10.1586/ERS.12.68 629 ISSN 1747-6348 © 2012 Expert Reviews Ltd www.expert-reviews.com Review Asthma is the most common respiratory chronic disease of childhood: its prevalence has been ris- ing in the western world for the last three dec- ades, up to the point to currently affect a pro- portion of children as high as 10% in the USA [1,201] . It is a heterogeneous condition expressed through a plethora of phenotypes that mir- ror diverse, not fully characterized underlying mechanisms. From this perspective, the defi- nition of asthma as a syndrome rather than a single entity would do justice to the multitude of immunologic, mechanistic and structural factors that orchestrate its pathogenesis. These multiple facets of asthma, perplex both charac- terization of the disease and the streamlining of efficient treatment measures. Furthermore, the inherent difficulty in illustrating pediat- ric asthma mechanics (owing to continuously ongoing maturation processes and consider- able overlap between diverse phenotypes), fur- ther impedes our understanding of the disease in this age group. Asthma exacerbations, for example, are sudden-onset, episodic deterio- rations of preexisting disease, and a key cause for anxiety and impaired quality of life in this particularly susceptible age group. Although the clinical manifestations of a severe asthma exac- erbation are fairly obvious, they are not specific; moreover, pediatric patients demonstrating more subtle symptoms could pose a diagnostic chal- lenge. Indeed, they commonly present with vari- ous nonpathognomonic complaints, including wheezing, cough and respiratory distress. Such a clinical picture could very well fit other patho- logic entities that do not warrant treatment on an emergency basis, including respiratory tract infections, laryngomalacia/tracheomalacia, pri- mary ciliary dyskenisia, vocal-cord dysfunction, structural abnormalities of the upper and lower airway, mechanical obstruction, cystic fibrosis, bronchiolitis, acute wheeze and post-bronchioli- tis wheeze [2] . Nevertheless, in contrast to many of these conditions, a severe asthma exacerba- tion has the potential to rapidly culminate in life-threatening respiratory compromise. Indeed, notwithstanding the last decade’s advances in our knowledge of asthma pathophysiology, acute exacerbations remain a source of considerable morbidity for patients and financial burden for healthcare systems [1] . Efficient prevention of acute asthma attacks depends on factors such as severity, control of the underlying disease and the definition used for exacerbations [3] . In effect, the lack of objective criteria and of a uniformly accepted definition for an asthma exacerbation impedes our efforts to prevent such events. Therefore, a concise characterization of what is essentially an abrupt and severe wors- ening of asthma symptoms is of importance. Accordingly, acute asthma exacerbations have been defined as ‘episodes of progressive short- ness of breath, cough, wheezing and chest tight- ness presented individually or in combination’ [4] . Nevertheless, this definition cannot clearly George V Guibas 1 , Michael Makris 1 and Nikolaos G Papadopoulos* 2 1 Allergy Unit ‘D. Kalogeromitros’, Attikon University Hospital, University of Athens Medical School, Athens, Greece 2 Allergy Department, 2nd Pediatric Clinic, University of Athens Medical School, Athens, Greece *Author for correspondence: ngp@allergy.gr Asthma is a heterogeneous disease more appropriately seen as a syndrome rather than a single pathologic entity. Although it can remain quiescent for extended time periods, the inflammatory and remodeling processes affect the bronchial milieu and predispose to acute and occasionally severe clinical manifestations. The complexity underlying these episodes is enhanced during childhood, an era of ongoing alterations and maturation of key biological systems. In this review, the authors focus on such sudden-onset events, emphasizing on their diversity on the basis of the numerous asthma phenotypes. Acute asthma exacerbations in childhood: risk factors, prevention and treatment Expert Rev. Respir. Med. 6(6), 629–638 (2012) KEYWORDS:฀asthma฀•฀children฀•฀deinition฀•฀exacerbations฀•฀phenotypes฀•฀prevention฀•฀treatment For reprint orders, please contact reprints@expert-reviews.com