Abstract
House dust mites (HDMs) are the allergenic sources most frequently involved in airway allergy. Nevertheless, not every sensitized patient develops respiratory symptoms upon exposure to HDM, and there is a clinical need to differentiate allergic asthmatics (AAs) from atopic non-allergic asthmatics with HDM sensitization. This differentiation sometimes requires in vivo provocations like the bronchial allergen challenge (BAC). Interestingly, recent data demonstrate that non-atopic patients with asthma can also develop positive BAC results. This novel phenotype has been termed local allergic asthma (LAA). The interest in identifying the allergic triggers of asthma resides in the possibility of administering allergen immunotherapy (AIT). AIT is a disease-modifying intervention, the clinical benefit of which persists after therapy discontinuation. Recently, new modalities of sublingual tablets of HDM immunotherapy registered as pharmaceutical products (HDM-SLIT tablets) have become commercially available. HDM-SLIT tablets have demonstrated a robust effect over critical asthma parameters (dose of inhaled corticosteroids, exacerbations, and safety), thus being recommended by international guidelines for patients with HDM-driven AA. In this review, we will summarize the current knowledge on the phenotype and endotype of HDM-driven AA, and LAA, address the difficulties for BAC implementation in the clinic, and discuss the effects of AIT in AA and LAA.
Highlights
Asthma is an inflammatory condition of the bronchial mucosa affecting 10% of children and 5% of adults in Western countries [1]
These findings demonstrate the allergen specificity of the inflammatory response experienced by bronchial allergen challenges (BAC)-positive individuals, regardless of their atopic status
Given the difficulties to identify bona fide allergic patients among severe asthmatics, in the clinical practice, it is usually accepted that individuals with severe uncontrolled asthma who are sensitized to house dust mites (HDMs) can receive omalizumab
Summary
Asthma is an inflammatory condition of the bronchial mucosa affecting 10% of children and 5% of adults in Western countries [1]. Recent data suggest that HDM can trigger bronchial asthma in non-atopic individuals [8]. This new phenotype has been termed local allergic asthma (LAA). Of note, both AA and LAA are associated to nasal inflammatory diseases, which can be considered their counterparts in the upper airways. Despite not representing a majority of cases, severe asthma accounts for 80% of the costs attributable to the condition, mainly due to repeated exacerbations [2] Allergens, especially those in the feces and bodies of HDM, are known triggers of asthma exacerbations [9], suggesting that allergic mechanisms are essential in severe asthma. This review will summarize the distinct phenotypes of HDM-driven asthma, emphasize the importance of confirming the clinical relevance of immunoglobulin (Ig)E sensitizations, and discuss the many benefits associated with HDM immunotherapy in critical asthma outcomes
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