Exhaled Nitric Oxide as a Biomarker of Disease Activity in Eosinophilic Esophagitis

There is currently no reliable, noninvasive biomarker for eosinophilic esophagitis (EoE), a
chronic allergic diseases characterized by significant infiltration of eosinophils in the
esophagus. Because eosinophils release nitric oxide, levels of exhaled nitric oxide (FeNO)
are used routinely for guiding treatment in subsets of patients with asthma. FeNO levels are
also elevated in immunological diseases that do not involve the airways. The investigators
hypothesize that patients with EoE have elevated nitric oxide concentration in their exhaled
breath and that changes in FeNO levels could be used to measure disease activity. The
objective of this study is to determine the feasibility of using FeNO as a noninvasive
surrogate marker for EoE disease activity. The investigators propose to measure serial
exhaled nitric oxide (FeNO) levels on a group of patients with confirmed EoE, before, during
and after the course of topical corticosteroid therapy to determine whether the level
declines from pre-treatment level in individual patients.