Cryptogenic organising pneumonia

Cryptogenic organising pneumonia (COP) is a disease of unknown aetiology. A wide variety of infectious as well as noninfectious causes may result in a similar histologic pattern.

Organising pneumonia (OP) is a histologic pattern of alveolar inflammation with varied aetiology (including pulmonary infection). The idiopathic form of OP is called cryptogenic organising pneumonia (COP) and it belongs to idiopathic interstitial pneumonias (IIP's).

COP was previously termed bronchiolitis obliterans organising pneumonia (BOOP), not to be confused with bronchiolitis obliterans per se 8.

The presentation is commonest in the 55-60 age group. 

Patients present with a short history (i.e. less than ~2 months) of breathlessness, non-productive cough, weight loss, malaise and fever. There is no association with smoking.

In addition to the alveolar inflammatory changes found with regular pneumonia, there is also the involvement of the bronchioles.

Histologically, it is characterised by mild chronic patchy interstitial inflammation without fibrosis and the presence of buds of granulation tissue made of mononuclear cells, foamy macrophages, and fibrous tissue (Masson bodies) in the distal airspaces which may cause secondary bronchiolar occlusion due to extension of the inflammatory process. Hence, the reason for being previously termed bronchiolitis obliterans organising pneumonia (BOOP).

Plain radiograph
  • consolidation
    • unilateral or bilateral patchy areas (commonest finding 3): often migratory
    • can affect all lung zones
    • usually peripheral, subpleural, peribronchovascular 2
  • nodules
    • foci of granulation tissue up to 1 cm
    • may mimic neoplasm if >5 cm in size
    • may be numerous in immunocompromised patients
CT

The most common HRCT features include 6:

  • patchy consolidation with a predominantly subpleural and/or peribronchial distribution
  • small, ill-defined peribronchial or peribronchiolar nodules
  • large nodules or masses
  • bronchial wall thickening or dilatation in the abnormal lung regions
  • a perilobular pattern with ill-defined linear opacities that are thicker than the thickened interlobular septa and have an arcade or polygonal appearance
  • ground glass opacity or crazy paving

The reverse halo sign (atoll sign) is considered to be highly specific, although only seen in ~20% of patients with COP 5.

It was first described by Davison and colleagues in 1983.

Corticosteroids have been widely used and most patients recover completely 3-4.

On radiograph consider:

On CT consider:

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Article Information

rID: 7109
System: Chest
Section: Pathology
Synonyms or Alternate Spellings:
  • Bronchiolitis obliterans organizing pneumonia (BOOP)
  • Cryptogenic Organizing Pneumonia (COP)
  • Bronchiolitis obliterans organising pneumonia (BOOP)
  • COP
  • BOOP
  • Bronchiolitis obliterans with organizing pneumonia (BOOP)
  • Cryptogenic organising pneumonia (COP)
  • Cryptogenic organizing pneumonia
  • Cryptogenic organising pneumonia
  • Bronchiolitis obliterans with organising pneumonia (BOOP)
  • Cryptogenic Organising Pneumonia (COP)
  • Bronchiolitis obliterans organising pneumonia (BOOP)

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Cases and Figures

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    Case 1: with atoll sign
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    Case 3: with atoll sign
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