BackgroundAllergen exposure leads to allergen sensitization in susceptible individuals and this might influence allergic rhinitis (AR) phenotype expression. We investigated whether sensitization patterns vary in a country with subtropical and tropical regions and if sensitization patterns relate to AR phenotypes or age.MethodsIn a national, cross-sectional study AR patients (2-70 y) seen by allergists underwent blinded skin prick testing with a panel of 18 allergens and completed a validated questionnaire on AR phenotypes.Results628 patients were recruited. The major sensitizing allergen was house dust mite (HDM) (56%), followed by Bermuda grass (26%), ash (24%), oak (23%) and mesquite (21%) pollen, cat (22%) and cockroach (21%). Patients living in the tropical region were almost exclusively sensitized to HDM (87%). In the central agricultural zones sensitization is primarily to grass and tree pollen. Nationwide, most study subjects had perennial (82.2%), intermittent (56.5%) and moderate-severe (84.7%) AR. Sensitization was not related to the intermittent-persistent AR classification or to AR severity; seasonal AR was associated with tree (p < 0.05) and grass pollen sensitization (p < 0.01). HDM sensitization was more frequent in children (0-11 y) and adolescents (12-17 y) (subtropical region: p < 0.0005; tropical region p < 0.05), but pollen sensitization becomes more important in the adult patients visiting allergists (Adults vs children + adolescents for tree pollen: p < 0.0001, weeds: p < 0.0005).ConclusionsIn a country with (sub)tropical climate zones SPT sensitization patterns varied according to climatological zones; they were different from those found in Europe, HDM sensitization far outweighing pollen allergies and Bermuda grass and Ash pollen being the main grass and tree allergens, respectively. Pollen sensitization was related to SAR, but no relation between sensitization and intermittent-persistent AR or AR severity could be detected. Sensitization patterns vary with age (child HDM, adult pollen). Clinical implications of our findings are dual: only a few allergens –some region specific- cover the majority of sensitizations in (sub)tropical climate zones. This is of major importance for allergen manufacturers and immunotherapy planning. Secondly, patient selection in clinical trials should be based on the intermittent-persistent and severity classifications, rather than on the seasonal-perennial AR subtypes, especially when conducted in (sub)tropical countries.

What is already known about this topic? A phase III study demonstrated that compared with placebo, 4-weekly add-on mepolizumab (300 mg subcutaneously) reduced flares in patients with uncontrolled FIP1-like-1-platelet-derived growth factor receptor a (FIP1L1-PDGFRA)-negative hypereosinophilic syndrome (HES), with a positive benefiterisk profile.What does this article add to our knowledge? This open-label extension study found no new safety signals with mepolizumab treatment in patients with FIP1L1-PDGFRA-negative HES. Moreover, mepolizumab continued to control flares and blood eosinophil counts after 52 weeks of continuous treatment.How does this study impact current management guidelines? Findings from this open-label extension study provide further evidence that patients with FIP1L1-PDGFRA-negative HES are likely to benefit from treatment with mepolizumab and may be able to reduce oral corticosteroid use.BACKGROUND: A double-blind, placebo-controlled, phase III study (200622) showed that mepolizumab reduces disease flares for patients with uncontrolled FIP1-like-1-platelet-derived growth factor receptor aenegative hypereosinophilic syndrome (HES) and two or more flares in the previous year. OBJECTIVE: To further characterize the safety, clinical benefit, and pharmacodynamics of mepolizumab. METHODS: Eligible patients from both treatment arms of the double-blind study could enter an open-label extension study (205203; NCT03306043) to receive 4-weekly mepolizumab (300 mg subcutaneously) plus background therapy for 20 weeks. Primary end points were safety-based; other end points included flare rates and changes from baseline in mean daily oral corticosteroid (OCS) dose and blood eosinophil count. RESULTS: Of 104 patients who completed the double-blind study, 98% (previous placebo, n [ 52; previous mepolizumab, n [ 50) enrolled in the open-label extension. Overall, 66 of patients reported adverse events (AEs) (65%), 15 reported

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