Marked deposition of eosinophil-derived neurotoxin in adult patients with eosinophilic esophagitis (am j gastroenterol 2010;105:298-307).

A study about eosinophil-derived neurotoxin (EDN) as a biomarker for eosinophilic esophagitis (EoE) has been reported in the February issue of Am J Gastroenterology 2010.1 A diagnostic hallmark of EoE is the number of eosinophils infiltrated in the esophageal epithelium, but there seems to be no universal agreement on either the number or the location of eosinophils required to diagnose EoE. Although the role of eosinophils in the pathophysiology of EoE is not fully understood, eosinophils have a key role in eosinophil related gastrointestinal disease. Therefore eosinophil granule protein and EDN released by eosinophils, and eotaxin-3 have been studied as other possible biomarkers of EoE. Blood, urine or tissue levels of eosinophil granule proteins and EDN are elevated in eosinophilic associated diseases.2-6 However, information regarding localization of EDN in the diseased tissues has not been available. The authors investigated tissue specimens from 10 adult EoE patients and 8 histologically normal controls. Using a polycloncal rabbit antibody to EDN, sections from mid-esophageal biopsy specimens were stained for EDN by immunofluorescence. Cellular staining (infiltration of intact eosinophils) and extracellular staining (deposition of released EDN) were scored in a blinded manner on an established 7-point scale. In the results, esophageal biopsy specimens from normal controls showed no or few intact eosinophils and extracellular EDN depositions. In contrast, EDN staining was clearly observed in specimens from all EoE patients. In some EoE patients, marked extracellular EDN deposition was observed despite a relatively small numbers of intact eosinophils. And there was no correlation between the eosinophil infiltration and the extracellular EDN staining scores. They concluded that tissue eosinophil counts might underestimate how extensively eosinophils are involved, particularly in individuals with marked eosinophil degranulation. Evaluation of EDN in esophageal biopsy specimens was suggested as an useful mean to diagnose and manage patients with EoE.