Swyer-James syndrome

Swyer-James syndrome (SJS), also known as Swyer-James-MacLeod syndrome and Bret syndrome, is a rare lung condition that manifests as unilateral hemithorax lucency as a result of postinfectious obliterative bronchiolitis.


The condition typically follows a viral respiratory infection such as adenoviruses or Mycoplasma pneumoniae infection in infancy or early childhood . Non-infectious cause includes ingestion of hydrocarbon. It has an estimated prevalence of 0.01% .

Radiographic features

Plain radiograph

It is generally characterized on radiographs by a unilateral small lung with hyperlucency and air trapping on expiration .


CT shows the affected lung as being hyperlucent with diminished vascularity. The disease can be unilateral or bilateral. The entire lung can be affected, however, there can also be lobar, segmental, and subsegmental involvement in a patchy distribution .  The size of the majority of the affected lobes is smaller, although occasionally they can be of normal size . There is usually no anteroposterior gradient attenuation . Bronchiectasis may be present, although this is not a universal finding .


MR angiography (MRA) may show a small pulmonary artery with diminished vascularity in the periphery .

Nuclear medicine

Quantitative ventilation/perfusion lung scan shows a photopenic area in the affected aspect.

Treatment and prognosis

Treatment is conservative and preventative, focused primarily on controlling pulmonary infections. Inhaled corticosteroids may have a limited role in treatment .

History and etymology

The condition was first described in Canada in the 1950s by:

  • Paul Robert Swyer: English pediatrician in Canada
  • William Mathieson MacLeod: English pulmonologist (1917-1977)
  • George C W James: Canadian radiologist

It has also been referred to as MacLeod syndrome, but this is not advised given the presence of a rare genetic malformation bearing a similar name: McLeod syndrome. It was also described by J Bret in France, hence reference to the same condition as Janus syndrome and Bret syndrome.

Differential diagnosis

Possible imaging differential considerations include:

One should also consider other causes of a unilateral hypertranslucent hemithorax.