Theme -> lung dysrepair = scar, destruction of tissue, fibrogenesis

  • interstitial lung disease
  • there’s ~300 interstitial lung disorders
  • but, you can focus on the subgroup of interstitial diseases
  • *”the interstitial lung diseases are diverse group of lung infiltrations that disrupt alveolar structures; and have in common clinical, radiographic and physiologic consequences”
    • there’s no single variable that will define; you need a couple of variables to define

Hierarchy: ILD -> IIP -> IPF

ILD – interstitial lung disease

  • inflammation, fibroblasts, collagen deposition
  • Syndrome of ILD
    • 1) SOB, 2) b/l infiltrates, 3) physiologic abnormalities, and 4) fibrosis/inflammation on histology
    • usually chronic in presentation
    • think though about whether you really need a biopsy or not -> i.e. if they have a connective tissue disorder and they have the SOB, infiltrates and physiologic abnormality you probably skip the biopsy and assign the pulmonary disorder to the connective tissue disorder.
  • catch-all term -> collagen vascular d/o, granulomatosis disease (i.e. sarcoid), inhalation causes, drug-induced causes, idiopathic interstitial pneumonias, lymphangioleiomytosis

Idiopathic interstitial pneumonias (IIPs)

  • the prototype/most common type of idiopathic interstitial pneumonias (IIP) is IPF
  • of note, the histologic patterns allow the separation of these conditions more than the radiologic patterns


  • allows us to come to diagnosis better
  • histo and CT chest

General treatment of ILDs

  • oxygen
  • rehab
  • eval for cancer
  • immunosuppression/antifibrotics -> pirfenidone (King N Engl J Med 2014) or nintedanib (Richeldi N Engl J Med 2014) may slow the progression of disease
  • lung transplant

IPF became the general term/overdiagnosis from the 1970s approach

  • then, they determined that there were differences in responses to treatment and difference in patterns
  • then, they realized that there were different diseases
  • HISTOLOGY + HRCT + physiology = IPF


UIP (usual interstitial pneumonitis—aka truly the IPF) was common pattern that was related to heterogeneity -> areas of normal-ness and areas of not-normal

  • poor 5y survival
  • IPF is the most common of the ILD and the IIPs
    • usually in older pts
    • now, there’s 2 FDA-approved treatments
    • mechanism -> dysfunctional epithelium -> chronic state of injury
      • mutations in surfactant and mucin proteins
      • component of chronic aspiration?
    • IPF is a peripheral changes with normal adjacent areas -> heterogeneity is characteristic along with accumulation with fibroblastic foci and honeycombing
  • Classic HRCT findings
    • 1) basilar and peripheral predominance 
    • 2) honeycombing – irreversible scar tissue
    • 3) traction bronchiectasis
    • 4) no other abnormalities (i.e. no masses/nodes)

*could be linked to connective tissue disorders

*could have UIP pattern on histo but not the other aspects -> the clinical presentation

*example -> a cohort of polymyositis or dermatomyositis could have 1) NSIP, 2) organizing PNA, or 3) usual interstitial pneumonitis; similarly, a cohort of rheumatoid arthritis patients could have 1) nonspecific interstitial pneumonia, 2) respiratory bronchiolitis, 3) normal histology

  • conclusion is that you can have variable histology 

NSIP (nonspecific interstitial pneumonia) was bland pattern of diffuse inflammation

  • 5y survival is better with NSIP than UIP

AIP (acute interstitial pneumonitis) significant thickness

DIP (desquamative interstitial pneumonitis) black cells (thought to be dead/desquamative)

BOOP – has accumulation of cells in the airwyas and inflammation of the small airways

  • more responsive to steroids than the other above pathologies
    • So, you need a biopsy to distinguish
    • Since, in the 1970s all you had for tx was steroids, we stopped doing biopsies and just empirically treated

*Connective tissue disorders are commonly linked to development of ILD


Bronchiolitis obliterans related to transplantation

  • rejection

Cystic changes vs. fibrotic changes

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