • ANCA
    • Anti-melanoma differentiation-associated gene 5
    • Overlap antibodies
      PM-1.
  • Blood
    • Rheumatoid screen

Imaging:

  • CXR
  • High-resolution CT chest

Other:

  • Pulmonary function tests

  • Cardiopulmonary exercise testing

  • Lung biopsy

    • Highly invasive
    • Significant procedural risk
    • May be appropriate when:
      • No other clear diagnosis
      • Failure of empirical therapy
      • Potential treatments are:
        • Morbid
        • Mutually incompatible
    • Useful for determining:
      • Presence of idiopathic interstitial pneumonia, e.g.:
        • Cryptogenic organising pneumonia
        • Acute interstitial pneumonia
      • Absence of:
        • Sarcoidosis
        • Hypersensitivity pneumonitis
        • Pulmonary histiocytosis

Diagnostic Approach and DDx

Differential diagnoses of interstitial opacities include:

Infectious interstitial pneumonia is more common in the immunocompromised.

  • Infective pneumonias:
    • Fungal
    • Atypical bacterial
    • Viral

Management

  • Preventative
  • Immunosuppression

Specific therapy:

  • Pharmacological
    • Immunosuppression
      • Corticosteroids
        • Nintedanib
        • Pirfenidone
  • Procedural
    • Lung transplantation
  • Physical
    • Chest physiotherapy
    • Pulmonary hygiene

Supportive care:

  • B
    • Supplemental oxygen
      Targeting SpO2 >88%.

Disposition:

Preventative:

  • Avoid precipitants/irritants
  • Smoking cessation

Marginal and Ineffective Therapies

Anaesthetic Considerations

Complications

Prognosis

Varies depending on cause. Treatment-responsive variants include:

  • Acute eosinophilic pneumonia
  • Cellular interstitial pneumonia
  • Cryptogenic organising pneumonia
  • Lymphocytic interstitial pneumonitis
  • Pulmonary capillaritis
  • Granulomatous interstitial pneumonitis
  • Alveolar proteinosis

Key Studies

References

  1. Antoine MH, Mlika M. Interstitial Lung Disease. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 [cited 2023 Sep 30].