Which biopsy helps diagnose eosinophilic esophagitis?

• A. Gastric biopsy
• B. Duodenal biopsy
• C. Esophageal mucosal biopsy showing dense eosinophilic infiltration (≥15 eosinophils per high-power field)
• D. Laryngeal biopsy

Answer: (C)

Eosinophilic esophagitis is diagnosed by histology showing eosinophil-predominant inflammation in the esophageal lining. The hallmark finding is a dense infiltrate of eosinophils in the esophageal mucosa, typically defined as 15 or more eosinophils per high-power field. Obtaining a biopsy from the esophagus and finding this pattern confirms the diagnosis when aligned with compatible symptoms and after ruling out other causes of esophageal eosinophilia. Biopsies from the stomach, duodenum, or larynx do not establish eosinophilic esophagitis, since they reflect disease processes outside the esophagus. In practice, multiple esophageal biopsies from different levels are often taken because eosinophils can be unevenly distributed, and meeting the threshold across samples solidifies the diagnosis.