11th January 2024

Classification

Classification of ILDs has been a subject of much debate. This is hardly surprising, given the sheer amount of disorders covered by the term. However, classifying ILD is clinically important, as management and prognosis often depend on its specific subtype.

The most widely used classification model is based on ILD aetiology. It can be established in approximately 35% of cases. Up to 65% fall under the ‘unknown aetiology’ category, which is then further subdivided into idiopathic interstitial pneumonias (IIPs) and ‘rare’/’ others’ (see below)

Adjusted from ‘Approach to the adult with interstitial lung disease: Clinical evaluation’. Talmadge E King, Jr, MD, ed. By Kevin R Flaherty, MD, MS. UpToDate.com [Internet]. https://www.uptodate.com/contents/approach-to-the-adult-with-interstitial-lung-disease-clinical-evaluation  

CTD-ILD: connective tissue disease-ILD; IIP: idiopathic interstitial pneumonia; IPF: idiopathic pulmonary fibrosis

Another way to classify ILDs has been proposed:

Native parenchymal disorders

• IPF
• Non-specific interstitial pneumonia (NSIP)
• Acute interstitial pneumonia (AIP)
• Cryptogenic organising pneumonia (COP)

Systemic disease-related ILD

• Connective tissue-related ILD (CTD-ILD), e.g. myositis, rheumatoid arthritis (RA), scleroderma, systemic lupus erythematosus (SLE)
• Vasculitides, e.g. granulomatosis with polyangiitis (GPA), Churg-Strauss syndrome (EGPA), anti-glomerular basement membrane (anti-GBM) disease

Exposure related CTD

• Drug-related
• Radiation related
• Hypersensitivity pneumonitis
• Post infective

Vascular disorders

• Diffuse pulmonary haemorrhage