Functional Dyspepsia (FD) - Clinical Response to Montelukast in Children

Duodenal eosinophilia has been associated with dyspepsia in adults and the investigators have previously described the finding of duodenal mucosal eosinophilia in 71-79% of children undergoing diagnostic endoscopy. Previous studies in children have shown positive response to montelukast with approximately 50% finding complete relief and 20-30 percent showing no response. There are a number of factors that have the potential to contribute to the observed variability in response to montelukast. These include variability in: 1. systemic drug exposure (drug absorption, biotransformation and/or elimination) 2. regulation of leukotriene biosynthesis 3. cysteinyl leukotriene receptors and downstream mediators 4. patient disease phenotype (e.g. Functional Gastrointestinal Disorder (FGID) disease classification, psychologic profile) In this study, the investigators propose to utilize biopsy specimens stratified by drug response to identify candidate gene expression modules that will be validated in a prospective study design. The overall goal of this program is to develop a signature of montelukast response that can be applied not only to eosinophilic gastroenteritis, but more generally to other diseases, such as asthma, where the drug is widely used with variable success.