Difficult and Severe Asthma in Children

It is well known that the majority of asthmatic children can be well controlled with basic asthma treatments, mainly represented by inhaled corticosteroids. However, in their daily practice, general pediatricians and specialists need to face patients with problematic asthma which can be clinically challenging, leading to unnecessary over-treatment and resulting in significant utilization of health-care resources. Children suffering from persistent symptoms despite basic asthma treatments are considered as having "difficult to treat asthma". For these patients all differential diagnosis should be ruled out and possible co-morbidities need to be treated. Moreover, all modifiable factors including nonadherence to medication, persistent adverse environmental exposures and psychosocial factors need to be carefully considered. Those patients who remain significantly symptomatic despite these factors having been addressed are considered severe therapy resistant asthmatics (STRA). Although the previous classification seems to be simple, it is definitely more complicated in clinical practice. The correct approach to identify patients that might have true STRA should ideally start in a pediatric clinic, therefore, the initial correct management should be well known by general pediatricians too. However, patients affected by STRA require the time, skill and expertise of respiratory pediatric specialists and a multidisciplinary approach is preferred. Severe pediatric asthma is very different from severe asthma in adults and approaches cannot be extrapolated from adult experience. First of all, lung function tests can be difficult to perform in children and results need a correct interpretation. Many techniques to measure airways obstruction are specific for pediatric age and need to be known by pediatric pulmonologists . Moreover, even though our understanding is still very limited, correct measurements of airway inflammations contribute to identify various phenotypes which have been proven to be distinct from adult patients. Finally, it is widely known that pediatric severe asthma is a markedly heterogeneous disease: asthma hetereogenity is related to different mechanisms and factors – such as infections, allergies and immunological stimuli – playing in the context of a maturing immune system and during lung growth and development. It is important to understand whether those factors are independently associated to asthma or if they contribute synergistically to the development of the disease and to what direction. According to treatment, Omalizumab is currently the only add-on therapy that is licensed for use in children with severe asthma. However, serum IgE levels outside range limitations and lack of clinical efficacy limit its use in more than half of patients. Recently new potential targets have been described for novel therapies but still very little is known.

The aim of this Topic is to provide an update on difficult and severe pediatric asthma. We will focus the readers’ attention on some topics that are essential to understand severe asthma and improve the correct management of patients from diagnosis to treatment. Articles will cover the major topics: the correct diagnostic process, phenotypes and endotypes classification, measurements of airways obstruction and inflammation, major factors involved in pathophysiology and available or new treatment possibilities.