What is Swyer-James-MacLeod syndrome?
Swyer-James-MacLeod syndrome is a rare acquired lung condition in which one lung, one lobe or part of a lobe looks abnormally dark (hyperlucent) on a chest X-ray or CT scan. The darkness reflects two things: air is trapped in that part of the lung because the small airways are narrowed, and the blood vessels supplying it are smaller and fewer than normal.
The condition is a form of post-infectious bronchiolitis obliterans. A severe viral or bacterial chest infection in infancy or early childhood scars the smallest airways while the lung is still developing, so the affected lung grows less than the other side. It is named after the doctors who described it in the 1950s, and is often called Swyer-James syndrome or MacLeod syndrome.
Many people are diagnosed as adults, sometimes by chance, after a chest X-ray done for an unrelated reason. Once recognised, the condition is usually stable, and most people live normal lives with simple preventive care.
Symptoms of Swyer-James-MacLeod syndrome
Symptoms range from none at all to frequent chest infections. Common features include:
- No symptoms: a substantial proportion of patients are discovered only on imaging.
- Recurrent chest infections: repeated episodes of cough, fever and sputum, often affecting the same side.
- Chronic cough: sometimes productive when bronchiectasis has developed in the damaged lung.
- Breathlessness on exertion: usually mild, but more noticeable if both lungs are involved to some degree.
- Wheeze: this can lead to a mistaken diagnosis of asthma.
- Coughing up blood: uncommon, usually related to bronchiectasis.
On examination the breath sounds may be quieter over the affected side, and crackles may be heard if there is bronchiectasis.
Causes and risk factors
The underlying cause is a serious lower respiratory infection in childhood that injures the bronchioles. Infections linked to the condition include adenovirus, measles, respiratory syncytial virus, influenza, Mycoplasma pneumoniae, whooping cough (pertussis) and childhood tuberculosis. The inflammation leads to scarring and blockage of the small airways (obliterative bronchiolitis), and the lung tissue beyond them stops developing normally.
Because the damage happens years before diagnosis, many adults do not remember the original illness. The condition is not inherited and is not contagious. Better childhood vaccination against measles and pertussis has made new cases less common.
How Swyer-James-MacLeod syndrome is diagnosed
The diagnosis is mainly made on imaging, together with a history that fits. The key step is to exclude other causes of a dark lung, some of which need urgent treatment.
| Test | What it shows |
|---|---|
| Chest X-ray | A hyperlucent lung or lobe that is normal or small in size, with sparse vessel markings |
| CT scan with inspiratory and expiratory images | Air trapping in the affected area, small pulmonary vessels, and any bronchiectasis |
| CT pulmonary angiography | A small but present pulmonary artery, which helps distinguish the condition from a missing or blocked artery |
| Ventilation-perfusion scan | Matched reduction of air entry and blood flow on the affected side |
| Lung function tests | Usually a mild obstructive pattern, sometimes normal |
| Bronchoscopy | Used when needed to exclude a foreign body or tumour blocking a bronchus |
Conditions that can look similar include an inhaled foreign body, a tumour obstructing a main airway, pneumothorax, congenital absence or narrowing of a pulmonary artery, chronic pulmonary embolism, large bullae and chest wall differences such as absence of a chest muscle. Bronchoscopy is arranged when an airway blockage cannot be ruled out on CT.
Treatment
There is no treatment that reverses the airway scarring, and none is needed in many patients. Care focuses on preventing infections and treating complications early.
Preventive care
- Influenza and pneumococcal vaccination.
- Complete avoidance of smoking and second-hand smoke.
- Early antibiotic treatment of chest infections, guided by sputum culture where possible.
Treating bronchiectasis and wheeze
If bronchiectasis is present, daily airway clearance techniques taught by a physiotherapist help to clear mucus. Inhaled bronchodilators are used when there is airflow obstruction or wheeze, and inhaled corticosteroids are reserved for those with a clear asthma-like component.
Surgery
Surgical removal of the affected lobe or, rarely, the whole lung is considered for patients with frequent severe infections or bleeding that do not respond to medical treatment, and only after careful testing shows the rest of the lung is working well. These decisions are made together with a thoracic surgeon.
Outlook and follow-up
The outlook is generally good. The condition does not usually progress once the lung has finished growing, and most people work, exercise and travel normally. Periodic review with lung function testing is recommended, and a repeat scan is arranged if symptoms change. Keeping a copy of the CT report is useful, because a dark lung on a future X-ray can otherwise cause alarm and unnecessary tests.
Children found to have the condition are followed jointly with paediatric pulmonology, with attention to vaccinations, growth and prompt treatment of infections.
When to seek urgent care
Seek prompt medical attention for high fever with worsening cough and breathlessness, chest pain, coughing up more than a small streak of blood, sudden severe breathlessness, or blue lips. Sudden one-sided chest pain with breathlessness can indicate a collapsed lung and needs same-day assessment.
Frequently asked questions
Is Swyer-James-MacLeod syndrome dangerous?
In most people it is a stable condition that causes few or no symptoms. The main risk is recurrent chest infection in the affected lung, which can usually be reduced with vaccination, avoidance of smoking and early treatment of infections.
Can the damaged lung recover?
The scarring of the small airways is permanent, so the affected lung does not return to normal. However, it does not usually get worse in adult life, and the healthy lung compensates well.
Is it the same as asthma?
No. Both can cause wheeze, but Swyer-James-MacLeod syndrome is fixed damage to the small airways on one side after a childhood infection, while asthma is reversible airway inflammation that affects both lungs.
Will I need surgery?
Most patients never need surgery. It is considered only for frequent severe infections or bleeding that persist despite good medical care, after a full assessment with a thoracic surgeon.
Can I travel by air or exercise normally?
Most people can fly and exercise without difficulty. Patients with lower oxygen levels or significant breathlessness should discuss flying with their doctor beforehand.
Can it be passed on to my children?
No. It is not inherited and is not contagious. Keeping children up to date with vaccinations against measles, whooping cough and other infections lowers the risk of the kind of infection that causes it.
Related conditions and procedures
Consult Dr. Gogineni Ratnakara Rao
Apollo Hospitals, Financial District: Monday to Saturday, 8:30 AM to 5:00 PM. Anything in Lung Clinic, Chanda Nagar: Monday to Saturday (Thursday closed), 6:00 PM to 9:00 PM.