Swyer-James syndrome, also known as unilateral hyperlucent lung syndrome, refers to the manifestation of postinfectious obliterative bronchiolitis. Most patients do not develop symptoms while the remaining exhibit a productive cough, hemoptysis, exertional dyspnea, and decreased exercise tolerance. The diagnosis is based on a thorough history, physical exam, and imaging studies that characteristically reveal hyperlucency, hypovascularity, and a smaller lung.
Swyer-James syndrome is a rare pulmonary disease characterized by the presence of a unilateral hyperlucent lung . The disorder is the manifestation of postinfectious obliterative bronchiolitis of the lung or a part of the lung . Regarding the etiology, Swyer-James syndrome is thought to be acquired following infections that occurred during infancy or childhood . The most common pathogens include adenoviruses types 3, 7, and 21, while others such as paramyxovirus, Bordetella pertussis, Mycobacterium tuberculosis, Mycoplasma pneumoniae, Streptococcus pneumoniae, and influenza virus have also been implicated  .
The majority of patients are asymptomatic while some report a productive cough, hemoptysis, dyspnea on exertion, wheezing, and reduced tolerance to exercise   . Children may present with asthma-like features that do not respond to typical asthma therapy  . Asymptomatic individuals are likely to be diagnosed in adulthood .
Acute cases can result in complications such as respiratory distress and atelectasis while long-term consequences may include chronic and recurrent episodes of pulmonary infections such as bronchiolitis and pneumonitis   . Additionally, patients are at risk for developing sequelae such as bronchiectasis, which has prognostic implications  . Specifically, saccular bronchiectases are associated with more severe manifestations . Other complications of Swyer-James syndrome include lung abscesses and spontaneous pneumothorax .
On lung auscultation, the patient may exhibit diminished breath sounds on the involved side. Vital signs and the remainder of the exam may be unremarkable .
Patients with the above-described clinical presentation warrant a thorough workup. Diagnosis is achieved through a detailed history (which mainly confirms frequent childhood lung infections), physical exam, and the appropriate studies. Of importance, Swyer-James syndrome should be considered in individuals with an asthma-like presentation who lack a response to standard treatment .
Chest radiography will characteristically reveal unilateral hyperlucency of the lung or portion of the lung resulting from alveolar overdistension and decreased arterial flow   . Other features on this modality include hypovascularity, a mediastinal shift towards the affected lung, a small hilar shadow, and air trapping with expiration  .
Computed tomography (CT) scanning demonstrates greater sensitivity in depicting hyperlucency and the severity of the disease . This study also detects diminished vascularity, a smaller lung, and other pathologies such as bronchiectasis, atelectasis, scarring, etc  . Additionally, the bronchi of the affected lung reflect a pruned appearance while an air trapping, associated with an expiration, is also visible.
Magnetic resonance angiography (MRA) in these patients will display an underdeveloped pulmonary vasculature. Moreover, quantitative ventilation/perfusion lung scan reveals a decrease in both variables in the affected lung .
Finally, although it has limitations, pulmonary angiography demonstrates hypoplasia of the affected pulmonary artery .
Arslan N, Ilgan S, Ozkan M, et al. Utility of ventilation and perfusion scan in the diagnosis of young military recruits with an incidental finding of hyperlucent lung. Nucl Med Commun. 2001;22(5):525-530.