Swyer-James Syndrome (SJS)

Axial Computed Tomography of the chest reveals a small hyperlucent left lung with atresic vascular structures and evidence of air trapping characteristic of the Swyer-James syndrome.

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

• Paul Robert Swyer : English paediatrician 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 to be used du to the presence of a rare genetic syndrome resulting in slowly progressive degeneration of a variety of tissues including blood, brain, peripheral nerves, muscle and heart - bearing a very closely similar name: McLeod syndrome.

Swyer-James syndrome (SJS) is a manifestation of postinfectious obliterative bronchiolitis. In SJS, the involved lung or portion of the lung does not grow normally and is slightly smaller than the opposite lung. The characteristic radiographic appearance is that of pulmonary hyperlucency, caused by overdistention of the alveoli in conjunction with diminished arterial flow.

Plain X-ray Chest revealed the left lung is smaller and more lucent compared to the right. In addition, the pulmonary vessels on the left are smaller and don't extend as far peripherally as those on the right.

For patients with Swyer-James syndrome, chest computed tomography (CT) scanning with thin collimation sections on inspiration and expiration is the preferred examination. The appearance of the lungs on forced expiration is important in the assessment of SJS with CT scanning; therefore, the patient's co-operation is essential. The patient should be placed in the prone position to help identify the typical mosaic pattern of the syndrome.

In Swyer-James syndrome, the bronchi have a pruned appearance. A mosaic pattern of air trapping in acini is seen, along with air trapping during expiration. The appearance is similar to that of hypoplastic lung syndrome. In addition, the appearance of Swyer-James syndrome is the same as that of bronchiolitis obliterans, but bronchiolitis obliterans is more frequently a diffuse process.

CT aids in the differential diagnosis between SJS, bronchial obstruction and congenital vascular anomalies like unilateral pulmonary artery agenesis or scimitar syndrome, showing preserved anatomy of tracheobronchial tree and pulmonary arteries. Currently available post-processing tools improve MDCT diagnostic performances; in particular the combination of multiplanar reformatted images with maximum intensity projection (MIP) is most effective in vascular imaging while minimum intensity projection (minIP) reconstructions help to disclose differences in lung attenuation and depiction of bronchial structures.

a.Chest X-rays showing reduced left lung volume and herniation of hyperinflated right lung (arrow).

b, c. Axial CT scan and minIP coronal reconstruction reveal hyperlucency of left lung and airways patency.

d. Contrast enhanced MIP coronal reconstruction reveal left pulmonary arteries have strikingly decreased caliber.