Swyer-James syndrome: the lung that looks darker on a scan

Swyer-James syndrome is named after the doctors who described it in the middle of the twentieth century. A 2023 medical image review in the Southwest Journal of Pulmonary and Critical Care records that it was first described in 1949 in a six-year-old boy from the UK, by the paediatrician Paul Swyer and the radiologist George James, and that the pulmonologist William MacLeod later published a review of nine cases. Other names include Swyer-James-MacLeod syndrome and unilateral hyperlucent lung syndrome.

The condition is considered an acquired one. The review describes it as a post-infectious form of bronchiolitis obliterans, in which the small airways are scarred and narrowed after a severe infection early in life, while the lungs are still developing. Many different organisms have been associated, with respiratory syncytial virus the most implicated. A 2011 case report lists others reported in the literature, including measles virus, whooping cough bacteria, tuberculosis, mycoplasma, influenza A and adenoviruses.

Because the small airways are damaged, air gets trapped and the affected lung does not ventilate properly. The blood vessels supplying that area narrow in response, so the affected lung receives less blood than normal. On a scan this makes the lung look darker, or hyperlucent, compared with the healthy side.

The 2023 review states that most patients are asymptomatic and many cases are discovered incidentally, often as an unexpected finding on a chest X-ray or CT scan done for another reason. Others come to attention because of repeated chest infections, a long-standing cough, or breathlessness on exertion. The 2011 case report notes that people with little or no associated bronchiectasis may have minor symptoms or none and so may not be diagnosed until adulthood.

Symptoms that have been reported include a productive cough, shortness of breath on exertion and, sometimes, coughing up blood. These are non-specific, and all of them have much more common causes such as asthma, COPD and infection. See a GP if you have a cough lasting more than three weeks, repeated chest infections, or breathlessness that is new or getting worse. Coughing up blood, sudden severe breathlessness or chest pain needs urgent assessment through NHS 111, A&E or 999.

Diagnosis rests on imaging. The 2023 review explains that the most common pattern is a unilateral hyperlucent lung which may or may not be associated with hyperinflation and bronchiectasis. The 2011 case report describes the diagnosis as based on the radiological pattern: unilateral or lobar hyperlucency with air trapping on expiration, a pulmonary artery of reduced calibre and reduced blood flow.

The same report notes that a chest X-ray alone may underestimate or miss the syndrome and that the diagnosis is better established with high-resolution CT scanning taken during both breathing in and out, complemented where needed by a CT angiogram. A ventilation-perfusion lung scan can also be used, although the report cautions that false positives can occur in any condition that obstructs the small airways. The 2011 report describes an obstructive-restrictive pattern on lung function tests in its patient, which is the kind of finding a respiratory team may look for.

In the NHS the usual route is GP referral to a respiratory clinic, where a chest physician will review the imaging and decide whether further tests are needed. The 2011 report notes that other conditions can produce a similar appearance, such as bronchiolitis obliterans, asthma or congenital lobar emphysema, which is why specialist review of the images matters.

Most people do well, but there are things to be aware of. In the 2011 case report, an adult with undiagnosed Swyer-James syndrome was found to have pulmonary arterial hypertension and heart failure alongside a congenital heart abnormality, and the authors point out that it was not clear which factor contributed most to the clinical picture. This is a single case and should not be taken as typical.

The affected lung is also more prone to infection and to bronchiectasis, in which the airways are widened and prone to mucus build-up. The case reports mention that airway damage and hyperinflation can compress healthy lung tissue. Someone with recurring infections should discuss this with their respiratory team because prompt treatment can limit further damage.

The 2023 review states that treatment is usually conservative and preventative, focused on controlling pulmonary infections, and that inhaled corticosteroids may have a limited role. The 2011 report lists early control of lung infections and influenza and pneumococcal vaccination as the mainstay, and notes that resection of the affected lung has been successful in some cases. There are no specific large studies of outcomes.

In practice, this means keeping vaccinations up to date as advised, not smoking, and seeking early treatment for chest infections. Follow-up, where needed, is usually with a respiratory physician, with repeat lung function tests or imaging if symptoms change.

Private respiratory consultation or imaging can be used to speed assessment, particularly when an abnormal scan has been found and you want an expert opinion, but long-term care generally continues alongside your NHS GP and respiratory team.

For people with few symptoms the diagnosis is mostly one of understanding an unusual scan: the abnormality dates from childhood and does not usually progress. Being aware of when to seek help for a chest infection is the practical priority, and your respiratory team can advise on exercise.

No UK patient charity page or NHS patient leaflet specifically on the syndrome was found when this guide was written, so the sources used here are medical case reports. If you have been given this diagnosis, ask your respiratory team to explain what your scans show and whether any lung function monitoring is planned.