The purpose of this research study is to learn new information about the underlying cause of aspirin-exacerbated respiratory disease (AERD) and the benefit of high-dose aspirin therapy. AERD is a disease that involves asthma, recurring nasal polyps, and respiratory reactions to aspirin and other nonsteroidal anti-inflammatory drugs. This study will be conducted on individuals with AERD who are referred to the Brigham and Women's Hospital AERD Center for clinical evaluation and potential aspirin desensitization. Desensitization to aspirin and subsequent treatment with daily high-dose oral aspirin is standard of care for patients with AERD who do not respond adequately to steroids and have recurrent nasal polyposis or symptomatic asthma. This study will involve five visits to Brigham and Women's Hospital and will align closely with the standard of care for the treatment of AERD.

Inclusion Criteria:

• History of asthma
• History of nasal polyposis
• History of at least one clinical reaction to oral aspirin or other nonselective COX inhibitor with features of both lower (cough, chest tightness, wheezing, dyspnea) and upper (rhinorrhea, sneezing, nasal obstruction, conjunctival itching and discharge) airway involvement
• Stable asthma (post-bronchodilator FEV1 of ≥70%, no use of oral or systemic steroids for at least 1 month, and no hospitalizations or emergency room visits for asthma for the prior 6 months) at the time of entry into the study
• Currently taking montelukast as part of standard asthma treatment for at least 4 weeks before the V1 visit

Exclusion criteria:

• Pregnancy or current breastfeeding
• History of bleeding diathesis or use of anticoagulant or antiplatelet drugs
• History of thrombocytopenia < 50 x 10^9/L
• Hypersensitivity to montelukast
• Peptic ulcer disease
• Unstable asthma (post-bronchodilator FEV1 of less than 70%, use of oral or systemic steroids for at least 1 month prior to visit 1, or hospitalizations or emergency room visits for asthma for the prior 6 months)
• Use of zileuton (which can mask symptoms of aspirin-induced reaction) within 1 month prior to the V1 visit
• Age under 18 or over 75 years
• Current smoking

Patients with aspirin-exacerbated respiratory disease who are undergoing aspirin desensitization and starting high-dose aspirin therapy