Mast cells infiltrates are common in eosinophilic esophagitis and still elevated in histological remission: A digital evaluation in children.

Objectives: Eosinophilic esophagitis (EoE) is a type 2 inflammatory chronic allergic disease with several additional immune cell subsets being involved. The aim of this study was to assess the identification and quantification of mast cells (MC) infiltrates using an objective and examiner independent analysis via digital image analysis of digitized histochemically stained biopsies.

Methods: Biopsies were taken from the esophagus of 24 children and adolescents diagnosed with EoE and stained for MC and eosinophilic granulocytes using anti-CD117 and Congo red, respectively. Samples were digitized, eosinophilic granulocytes and MCs were quantified using the MIKAIA® image analysis software.

Results: At diagnosis MC infiltrations were regularly observed in active disease. MC numbers were 160 (cells/mm²) before therapy initiation and 33 (cells/mm²) in histological remission (<15 Eos/HPF). The number of mucosal MCs at the time of remission decreased less than that of eosinophilic granulocytes, regardless of the initiated therapy. Therefore, patients in histological remission with eosinophilic granulocytes showing on average 2,4 cells/mm² still exhibited MC infiltrations (average 33 cells/mm²). Furthermore, male patients displayed higher numbers of eosinophilic granulocytes at time of diagnosis. With regard to the site of biopsy sampling, an accumulation of the MC count in the distal direction can be observed.

Conclusions: Mast cells are involved in EoE and persist after achieving histological remission. Both CD117 + MC and eosinophilic granulocytes can be quantified using MIKAIA® as a tool for objectifying the histological diagnosis of EoE.

Trial registration: Identification number: DRKS-ID 00014688; https://drks.de/search/de/trial/DRKS00014688.