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Causes of bronchiectasis in children Authors: Khoulood Fakhoury, MD Adaobi Kanu, MD Section Editor: George B Mallory, MD Deputy Editor: Alison G Hoppin, MD Contributor Disclosures All topics are updated as new evidence becomes available and our peer review process is complete. Literature review current through: Nov 2016. | This topic last updated: Sep 12, 2016. INTRODUCTION — Bronchiectasis is a structural abnormality characterized by abnormal dilation and distortion of the bronchial tree, resulting in chronic obstructive lung disease. This condition is typically the end result of a variety of pathophysiologic processes that render the bronchial walls weakened, easily collapsible, chronically inflamed, and plugged with mucus secretions. In resource-rich countries, cystic fibrosis (CF) is the most common cause of bronchiectasis in children. The evaluation and management of CF-related bronchiectasis is discussed in detail in separate topic reviews. (See"Cystic fibrosis: Clinical manifestations and diagnosis" and "Cystic fibrosis: Clinical manifestations of pulmonary disease" and "Cystic fibrosis: Overview of the treatment of lung disease" and "Cystic fibrosis: Antibiotic therapy for lung disease".) Bronchiectasis can be caused by a variety of disease processes other than CF, most of which include some combination of bronchial obstruction and infection. The types of disorders that cause bronchiectasis vary among populations and age groups. As examples, infections and acquired causes of bronchiectasis predominate in adults and in resource-limited countries, whereas congenital anomalies of the airways or immune system are more prominent in children and resource-rich countries. This topic review will outline the pathogenesis and main causes of non-CF related bronchiectasis in children. The evaluation and management of non-CF bronchiectasis in children, and the causes of bronchiectasis in adults are discussed in separate topic reviews. (See "Clinical manifestations and evaluation of bronchiectasis in children" and "Management of bronchiectasis in children without cystic fibrosis" and "Clinical manifestations and diagnosis of bronchiectasis in adults".) EPIDEMIOLOGY — Prevalence rates vary substantially depending on the method used for case identification. Use of high-resolution computed tomography (CT) will detect milder disease, and result in higher prevalence estimates than strategies employing less sensitive forms of radiography. The estimated prevalence of non-CF bronchiectasis in most populations in most resource-rich countries is low and has gradually declined in recent decades, probably because of improvements in sanitation and housing, immunizations against respiratory illnesses (eg, measles and pertussis), and antibiotic use [1,2]. Reported national incidence of bronchiectasis in children aged 0 to 14 years ranges from 0.5 per 100,000 child-years in Finland [3] to 3.7 per 100,000 child-years in New Zealand [4]. In a study from the United States, non-CF bronchiectasis was diagnosed in only 4.2 per 100,000 young adults [5]. Some indigenous populations, including natives of Polynesia, Alaska, Australia, and New Zealand, have prevalence rates of as high as 15 per 1000 children [6-9]. The relatively high rates of non-CF bronchiectasis in these populations has been attributed to environmental conditions such as overcrowding, poor hygiene, and limited access to health care that are associated with recurrent respiratory infections during childhood, or in some cases to heritable defects in immunity or pulmonary clearance [6,10,11]. PATHOPHYSIOLOGY — Bronchiectasis is the outcome of complex interaction between host, pathogens, and environment [12]. Animal models of bronchiectasis suggest that obstruction, inadequate mucus clearance, and infection are necessary prerequisites [12]. Exposure to pathogens results in an inflammatory response characterized by neutrophil influx and cytokine (inflammatory mediator) release. As examples, proinflammatory mediators (eg, tumor necrosis factor alpha, interleukins 1B and 8) are elevated in the sputum of children with both cystic fibrosis (CF)-related and non-CF related bronchiectasis [13]. Molecular mechanisms that contribute to airway damage in bronchiectasis are discussed in a separate topic review (see "Clinical manifestations and diagnosis of bronchiectasis in adults", section on 'Pathophysiology'). Inflammation also results in impaired mucociliary clearance, which in turn leads to increased bacterial colonization and infection. The continued cycle of infection, inflammation, and airway injury with impaired mucociliary clearance results in loss of the airway muscular and elastic components with dilation and distortion of the airways and increased sputum production. The airways become collapsible, limiting airflow, especially with forced expiration. The lung parenchyma is often involved, developing areas of atelectasis, emphysema, and fibrosis [1,14]. In addition, there is marked hypertrophy of the bronchial vasculature, which is prone to rupture [15]. The classic Reid classification divides bronchiectasis into three different patterns, based on gross histological appearance [16]: ●Cylindrical bronchiectasis, mildly uniform airway dilation ●Varicose bronchiectasis, focally dilated areas between narrowed segments [14,17] ●Saccular bronchiectasis, balloon-like airway dilation with more disruption of lung parenchyma The correlation of these patterns with clinical status, etiology, or pathophysiology is not well established [18]. However, studies using high-resolution computed tomography (CT) scan suggest that bronchiectasis may be a dynamic process, and that cylindrical bronchiectasis can be reversible if the underlying cause is successfully treated (eg, patients with atelectasis, infection, or a retained foreign body) [19-22]. In many other cases, bronchiectatic changes appear to be irreversible. Indeed, some authors propose that the term bronchiectasis be defined as the irreversible dilation of the cartilagecontaining airways or bronchi [23]. The term "traction bronchiectasis" is used to describe the radiological finding of airway widening without surrounding thickening or damage (image 1). This usually is caused by other lung disease, such as interstitial fibrosis, which causes traction on the airway so that it is widened, simulating bronchiectasis. No clinical symptoms are attributed to this finding, although respiratory symptoms related to the underlying disease may be present. (See "Clinical manifestations and diagnosis of bronchiectasis in adults", section on 'Distribution'.) CAUSES — A variety of underlying disease processes can cause bronchiectasis; the cause should be determined whenever possible because this may direct treatment. However, in up to 40 percent of pediatric cases, an underlying cause could not be identified despite a thorough evaluation [24]. As an example, a systematic review of 12 studies with 989 children identified an underlying cause for bronchiectasis in 63 percent of the cases. The most commonly identified causes were previous pneumonia (19 percent), primary immunodeficiency (17 percent), recurrent aspiration, including an inhaled foreign body (10 percent), and primary ciliary dyskinesia (7 percent) [24]. Increased prevalence in certain ethnic groups may indicate genetic basis, but no genome-wide association studies are available [25]. Persistent bacterial bronchitis is a newly recognized entity that may account for some of the cases of bronchiectasis in which an underlying cause cannot be determined. (See 'Infection' below.) The causes of bronchiectasis can be categorized by whether the distribution is localized (focal) or generalized (table 1). This categorization can be helpful in targeting the evaluation. (See "Clinical manifestations and evaluation of bronchiectasis in children".) The causes of bronchiectasis also can be categorized according to the underlying pathophysiology (table 2): ●Congenital bronchiectasis ●Bronchial narrowing or obstruction ●Immunodeficiency ●Abnormal secretion clearance (leading to chronic airway infection) ●Infection ●Other underlying disorders Congenital bronchiectasis — Two congenital disorders have been described in which the structural rigidity of the tracheobronchial tree is compromised, leading to congenital bronchiectasis: ●Williams-Campbell syndrome is a rare congenital disorder characterized by deficient cartilage in the bronchial tree, causing generalized tracheobronchomalacia [26]. Because the bronchial cartilage is absent or deficient, the segmental and subsegmental bronchi are dilated and collapse easily. Children typically present before three years of age with cough, wheezing, and recurrent febrile illness. Based on the few cases reported in the literature, the prognosis is variable. ●Congenital tracheobronchomegaly (Mounier-Kuhn syndrome) is a congenital disorder that is characterized by markedly dilated trachea and main bronchi, resulting in dynamic dilation and collapse during inspiration and exhalation. On pathologic examination, there is atrophy or absence of elastic tissue, and thinning of the muscular components of the airway. Outpouching of redundant mucosal tissue results in pooling of secretions and recurrent infection, leading to bronchiectasis. The clinical manifestations range from minimal disease to respiratory failure and death. (See "Tracheomalacia and tracheobronchomalacia in adults", section on 'Congenital'.) Bronchial narrowing or obstruction — Bronchial obstruction or narrowing may result in poor mucociliary clearance and chronic infection, with subsequent development of bronchiectasis. This can be congenital or acquired: Congenital airway or bronchial obstruction — Causes of congenital bronchial obstruction include: ●Congenital airway malacia (tracheomalacia and bronchomalacia) — These disorders can be caused by primary defects in the airway wall, or may be secondary to external compression by another structure, such as a vascular ring or sling or pulmonary artery dilatation. Occasionally, the obstruction is severe enough to lead to recurrent infections and bronchiectasis. (See "Congenital anomalies of the intrathoracic airways and tracheoesophageal fistula", section on 'Tracheomalacia' and "Congenital anomalies of the intrathoracic airways and tracheoesophageal fistula", section on 'Bronchomalacia'.) ●Tracheal or bronchial stenosis (see "Congenital anomalies of the intrathoracic airways and tracheoesophageal fistula") ●Bronchogenic cyst (see "Congenital anomalies of the intrathoracic airways and tracheoesophageal fistula", section on 'Bronchogenic cyst') ●Tracheal bronchus (ectopic bronchus) (see "Congenital anomalies of the intrathoracic airways and tracheoesophageal fistula", section on 'Tracheal bronchus') ●Bronchopulmonary sequestration (intralobar type) (see "Bronchopulmonary sequestration") ●Congenital pulmonary airway malformation (CPAM), formerly known as congenital cystic adenomatoid malformation (CCAM) (see "Congenital pulmonary airway (cystic adenomatoid) malformation") Acquired bronchial obstruction ●Foreign body aspiration — The most common cause of localized bronchiectasis in previously healthy children is endobronchial obstruction due to foreign body aspiration, most often of food items that are not radio-opaque, such as peanuts [27]. The child typically presents with a sudden onset of cough, which persists over time. The aspiration event may have occurred weeks or even months prior to presentation, so a history of choking may not be recalled. The clinical course can be complicated by pneumonia, pneumothorax, hemoptysis, and bronchiectasis (algorithm 1) [28]. (See "Airway foreign bodies in children".) ●Mucoid impaction — A variety of disorders tend to cause mucus plugging. If the plugging is prolonged or recurrent, it can lead to bronchiectasis. •Middle lobe syndrome is a pattern of chronic or recurrent atelectasis that usually affects the right middle or left lingular lobes of the lung. In children, it is usually seen in asthmatics. Although respiratory symptoms may improve after recovery from an asthma exacerbation, the atelectatic lobe may not re-expand, resulting in repeated episodes of obstruction, infection, and inflammation that may eventually lead to bronchiectasis [29-32]. (See "Atelectasis in children", section on 'Obstructive atelectasis'.) (image 2) [33,34] •Allergic bronchopulmonary aspergillosis, a pulmonary hypersensitivity reaction to Aspergillus fumigatus, causes intense chronic airway inflammation. Repeated episodes of inflammation, mucoid impaction, and bronchial obstruction can lead to central bronchiectasis, fibrosis, and respiratory compromise (image 2). This disorder typically occurs in patients with asthma and cystic fibrosis [33,34]. (See "Clinical manifestations and diagnosis of allergic bronchopulmonary aspergillosis".) •Bronchocentric granulomatosis is a destructive, granulomatous lesion of the bronchi and bronchioles that is generally believed to represent a nonspecific response to a variety of types of airway injury. Approximately half of all cases are associated with asthma and allergic bronchopulmonary aspergillosis (ABPA). (See "Bronchocentric granulomatosis".) Other causes of airway obstruction that can result in bronchiectasis in the pediatric population include granulomatous diseases of the airway (eg, tuberculosis) and lymph node enlargement [15]. Airway tumors are rare in children. (See "Clinical manifestations and diagnosis of bronchiectasis in adults".) Immunodeficiency states — Congenital and acquired immunodeficiency disorders predispose the host to recurrent infections and to the development of bronchiectasis, including the following: ●HIV infection [35,36] (see "Pediatric HIV infection: Classification, clinical manifestations, and outcome") ●X-linked agammaglobulinemia (see "Agammaglobulinemia") ●IgG subclass deficiencies (see "Primary humoral immunodeficiencies: An overview") ●Common variable immunodeficiency (see "Common variable immunodeficiency in children") ●DiGeorge syndrome (thymus hypoplasia) (see "DiGeorge (22q11.2 deletion) syndrome: Management and prognosis") ●Severe combined immunodeficiency (SCID) (see "Severe combined immunodeficiency (SCID): An overview") ●Other combined immunodeficiencies (see "Combined immunodeficiencies") ●Complement deficiencies (see "Inherited disorders of the complement system") ●Chronic granulomatous disease (CGD) and other disorders causing leukocyte dysfunction (see "Primary disorders of phagocytic function: An overview" and "Chronic granulomatous disease: Pathogenesis, clinical manifestations, and diagnosis") ●Major histocompatibility complex (MHC, also known as HLA) deficiencies cause bare lymphocyte syndrome, which is often associated with mutations in the Transporter associated with Antigen Presentation (TAP) gene [37-39]. (See "CD3/T cell receptor complex disorders causing immunodeficiency".) The type of pulmonary infection varies depending on the nature of the immunodeficiency. (See "Approach to the child with recurrent infections" and "Primary humoral immunodeficiencies: An overview".) Bronchiectasis has occasionally been reported in patients with selective IgA deficiency, which is the most common immune deficiency disorder [40]. However, it is not clear whether this is a true association. (See"Selective IgA deficiency: Clinical manifestations, pathophysiology, and diagnosis", section on 'Sinopulmonary'.) Abnormal secretion clearance — Disorders in which clearance of secretions from the airways is impaired predispose to recurrent pulmonary infection and thus to bronchiectasis. Because these disorders usually affect the entire airway, the infection and bronchiectasis tend to be diffusely distributed. ●Cystic fibrosis (CF) is the most common cause of bronchiectasis in resource-rich countries; it is a less predominant cause in resource-limited countries or indigenous populations, in which infectious causes of bronchiectasis are more common [15]. Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene result in abnormal ion and water transport across the respiratory epithelial cell, resulting in thick, desiccated mucus. Airway obstruction with mucus and poor mucociliary clearance allows bacterial infection to occur, causing inflammation and subsequent airway damage. (See "Cystic fibrosis: Clinical manifestations and diagnosis".) ●Primary ciliary dyskinesia (PCD) is a disorder of ciliary function due to ultrastructural defects of the cilium (most commonly the outer dynein arms). Half of the patients with PCD have situs inversus (Kartagener syndrome). Children typically present with recurrent sinusitis, otitis media, and recurrent pneumonia due to impaired ciliary function, and bronchiectasis ultimately occurs in most of these patients [41]. (See "Primary ciliary dyskinesia (immotile-cilia syndrome)".) ●Young's syndrome is characterized by obstructive azoospermia and sinopulmonary infections, but no identifiable ciliary dysfunction or structural defect [42]. Mucociliary clearance is impaired, and bronchiectasis has been reported [43]. Some cases may have been caused by mercury exposure during childhood; other reported cases of Young's syndrome may be atypical variants of CF or PCD [44-46]. (See"Clinical manifestations and diagnosis of bronchiectasis in adults", section on 'Young syndrome'.) ●Patients with muscular dystrophies and other diseases with neuromuscular weakness often have impaired mucus clearance, due to ineffective cough and chest wall deformities, which can lead to recurrent pulmonary infection and bronchiectasis. (See "Clinical features and diagnosis of Duchenne and Becker muscular dystrophy".) Infection — In resource-limited countries and some indigenous populations, chronic and/or undertreated pulmonary infection remains a common cause of bronchiectasis in children [1,15,29]. In most populations in resource-rich countries, infection is not as common a cause of bronchiectasis unless there is an underlying anatomic or immunologic defect. ●Persistent bacterial bronchitis (PBB) is increasingly recognized as a cause of chronic wet cough, particularly in young children. Identification and treatment of PBB is important because it may be a precursor to chronic suppurative lung disease, including bronchiectasis. In some indigenous populations, PBB may be an important cause of bronchiectasis previously thought to be "idiopathic" [6-8]. However, the prevalence of PBB and association with bronchiectasis is difficult to establish, because the bacterial infection is rarely confirmed. (See "Causes of chronic cough in children", section on 'Protracted bacterial bronchitis'.) ●Pneumonia — Bacterial pneumonia occasionally leads to bronchiectasis, particularly if recurrent or associated with an underlying anatomic or immune defect. Mycoplasma pneumonia usually has a benign course. However, in a series of 38 children hospitalized with mycoplasma pneumonia, eight were found to have bronchiectasis when evaluated with high resolution CT (HRCT) scan after long-term follow up [47]. (See "Mycoplasma pneumoniae infection in children", section on 'Radiographic features'.) ●Childhood infections with pertussis and measles have been associated with the development of bronchiectasis [48,49]. In a series of children with bronchiectasis diagnosed between 1946 and 1955, bronchiectasis was frequently preceded by an infection with pertussis (21 percent) or measles (14 percent) [48]. However, since the advent of routine vaccinations, the incidence of these childhood infections has markedly decreased. (See "Measles: Clinical manifestations, diagnosis, treatment, and prevention", section on 'Complications' and "Pertussis infection in infants and children: Clinical features and diagnosis".) ●Adenovirus infection, especially the type 7 strain, has been associated with bronchiectasis [50] and abnormal lung function [51]. In addition, adenovirus has been associated with the development of Swyer James syndrome, which is characterized by unilateral small hyperlucent lung with bronchiectasis and diminished arterial supply [52]. Swyer James syndrome has also been associated with other viral infections, pertussis, foreign body and hydrocarbon ingestion [52-54]. (See "Congenital lobar emphysema", section on 'Differential diagnosis'.) ●Mycobacterial infection — Tuberculosis remains an important cause of bronchiectasis in children from endemic countries and in children with HIV infection [8,29] (see "Tuberculosis disease in children"). Mycobacterium avium-intracellulare complex (MAC), an opportunistic infection usually associated with immunodeficiencies such as HIV infection, results in lung pathology including adenopathy, cavitation, and bronchiectasis [36]. (See "Mycobacterium avium complex (MAC) infections in HIV-infected patients".) ●Recurrent aspiration — Chronic aspiration of gastric contents or secretions may occur in patients with neurologic disease and in congenital disorders, such as tracheoesophageal fistula [55-57]. This may result in a variety of respiratory symptoms and diseases, including apnea, laryngospasm, chronic cough, asthma, pneumonia, and bronchiectasis. In children without neurologic dysfunction or anatomic abnormalities, gastroesophageal reflux disease (GERD) appears to be associated with a modestly increased risk of bronchiectasis [55]. (See "Aspiration due to swallowing dysfunction in infants and children" and "Clinical manifestations and diagnosis of gastroesophageal reflux disease in children and adolescents", section on 'Recurrent pneumonia'.) Other disorders ●Bronchiolitis obliterans describes a pattern of histologic abnormalities affecting the small airways. It is a common complication of chronic rejection of lung transplantation, due to chronic rejection. It also may be seen in the context of bone marrow transplantation, interstitial lung disease, or as a post-infectious process. (See "Chronic lung transplant rejection: Bronchiolitis obliterans".) ●Connective tissue disorders, particularly systemic lupus erythematosus (SLE), can be complicated by bronchiectasis. More than half of adult patients with SLE have thoracic involvement, which may include primary disease, such as alveolitis or interstitial lung disease (ie, bronchiolitis obliterans with organizing pneumonia), or atelectasis caused by diaphragmatic dysfunction [18,58]. In one series, bronchiectasis was detected by HRCT scan in 21 percent of adult patients with SLE [59]. (See "Systemic lupus erythematosus (SLE) in children: Clinical manifestations and diagnosis", section on 'Pulmonary disease'.) ●Sarcoidosis is a multisystem granulomatous disorder of unknown etiology that is typically first diagnosed during adolescence or young adulthood. The disease often causes granulomatous inflammation of the bronchial mucosa, peribronchial, perivascular, and subpleural areas of the lung [18]. Mild bronchiectasis has been described in an adolescent with sarcoidosis [60]. Bronchoscopy and bronchography in adult patients with sarcoidosis suggest that bronchiectasis may be caused by airway wall destruction and weakening by granulomas, or by distortion of the airway by pulmonary fibrosis [61]. (See "Clinical manifestations and diagnosis of pulmonary sarcoidosis".) ●Marfan syndrome is an inherited abnormality of connective tissue. In a case series of 100 patients with Marfan syndrome, five had pneumonia, three had history of frequent lower respiratory tract illness, and two had bronchiectasis [62]. (See "Genetics, clinical features, and diagnosis of Marfan syndrome and related disorders".) ●Inflammatory bowel disease (IBD) is frequently associated with extra-intestinal involvement, including joints, skin, and eyes [63]. Rarely, pulmonary disease may occur, including airway inflammation and parenchymal disease. Subglottic stenosis, chronic bronchitis associated with bronchiectasis, and interstitial lung disease including bronchiolitis obliterans with organizing pneumonia have been observed [64]. Among children with IBD, bronchiectasis is rare but has been reported [65]. (See "Pulmonary complications of inflammatory bowel disease".) INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon. Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.) ●Basics topic (see "Patient education: Bronchiectasis in children (The Basics)") SUMMARY ●Bronchiectasis is characterized by abnormal dilation and distortion of the bronchial tree, resulting in chronic obstructive lung disease. This condition is the end result of a variety of pathophysiologic processes, usually including some combination of infection and impaired mucus drainage or airway obstruction. (See 'Pathophysiology' above.) ●In resource-rich countries, cystic fibrosis (CF) is the most common cause of bronchiectasis in children. The evaluation and management of CF-related bronchiectasis is discussed in detail in separate topic reviews. (See "Cystic fibrosis: Clinical manifestations and diagnosis" and "Cystic fibrosis: Clinical manifestations of pulmonary disease".) ●The prevalence of non-CF related bronchiectasis in most populations in resource-rich countries is low. However, some indigenous populations have prevalence rates of as high as 15 per 1000 children. (See'Epidemiology' above.) ●Non CF-related bronchiectasis can be caused by a variety of pathogenic processes (table 2). In children, important or common causes of bronchiectasis include: •Immunodeficiency states (eg, agammaglobulinemia or IgG subclass deficiencies, or common variable immunodeficiency). (See 'Immunodeficiency states' above and "Approach to the child with recurrent infections".) •Primary ciliary dyskinesia. (See 'Abnormal secretion clearance' above and "Primary ciliary dyskinesia (immotile-cilia syndrome)".) •Infections such as persistent bacterial bronchitis, recurrent pneumonia, adenovirus or other childhood viral illnesses. (See 'Infection' above.) •Foreign body aspiration. Bronchiectasis associated with foreign body aspiration is usually focal or localized. (See 'Acquired bronchial obstruction' above and "Airway foreign bodies in children".) •Congenital anomalies of the intrathoracic airways. (See 'Bronchial narrowing or obstruction' above and"Congenital anomalies of the intrathoracic airways and tracheoesophageal fistula".) •Bronchiolitis obliterans (most commonly seen as a complication of lung transplantation). ●The causes of bronchiectasis can also be categorized by their characteristic distribution (eg, focal versus generalized) (table 1). This categorization can be helpful in targeting the evaluation. (See 'Causes' above and "Clinical manifestations and evaluation of bronchiectasis in children".) Use of UpToDate is subject to the Subscription and License Agreement. REFERENCES 1. 2. 3. 4. 5. 6. Kumar NA, Nguyen B, Maki D. Bronchiectasis: current clinical and imaging concepts. 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