Obliterative bronchiolitis

Obliterative bronchiolitis (also termed bronchiolitis obliterans / constrictive bronchiolitis) is type of bronchiolitis and refers to bronchiolar inflammation / sub mucosal peribronchial fibrosis associated with luminal occlusion / stenosis and should not be confused with bronchiolitis obliterans organising pneumonia (BOOP). 

Pathology

The condition is characterised by concentric luminal narrowing of the membranous and respiratory bronchioles as a result of submucosal and peribronchiolar inflammation and fibrosis without any intraluminal granulation tissue or polyps / polyposis. There is an absence of diffuse parenchymal inflammation.

It can result from number of causes

• idiopathic / cryptogenic
• post infectious
  • post viral 
  • post atypical infection (e.g. Mycoplasma pneumonia)
• noxious fume inhalation
• neuroendocrine hyperplasia (carcinoid tumourets) ⁴
• post transplant patients 
  • heart / lung transplants ³
  • haematopoetic stem cell transplants ⁷ 

Mnemonic : CRITTS

Associations

Recognised associations include

• inflammatory bowel disease
• rheumatoid arthritis
• medications : e.g. penicillamine

Radiographic features

Plain film / Chest radiograph

Can be normal or non specific. some associated features incude

• hyperinflation
• attenuation of vascular markings
• occassionally : reticular or reticulo-nodular markings

HRCT

There are often sharply defined, areas of decreased lung attenuation associated with vessels of decreased caliber. These changes represent a combination of air trapping and oligaemia. This combination can give a mosaic attenuation pattern.

Other features include

• bronchial dilatation
• bronchiolar wall thickening ⁶
• ground glass opacities ⁶

Etymology

It was first described by A.C.Reynaud in 1835 ^8-9