Upper gastrointestinal mucosal mast cells in infants with persistent distress and gastroesophageal reflux

RATIONALE: We aimed to assess the clinical significance of mucosal mast cells (MC) in the upper gastrointestinal tract of infants with presenting with persistent crying and symptomatic gastroesophageal reflux (GER). METHODS: Forty infants (median age 4 months, range 2-11; 28 male) with persistent distress and symptomatic GER were studied. All infants underwent upper gastrointestinal endoscopy and 24-hour esophageal pH monitoring. Double-blind placebo-controlled challenges (DBPCFC) were performed with cow milk formula vs amino acid-based formula. Immunohistochemical staining for tryptase, a MC specific mediator, was performed on paraffin-embedded esophageal, gastric, and duodenal biopsies, using an anti-tryptase monoclonal antibody. MC's were counted in the entire esophageal epithelium, gastric mucosa and duodenal mucosa (epithelium and lamina propria), and analyzed as cells per mm2. RESULTS: MC numbers were significantly lower in the esophagus (14.8±15.3/mm2) than in the stomach (45.4±14.5/mm2) or duodenum (57.4±33.1/mm2); ANOVA p<0.001. In infants with esophagitis (n=10), there were significantly more epithelial MC than in infants with normal esophageal biopsies (24.0±21.6 vs 9.3±6.8/mm2; p=0.007). In the esophagus, MC numbers correlated well with eosinophils (r=0.785; p<0.001), but not with neutrophil numbers (r=0.152; p=0.41). No correlation was found between mucosal MC numbers and eosinophils in stomach or duodenum. Furthermore, there was no significant difference in MC numbers in esophagus, stomach or duodenum in relation to severity of GER or outcome of DBPCFC. CONCLUSION: The esophageal epithelial MC count was increased in infants with esophagitis and correlated well with epithelial eosinophil numbers. No relationship was found between upper gastrointestinal MC numbers and GER severity or cow milk protein allergy.