HRCT represents the diagnostic gold standard of bronchiectasis; however, its use in the paediatric population requires more caution because of the radiation risk. Low-dose CT could represent a valuable alternative, and recent encouraging data suggest that magnetic resonance imaging (MRI) could be promising, particularly for follow-up. However, high cost, technical difficulties and image quality still limit MRI routine use.16,17

The radiological definition of abnormal bronchial dilatation also differs between children and adult: in childhood, bronchiectasis is diagnosed when the broncho-arterial ratio (BAR) is ≥0.8, whereas in adults it ranges from ≥1 to 1.5, depending on series.18 However, it remains unclear when the BAR cut-off for diagnosing the disease should be changed.

Regarding bronchiectasis aetiology, there are some differences between paediatric and adult populations. Idiopathic (unknown cause) and post-infectious are common causes in both age groups, while immunodeficiency, ciliary dyskinesia, congenital malformations, and post-infectious bronchiolitis obliterans are predominant in children.19,20 In adulthood, in addition to these aetiologies, bronchiectasis are often also associated with airways diseases21,22 such as asthma and chronic obstructive pulmonary disease, and other conditions that worsen with ageing, such as autoimmune diseases.

The few data derived from cohorts that include adolescents differ greatly between authors: in a cohort of 8–17-year-old patients, 52.6% of bronchiectasis were classified as idiopathic. Between other aetiologies ciliary dyskinesia was slightly predominant (19.7%), followed by post-infectious disease (15.8%), bronchiolitis obliterans (7.9%) and immunodeficiencies (3.9%).10

In contrast, a more recent series including patients from 14 to 20 years old found that most had post-infective bronchiectasis (94.1%), with only a few cases of conditions typical of childhood, such as chronic neonatal lung disease (2%) and foreign body aspiration (2%), and none were classified as idiopathic.15

Between the 1960s and 70s, longitudinal studies from England (n=225) and Australia (n=69) reported improvement in symptoms from childhood to adolescence, which persisted until the fourth decade of age.8,9 Still, these results are of questionable relevance today: the level of knowledge in bronchiectasis has dramatically improved over the last 20 years, due to the existence of large national and international registries. The availability of national and international guidelines has largely improved bronchiectasis management through the implementation of diagnostic techniques, follow-up methods, treatments, etc. Therefore, the comparison of present data with old ones increases the risk of confusion bias.1,4,5,23–26 Our search identified only two original studies published in the last 30 years reporting data on bronchiectasis clinical history from childhood to adolescence and adulthood.

Kinghorn and colleagues described in 2018 a decrease in exacerbations from childhood to adolescence, although 80% of adolescents with HRCT-confirmed bronchiectasis remained symptomatic (productive cough and/or wheezing), frequently showing obstructive patterns.11

More recently, Sibanda et al. in 2020 reported persistent or intermittent respiratory symptoms in 54% of the 31 adult patients diagnosed in childhood, 13% had severe pulmonary disease, and 23% were asymptomatic. Wheezing was the main symptom reported in adolescence, aligning with Kinghorn's findings.13

Both studies were conducted in a Native Alaska population, whose social, logistic, and genetic peculiarities raise concerns about the large-scale applicability of these findings.

Nevertheless, other authors seem to confirm the “honeymoon” state during adolescence: in a Turkish cohort, most patients between 8 and 17 years were in stable state, with only 6 out of 76 (9.2%) experiencing acute exacerbations. Even if the presence and characteristics of chronic symptoms were not specifically assessed, results of quality of life (QoL) questionnaires suggest patients to be minimally symptomatic. Wheezing was the most frequent issue, whose severity directly correlates with QoL.10

However, it is possible that coping mechanisms during adolescence may influence symptom's referral: adolescents interviewed by Blamires and colleagues referred to coughing as a frequent symptom, but they did not consider it of great significance outside exacerbation. Also, they considered as “normal” the use of 2–4 antibiotic courses per year.14 It is possible that the normalization of symptoms delivers an over optimistic clinical picture of patients, masking the presence of progressive worsening. Hence, instrumental follow-up is important to promptly register changes in clinical status and prevent disease progression, even in patients with mild symptoms.

Lung function tests (LFT), especially spirometry, play an essential role in the follow-up of all patients, although there is no specific lung function impairment pattern for bronchiectasis.27

In the last decade, the implementation of the universal GLI-2012 and Z-scores to interpret LFT has become common in paediatrics,28 while outdated references are still widely used in adult care. During the transition, the shift from one method to the other could lead to misinterpretation of results and prevent early detection of functional decline. Among the papers included in our review, only three reported on lung function.10–12

Moss et al. did not detect any significant trend in lung function over the follow-up period,12 whereas two other series observed reduced FEV1 and FVC despite normal mean FEV1/FVC ratio. However, these data should be considered with caution due to the small sample size.10,11 Moreover, none of these papers used Z-scores to express lung function.

Unlike CF, the natural history of the microbiology of bronchiectasis during adolescence has not yet been described.

In children, literature reports the dominance of Haemophilus spp. (40% of sputum cultures), followed by Streptococcus pneumoniae (20%), Moraxella catarrhalis (8.5%) and Pseudomonas aeruginosa accounting for less than 8% of positive cultures.29 In adults instead, P. aeruginosa plays the prominent role (up to 25%), with Haemophilus influenzae shifting to the second place (23%), followed by Enterobacteriaceae (15%), S. pneumoniae (8%), S. aureus (8%) and M. catarrhalis (5%), with notable regional variations.23

It is unclear what influences this microbiological shift: it could be related to the different distribution of aetiologies, the natural history of the disease with ageing or other unknown factors.

Another crucial difference emerging from our literary review regards the definition of exacerbation and treatment of acute symptoms. In children and adolescents, the n ERS defines a respiratory exacerbation as an increase in respiratory symptoms for at least three days, with or without changes in sputum.4 On the other hand, Hill's criteria in adults define the increase in sputum volume or consistency for 48h or more as one of the fundamental symptoms required to diagnose a respiratory exacerbation.30

Moreover, the recommendation in children is to treat all acute respiratory exacerbations with 14 days of an appropriate systemic antibiotic,4 while in adults, not all exacerbations require antibiotic treatment.30

Therapeutic adherence and readiness for self-care represents another fundamental aspect of the transition process poorly described in the literature. Transitioning from parental care to self-management is delicate and fraught with risks, as seen in other chronic diseases. Moreover, in respiratory diseases like CF or bronchiectasis, adherence to time-consuming treatments, like physiotherapy, airways clearance techniques (ACT) and inhaled antibiotics, is challenging but crucial to ensure clinical stability and prevent functional decline and exacerbations. These treatments often require the interruption of daily life and reorganization of patients’ routine, generating frustration for not being able to attend normal activities such as school, sports, or social events.14 Physiotherapy has been defined by adolescent patients as “a pain”, but the experience of positive results from this self-care helps them in maintaining good adherence and a more conscious and positive attitude to treatment.14

Therefore, physiotherapy and ACT must be tailored to the patient's age and lifestyle, whenever possible, to ensure efficacy and adherence, and specific evidence-based protocols should be designed.31

Psychological preparation and mental health are two of the most critical elements in any transition process. A study published in 2014 observed that depression and anxiety levels in children and adolescents with bronchiectasis were not higher than in the healthy control group. However, bronchiectasis significantly impacted quality of life, correlating with clinical variables and disease severity.10

Interestingly, in another study, 15 bronchiectasis adolescents reported perceiving their life as “pretty normal”, incorporating symptoms and medical care into their daily life.14 Not only age and severity but also healthcare organization and resources influence the experience of children and adolescents throughout their development, with differences depending on geographical and socioeconomic context.

Studies on adolescents with chronic diseases observed reduced adherence to treatment and follow-up when their daily routines are disrupted, for example because of frequent visits or hospitalization.32,33 Transition protocols should take into consideration the need for keeping a normal routine and minimize the impact of treatment and clinical follow-up in school activities.