D1.231 - Endotype-Guided Management of Allergic Asthma in a Pediatric Athlete: Impact of Sublingual Immunotherapy

^{Background: In competitive athletes, asthma may manifest primarily as seasonal performance decline rather than classical symptoms such as recurrent wheeze or marked dyspnea. Near-normal baseline lung function can obscure clinically relevant small airway dysfunction, leading to under-recognition and delayed intervention. Precision medicine requires identification of the dominant inflammatory endotype to enable targeted, disease-modifying therapy.}

^{Case: An 11-year-old competitive endurance athlete was evaluated for recurrent seasonal decline in performance and unexplained fatigue without severe respiratory distress. Baseline spirometry demonstrated near-normal FEV1 (90% predicted), while peak expiratory flow was reduced to 69% predicted and mid-expiratory flow (FEF25–75) was impaired, indicating small airway involvement. Bronchodilator testing increased FEV1 to 100% and PEF to 106%, confirming reversible airflow limitation. Immunologic assessment revealed elevated total IgE, peripheral eosinophilia, and molecular sensitization to early tree pollens including birch (Betula), alder (Alnus), and hazel (Corylus), as well as grass pollens and Alternaria alternata, consistent with an IgE-mediated Type 2 allergic endotype. Treatment with inhaled budesonide/formoterol restored lung function and exercise tolerance.}

^{To modify the underlying allergen-driven inflammation rather than solely control symptoms, sublingual allergen-specific immunotherapy targeting birch, alder, and hazel pollens was initiated after asthma stabilization. During the subsequent pollen season, despite ongoing high-intensity training, lung function remained stable and seasonal performance decline did not recur, with no exacerbations documented.}

^{Conclusion: This case illustrates that seasonal performance decline may represent an early manifestation of allergen-driven small airway dysfunction in pediatric athletes. Endotype-guided integration of sublingual allergen immunotherapy may prevent seasonal functional deterioration beyond pharmacologic symptom control. Early molecular characterization appears essential to optimize personalized management in this population.}