The Swyer James syndrome is also called Macleod syndrome/ Bret’s syndrome / Janus syndrome in honor of workers who initially described this rare entity.[
2,
3] They also demonstrated its association with Fallot’s tetrology. The condition arises as a result of some viral insult in infancy or childhood. The agents which are implicated are adenovirus, respiratory syncital virus, influenza virus, Mycoplasma pneumoniae,
Streptococcus pneumoniae and
Staphylococcus. In the initial eight years of life the lung growth occurs by progressive alveolarization and later on the growth occurs by expansion of preexisting bronchi.
The infective insult during infancy or childhood results in post infectious acute obliterative bronchiolitis (usually developing after six months to three years), which causes arrest of growth and alveolarization leading to hypoplasia of affected lung with reduced vascularity with paucity of bronchial subdivisions (cut off at 4 th to 5 th generation). Proteases released by phagocytes may be causative for elastolysis. Increase in CD8+ cells is also noted in broncho alveolar lavage of patients suffering from Swyer James syndrome. The disease usually affects one lung; however, both lungs and part of the lung may be involved. The affected lung or portion of the lung will not develop properly and will be smaller than its counterpart along with evidence of air trapping, resulting in unilateral hyperlucency. Finally, fibrous obliteration of airway lumen occurs.
The usual presentation of the patient is recurrent bouts of cough, fever, dyspnoea, which may be exertional. Some times the patients may present with history of hemoptysis, as in one of our cases. Weight loss may also be present. The syndrome may be complicated by spontaneous multi vessel coronary dissection.[
4] The Swyer James syndrome results in chronic lung illness with abnormal lung dynamics during inspiration and expiration (demonstrated as abnormal time attenuation curves during inspiration and expiration) with air trapping which increases on expiration with bronchial and bronchiolar abnormalities. Placental transmogrification of lung has been described recently in patients of Swyer James syndrome,[
5] structures resembling placental villi in lung parenchyma were described.
After the initial infective insult radiographic findings appear after months to years. Usual investigations performed are chest radiograph, high resolution computed tomography (both of these investigation should be done in inspiration and expiration), MRI, angiography, ventilation perfusion scanning.
Chest X-ray is the initial modality of investigation which demonstrates small hyperlucent affected lung/ region with compensatory hyperinflation of contra lateral lung. Evidence of air trapping may be noted in expiration which is a sine qua non for making diagnosis of Swyer James syndrome. Swing of mediastinal may be noted towards the normal lung on expiration. The hila on the affected side will be smaller. Evidence of bronchiectasis, scarring, and irregular pulmonary vasculature may be noted. Excursions of hemi diaphragm will also be markedly asymmetrical. Brochography may show dilated bronchi with sharply terminated segments. It is rarely used now a days.
HRCT is done with thin collimation in both phases of respiration to demonstrate air trapping. For proper demonstration of mosaic pattern prone position may be required. There will be evidence of diffuse decrease in attenuation of lung parenchyma on the affected side which will be smaller in size with reduction in the broncho vascular markings and smaller ipsilateral pulmonary artery. Paucity of bronchial subdivisions, proximal bronchiectasis and expiratory air trapping are best appreciated on HRCT.[
6]
MRI itself does not contribute to the final diagnosis; however, MR angiography demonstrates smaller pulmonary artery and its branches on the affected side. The narrowed attenuated arteries coursing through the radiolucent lung will produce “pruned tree appearance”.
Matched ventilation perfusion defects may be demonstrated by ventilation perfusion scanning due to abnormal development of pulmonary vasculature and lung parenchyma. Marked air trapping may also be noted in the washout phase.[
7] Scintigraphy may demonstrate findings of Swyer James syndrome in absence of significant radiological signs with demonstration of additional areas of involvement which will be normal on radiograph.
The important differential diagnosis of the Swyer James syndrome are congenital lobar emphysema, congenital hypoplasia of the lung, hypoplastic pulmonary artery, compensatory unilateral emphysema secondary to lobectomy, pulmonary embolic disease, pneumothorax, foreign body in air way.[
8]
