Swyer-James-MacLeod syndrome (SJMS), also known as Swyer-James syndrome or hyperlucent lung syndrome, is an uncommon syndrome of unilateral functional hypoplasia of the pulmonary vasculature and emphysema, with or without associated bronchiectasis. The condition was first described simultaneously in the 1950s by a respiratory physician William Mathieson Macleod in England (1954) and by a physician Paul Robert Swyer and a radiologist George James in Canada (1953).
This rare lung condition is characterized by radiographic hyperlucent appearance of a single pulmonary lobe or the entire lung. It is considered to arise as a postinfectious complication of bronchiolitis obliterans in childhood.
Initially, Swyer-James-MacLeod syndrome was believed to be congenital in origin, secondary to inborn hypoplasia of the pulmonary artery. Although its definitive cause remains uncertain, it is now widely accepted to be a rare complication of childhood respiratory infections, most commonly bronchiolitis obliterans or pneumonitis. The causative agents implicated in the recurrent pulmonary infections include viruses (measles, respiratory syncytial virus, influenza A, Paramyxovirus morbillivirus, adenovirus types 3, 7 and 21) and bacteria (Bordetella pertussis, Mycobacterium tuberculosis, Mycoplasma pneumoniae).
Due to its rarity, little is known about the overall incidence of Swyer-James-MacLeod syndrome. Despite its first characterization in 1953, the available literature comprises mostly individual case reports and series. One study reported a prevalence of 0.01% in a series of 17,450 reviewed chest radiographs. Many cases remain undiagnosed or are treated as other conditions, such as asthma or bronchiectasis due to the diagnostic challenges. SJMS has been reported to occur in approximately 4% of patients with bronchiolitis obliterans. For unclear reasons in most patients, there is a preferential involvement of the left lung.
Swyer-James-MacLeod syndrome, also known as Swyer-James syndrome and Bret syndrome, is considered as a result of postinfectious obliterative bronchiolitis.
Bronchiolitis obliterans (or obliterative bronchiolitis) describes a clinical syndrome of small airway obstruction that is irreversible to bronchodilators. It is triggered by the injury of the bronchiolar epithelium and possibly the adjacent alveoli. This damage, which occurs during early childhood, hinders the normal development of the alveolar ducts.
The injury may be caused by a range of factors with respiratory infections playing a major role in Swyer-James-MacLeod syndrome. While complete recovery is possible, the repair process may lead to a surplus proliferation of granulation tissue, resulting in narrowing or complete obliteration of the small airways. Unilateral recurrent small airway obstruction involving terminal bronchi and bronchioles occurring early in life triggers an inflammatory response, which leads to the development of submucosal fibrosis. The resulting luminal irregularity further contributes to airway occlusion, becoming more permanent. This, in turn, causes alveolar air trapping, eventually resulting in emphysema, which is defined as permanent overdistention of the airspaces distal to the terminal bronchioles. Alveolar wall destruction leads to the loss of elastic recoil, causing airway collapse during exhalation and air trapping. Therefore, the typical appearance of unilateral hyperlucency can be found on radiographs.
The other, and perhaps more important, factor responsible for the radiographic hyperlucency of a single hemithorax is the reduction of the pulmonary blood flow. Fibrosis of the interalveolar septae leads to obstruction of the pulmonary capillary bed and also reduces blood flow to the major pulmonary artery branches. Moreover, hyperinflation of alveoli, as seen in emphysema, creates additional mechanical resistance to blood flow through the capillary beds. Since this process occurs early in life, arterial development is thwarted, resulting in the hypoplastic pulmonary vasculature.
Additionally, reduced ventilation of the diseased lung or segment also leads to compensatory vasoconstriction of the pulmonary vessels, leading to a functional restriction of the arterial flow, which contributes further to the radiographic hyperlucency. Functional hypoplasia of the bronchial vasculature may impair the growth of the affected lung, leading to a lung that is either small or normal in size. In some patients with Swyer-James-MacLeod syndrome, bronchiectasis may develop proximal to bronchiolitis obliterans and is likely a sequela of chronic infections.
Histopathological studies in patients with Swyer-James-MacLeod syndrome (SJMS) are scarce and based solely on the limited number of cases that required surgical intervention.
Histological studies of the diseased lung frequently demonstrate emphysema with dilated bronchioles and cystic dilatation of the alveoli, as well as constrictive bronchiolitis. Emphysema is usually patchy and may be of the panacinar type. Other potential changes include mucus plugging and chronic inflammation. Some studies reported hypoplasia of the pulmonary artery and the alveoli. However, there is some speculation that the hypoplasia of the pulmonary vasculature seen on imaging is primarily functional (reflecting reduced blood flow) as some pathological studies resected lungs in SJMS demonstrated a pulmonary artery of normal caliber or only slightly smaller than expected.
Many patients with Swyer-James-MacLeod syndrome are asymptomatic, whereas some suffer from recurrent pulmonary infections. Some patients are diagnosed in childhood, others incidentally during adulthood when undergoing investigations for a different reason (such as the symptoms of asthma or recurrent chest infections). This rare condition poses a diagnostic challenge as its presentation may be non-specific and mimic other respiratory conditions, including Congenital lobar emphysema(CLE), pneumothorax, or localized pulmonary interstitial emphysema, bronchopulmonary sequestration, Poland syndrome, etc.
When symptomatic, patients most often present with recurrent pulmonary infections or exertional dyspnea. Other symptoms include wheezes, dyspnea on exertion, reduced exercise tolerance, cough (often productive) with or without hemoptysis, and pleuritic chest pain. Most patients, however, are asymptomatic.
The main physical findings include reduced chest expansion, hyper-resonant on percussion, and decreased breath sounds on the affected side. In cases where the mediastinum is shifted to the affected side, the apex beat may also be displaced.
Swyer-James-MacLeod syndrome has a broad spectrum of clinical presentations. Because of its rarity, there are no recommended guidelines regarding diagnostic work-up.
The diagnostic criteria for this syndrome require one of the following three:
The management of Swyer-James-MacLeod syndrome is patient-centered and delivered using the interprofessional team approach.
Conservative management is the mainstay of treatment.
Prevention and prompt treatment of recurrent respiratory infections: Primary prevention such as pneumococcal and influenza vaccination is necessary. Mucolytics may be helpful in patients with bronchiectasis. Chest physiotherapy employing techniques like percussion and postural drainage are important to ensure efficient sputum clearance. Corticosteroids and inhaled bronchodilators are also used. In cases of respiratory failure, long-term oxygen therapy may be indicated. Patients should also be referred for pulmonary rehabilitation to maximize respiratory function.
Surgical intervention is reserved for (1). patients with recurrent pulmonary infections, (2). patients who fail to respond or (3). patients whose symptoms are not adequately controlled with optimal medical management. Surgical options include pneumonectomy or lung volume reduction surgery, such as lobectomy or segmentectomy. This has previously been achieved without significant morbidity but with a dramatic improvement of symptoms and respiratory function. Lung volume reduction surgery has been particularly successful in patients with significant hyperinflation (secondary to emphysema), as it may exert a favorable effect on the mechanics of the airways, diaphragm and chest wall.
An interesting new approach has also been proposed in one study, where patients underwent occlusion of the main bronchus while the lung was left in place. It was postulated that this procedure is less traumatic than pneumonectomy as the operation is carried out through a small thoracotomy without the need to enter the pleural space. The disconnected lung acts as a biological prosthesis preventing the herniation and hyperexpansion of the remaining healthy lung and mediastinal displacement. Any possible infection was successfully avoided with the help of bronchial washings and the use of high-dose wide-spectrum antibiotics before and after the surgery. Within two years after surgery, fibroatelectasis of the severed lung is expected to develop, and the inflammation should resolve. Moreover, it is believed that this strategy can be successfully utilized specifically in Swyer-James-MacLeod syndrome because there is no blood flow to the affected lung; if a healthy lung was occluded, right to left shunt and hypoxemia would develop.
The unilateral hyperlucency of the lung can be due to reduced pulmonary blood flow or hyperinflation of terminal airways. Therefore, conditions with one or both of those features can mimic Swyer-James-MacLeod syndrome.
The differential diagnosis includes both congenital and acquired lung disorders:
SJMS patients generally have a normal life expectancy. While Swyer-James-MacLeod syndrome has a spectrum of manifestations, its clinical course is largely determined by the presence or absence of bronchiectasis. Patients without or only with cylindrical bronchiectasis often suffer from mild respiratory symptoms and tend to improve spontaneously. Those with saccular bronchiectasis, on the other hand, suffer from recurrent episodes of pneumonia and are the ones at the highest risk of requiring surgical intervention.
The major complication of SJMS is the development of bronchiectasis accompanied by chronic productive cough. Bronchiectasis predisposes patients to further respiratory infections. The presence of bullae also increases the risk of developing a spontaneous pneumothorax and limit the patients' activities in diving or air travel. There have also been reports of SJMS complicated by a lung abscess.
As the lung function gradually declines with time, patients may develop type I respiratory failure and require long-term oxygen therapy. This situation has a significant impact on their independence and quality of life.
Finally, patients requiring surgical procedures are at risk of surgical complications such as infection of surgical sites, nerve damage, pneumothorax, emphysema, and surgical emphysema. The risks are, however, extremely small, and in all cases reported to date, patients experienced no morbidity as a result of the surgery, and their lung function improved significantly.
Finally, patients should be referred for chest physiotherapy and educated on the importance of adherence to regular chest clearing exercises.
It is essential for clinicians at outpatient, inpatient, or emergency settings to keep Swyer-James-Macleod syndrome in the differentials for adult or pediatric patients presenting with shortness of breath. A hyperlucent lung field on radiography is alarming, early and correct diagnosis avoids unnecessary invasive procedures (such as chest drain insertion for misdiagnosed pneumothorax) and reduces further deterioration of lung function. The most common and concerning long-term complication of SJMS is recurrent pulmonary infections. Sputum culture following by prompt and effective antibiotic therapy along with symptomatic management is the treatment of choice. In most patients with Swyer-James-Macleod syndrome, treatment is managed by chest physiotherapy, low-dose inhaled corticosteroids, and inhaled bronchodilators. Few recent studies have proposed that lung volume reduction surgery (LRS), including pneumonectomy, lobectomy, or segmentectomy, has shown to be effective for improving pulmonary function and symptoms. Physicians should be encouraged to manage the condition as part of an interprofessional team and refer the patients for chest physiotherapy early. Likewise, recognition, when further specialist input is required, and referral for a cardiothoracic opinion, can improve quality of life and prevent serious complications (such as lung abscess or sepsis). Pharmacists review prescriptions, provide education about the use of inhalers, and check for drug-drug interactions. Nurses monitor patients and report status changes to the managing clinicians. [Level 5]
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