SWYER-JAMES SYNDROME (SYS)

Also known as the unilateral hyperlucent lung or Macleod's syndrome. It is an uncommon disease that is considered to be an acquired lesion that follows a number of lung insults, usually in infancy or childhood.

AETIOLOGY

The condition typically follows a lower respiratory tract infection in infancy or childhood. Thus it is a post infectious form of bronchiolitis obliterans following a number of lung insults;

Infections
Viral
Measles
Pertussis
Adenovirus
Bacterial
Tuberculosis
Mycoplasma
Others
Foreign body aspiration
Hydrocarbon pneumonia's
Radiation therapy
Toxic fumes
Organ transplantation

CLINICAL FEATURES

These tend to be variable and it is often an incidental finding on chest xray. Most patients are asymptomatic in adulthood. Others may complain of a cough, recurrent chest infections, shortness of breath, or hemoptysis.

PATHOGENESIS

This is not clear. Current theory favors a post infectious bronchiolitis obliterans. This follows on repeated infections in early childhood. The consequent bronchiolitis obliterans results in;

Distal airways trapping, airway distension and eventually changes characteristic of emphysema
Fibrosis of the lung with reduction in lung capacity and a compensatory reduction in pulmonary blood flow. Because the condition is usually acquired in childhood before the lungs have reached full development, the affected lung or lobe is usually small and hypo plastic
Bronchiectasis may or may not be present

FUNCTIONAL ABNORMALITY

Evidence of airway obstruction and increase in residual volume is present. There is diminished oxygen uptake in the affected lung. There is also decreased ventilation or blood flow in the affected lung.

DIAGNOSIS

The diagnosis is essentially a radiological one. The syndrome is primarily recognized by it's characteristic radiographic appearance of;

Lobar or unilateral hyperlucent lung
Small or normal lung volume on the affected side
Small hilar shadows
Sparse intrapulmonary vascular markings
Air trapping on expiration

Other diagnostic modalities such as bronchoscopy, bronchography, angiography and scintigraphy are also used to rule out other differentials such as;

unilateral agenesis or hypoplasia of a pulmonary artery
Massive pulmonary thromboembolism
Endobronchial tumor

More recently CT scans especially high resolution scans and spiral CT angiography have shown to be valuable modalities in confirming the diagnosis of SJS. It also allows for precise evaluation of vascular, bronchial and parenchymal structures.
CT scan also shows that although classically considered to affect one lung or lobe, the disease may be more heterogeneous in distribution and that contra lateral parenchymal lesions can be present.

TREATMENT AND PROGNOSIS

The prognosis is generally good. Most patients have an asymptotic course unless the opposite lung becomes diseased. The treatment is generally symptomatic. However, surgery should be considered if secondary infection or bronchiectasis become severe.

CONDITIONS THAT MAY PRESENT AS A UNILATERAL HYPERLUCENT LUNG


Technical difficulties
Pt rotation
uneven film development
Conditions that simulate a unilateral hyperlucent lung
pectoral muscle absence or wasting
absence of breast or soft tissue surgery
scoliosis
hypolucency of the contra lateral lung
Parenchymal Aetiologies
compensatory over inflation
emphysema
central obstruction of a bronchus
Vascular Aetiologies
pulmonary embolism
pulmonary artery stenosis or agenesis