1 Introduction
Trajectories of allergic diseases follow the paradigm of the atopic
march, which describes the idea of sequential development of allergic
diseases, namely atopic dermatitis (AD), food allergy (FA), allergic
asthma (AA) and allergic rhinitis (AR), in early
life.1 AD, also known as eczema, is a chronic,
recurrent skin disease, characterized by chronic skin barrier
impairment, inflammation of the skin, eczematous lesions and
pruritus.2 AD usually emerges in infancy, arising in
the first year in about 60 % of affected children.3Similarly, primary FA, characterized by IgE-mediated responses to
foods,4 generally arises during infancy and early
childhood.5 AA and AR typically show a later onset and
are thus viewed as the latter manifestations in the trajectory of
allergic diseases.1,5
Dysfunction of the skin barrier, a hallmark of AD, plays an important
role in the aetiology of comorbid allergic diseases. The systemic
sensitization against food allergens and inhalant allergens at a young
age are thought to be promoted by skin barrier impairment (epicutaneous
sensitization), increasing the likelihood for later development of FA,
AA and AR.6
Lately, studies focusing on childhood AD have established the importance
of differentiating between phenotypic subclasses of AD. Typically, these
disease phenotypes are being stratified according to age of onset,
persistence and severity of AD.7-10 Differences in
underlying pathophysiological pathways which might cause this
heterogeneity of AD are yet to be described.8 However,
pinpointing the phenotype at highest risk for developing allergic
multimorbidity and identifying phenotype-specific risk factors is needed
for developing personalized prevention and treatment strategies for
children with AD.
Thus, we hypothesize that children with early onset and persistent
eczema are at highest risk for sensitization against food and/or
inhalant allergens and the subsequent development of allergic
multimorbidity. The current TRACKER (Trajectories of Allergy in Children
in Real Life Databases) study aims to identify the associations of
eczema phenotypes with presence of FA, asthma and hay fever. In
addition, we aimed to describe the trajectories of eczema, asthma and
hay fever, differentiating between children with and without FA.