Polymorphic variants (e.g., certain alleles of polymorphic markers) that have been found to be associated with high blood eosinophil counts, conditions causative of eosinophilia (e.g., asthma, myocardial infarction), and/or hypertension are provided herein. Such polymorphic markers are useful for diagnostic purposes, such as in methods of determining a susceptibility, and for prognostic purposes, including methods of predicting prognosis and methods of assessing an individual for probability of a response to a therapeutic agent, as further described herein. Further applications utilize the polymorphic markers of the invention include, screening methods and genotyping methods. The invention furthermore provides related kits, computer-readable medium, and apparatus.