Mast Cell Infiltration Is Associated With Persistent Symptoms and Endoscopic Abnormalities Despite Resolution of Eosinophilia in Pediatric Eosinophilic Esophagitis

Mast Cell Esophagitis: A Novel Entity in Patients with Unexplained Esophageal Symptoms

It is not known whether esophageal mast cells may be a cause of unexplained esophageal symptoms. We aimed to determine the prevalence of esophageal mastocytosis in patients without other underlying causes of symptoms and assess the relationship between symptoms and mast cells. In this retrospective study, we identified adults with esophageal symptoms, a normal endoscopy, normal esophageal biopsies, and no definitive diagnosis during clinical evaluation. We quantified mast cell density (mast cells/mm2) in archived esophageal biopsies using tryptase immunohistochemistry, and compared mast cell levels by clinical features and physiologic testing. In the 87 patients identified (mean age 37, 72% female, 63% white, 92% non-Hispanic), common symptoms were dysphagia (76%), heartburn (71%), and chest pain (25%). Overall, the mean esophageal epithelial mast cell count was 83.0 ± 51.8 mast cells/mm2; 60% of patients had ≥ 60 mast/mm2, and 17% had ≥ 120 masts/mm2. There were no differences in mast cell counts by type of esophageal testing. Mast cell levels did not differ significantly by type of symptoms, atopic status, medications, smoking status, or alcohol use. There were also no major differences in clinical characteristics by mast cell quartiles or thresholds. In conclusion, esophageal mast cell infiltration was common in patients with symptoms unexplained by prior testing, and levels were higher than previously published values for patients with no underlying esophageal condition. Mast cell esophagitis could be a novel cause of unexplained esophageal symptoms in a subset of patients, though it reamins to be determined if such patients benefit from mast cell-targeted treatment.

Expression of CD25, mast cell markers and T-cell markers in eosinophilic esophagitis

While eosinophilic esophagitis (EOE) is defined by histologic presence of eosinophils, a few studies have established the presence of mast cells in EOE and even shown their correlation with symptom persistence despite resolution of eosinophils. Expression of aberrant mast cell markers CD25 and CD2 have not been studied in EOE. This study quantifies the number of hotspot cells per high power field expressing CKIT/CD117, tryptase, CD25, CD2 and CD3 by immunohistochemical stains in endoscopic esophageal biopsies of the following three cohorts: (1) established and histologically confirmed EOE, (2) suspected EOE with biopsies negative for eosinophils, and (3) no history of or suspicion for EOE with histologically unremarkable biopsies. In this study, mast cells were highlighted by CKIT and tryptase in EOE, and not seen in other clinically mimicking cases. There were also significantly higher densities of CD25 and pan-T-cell marker staining in EOE cases. These findings suggest an inflammatory cellular milieu in EOE, beyond just eosinophils, that can be demonstrated by immunohistochemistry, and that invite further study into the role that these cells may play in EOE.

Common and disparate clinical presentations and mechanisms in different eosinophilic gastrointestinal diseases

Eosinophilic gastrointestinal diseases (EGIDs) are a group of diseases characterized by selective eosinophil infiltration of the gastrointestinal (GI) tract in the absence of other causes of eosinophilia. These diseases are generally driven by type 2 inflammation, often in response to food allergen exposure. Among all EGIDs, the clinical presentation often includes a history of atopic disease with a variety of GI symptoms. EGIDs are traditionally separated into eosinophilic esophagitis (EoE) and non-EoE EGIDs. EoE is relatively better understood and now associated with clinical guidelines and 2 US Food and Drug Administration-approved treatments, whereas non-EoE EGIDs are rarer and less well-understood diseases without US Food and Drug Administration-approved treatments. Non-EoE EGIDs are further subclassified by the area of the GI tract that is involved; they comprise eosinophilic gastritis, eosinophilic enteritis (including eosinophilic duodenitis), and eosinophilic colitis. As with other GI disorders, the disease presentations and mechanisms differ depending on the involved segment of the GI tract; however, the differences between EoE and non-EoE EGIDs extend beyond which GI tract segment is involved. The aim of this article is to summarize the commonalities and differences between the clinical presentations and disease mechanisms for EoE and non-EoE EGIDs.

Transnasal Endoscopy Acquires Esophageal Biopsies Adequate for Comprehensive Pathology Evaluation in Patients With Eosinophilic Esophagitis

BACKGROUND

Transnasal endoscopy (TNE) does not require general anesthesia, an attractive characteristic for monitoring eosinophilic esophagitis (EoE). We evaluated the adequacy of TNE-obtained esophageal biopsies using the EoE Histology Scoring System (EoEHSS).

METHODS

The Cincinnati Center for Eosinophilic Disorders database was searched for esophageal biopsies obtained by the same endoscopist, using either TNE or conventional endoscopy (CE). Whole-slide biopsy images were evaluated. The Mann-Whitney test was used for median (interquartile range) values and Fisher exact test for categorical variables. P ≤ .05 was considered significant.

RESULTS

Median age (P = .82) or height (P = .83) did not differ between TNE (n = 17) and CE (n = 17) groups. Although median largest piece size (mm2) differed between the groups (TNE: 0.59 (0.45, 0.86), CE: 2.24 (1.09, 2.82), P < .001), all 8 EoEHSS features were evaluated in each group; only 1 feature (lamina propria fibrosis) was missing in both groups (TNE: 19/34, CE: 11/34, P = .09). The median peak eosinophil count/high-power field differed (TNE: 3 (0, 29), CE: 16 (1, 66), P = .03), but overall grade (TNE: 0.17 (0.10, 0.29), CE: 0.22 (0.14, 0.46), P = .12), stage (TNE: 0.14 (0.10, 0.24), CE: 0.20 (0.10, 0.43), P = .15), and non-eosinophil-related individual EoEHSS scores did not differ.

CONCLUSIONS

TNE- and CE-obtained esophageal biopsies are similarly sufficient for evaluation of key pathological features in EoE.

Machine learning-based identification and characterization of mast cells in eosinophilic esophagitis

BACKGROUND

Eosinophilic esophagitis (EoE) is diagnosed and monitored using esophageal eosinophil levels; however, EoE also exhibits a marked, understudied esophageal mastocytosis.

OBJECTIVES

Using machine learning, we localized and characterized esophageal mast cells (MCs) to decipher their potential role in disease pathology.

METHODS

Esophageal biopsy samples (EoE, control) were stained for MCs by anti-tryptase and imaged using immunofluorescence; high-resolution whole tissue images were digitally assembled. Machine learning software was trained to identify, enumerate, and characterize MCs, designated Mast Cell-Artificial Intelligence (MC-AI).

RESULTS

MC-AI enumerated cell counts with high accuracy. During active EoE, epithelial MCs increased and lamina propria (LP) MCs decreased. In controls and EoE remission patients, papillae had the highest MC density and negatively correlated with epithelial MC density. MC density in the epithelium and papillae correlated with the degree of epithelial eosinophilic inflammation, basal zone hyperplasia, and LP fibrosis. MC-AI detected greater MC degranulation in the epithelium, papillae, and LP in patients with EoE compared with control individuals. MCs were localized further from the basement membrane in active EoE than EoE remission and control individuals but were closer than eosinophils to the basement membrane in active EoE.

CONCLUSIONS

Using MC-AI, we identified a distinct population of homeostatic esophageal papillae MCs; during active EoE, this population decreases, undergoes degranulation, negatively correlates with epithelial MC levels, and significantly correlates with distinct histologic features. Overall, MC-AI provides a means to understand the potential involvement of MCs in EoE and other disorders.

Histopathology of Eosinophilic Esophagitis

Microscopic examination of esophageal biopsies is essential to diagnose eosinophilic esophagitis (EoE). Eosinophil inflammation is the basis for the diagnosis, but additional abnormalities may contribute to persistent symptoms and epithelial barrier dysfunction. Both peak eosinophil count and assessments of additional features should be included in pre-therapy and post-therapy pathology reports. Pathologic abnormalities identified in esophageal biopsies of EoE are reversible in contrast to esophageal strictures.

Minimally Invasive Approaches to Diagnose and Monitor Eosinophilic GI Diseases

PURPOSE OF REVIEW

This review seeks to understand novel avenues for eosinophilic GI disease management. Biomarkers offer a unique and non-invasive approach to tracking EoE disease progression. While no biomarkers have definitively met the diagnostic criteria for eosinophilic GI diseases, some biomarkers have been shown to be associated with disease activity. Here, we examine the potential of recently studied biomarkers.

RECENT FINDINGS

Current research shows advancements in blood, luminal fluid, and breath testing. Particular areas of interest include mRNA analyses, protein fingerprinting, amplicon sequence variants (ASVs), T cells and IgE receptors, eosinophilic cationic proteins, cytokines, and nitric oxide exhalation. Preliminary results showed that mucosal biomarkers, directly captured from the esophagus, may reflect the best representation of biopsy-based results, in contrast to biomarkers obtained from indirect or peripheral (blood, breath) methods. However, this is based on limited clinical studies without sufficient numbers to evaluate true diagnostic accuracy. Large-scale randomized trials are needed to fully ascertain both the optimal sampling technique and the specific biomarkers that reflect diagnostic status of the disease.

Role of Mast Cells in Eosinophilic Gastrointestinal Diseases

Mast cells play a central role in the pathogenesis of eosinophilic gastrointestinal disorders (EGIDs), including eosinophilic esophagitis. Their interactions with immune and structural cells, involvement in tissue remodeling, and contribution to symptoms make them attractive targets for therapeutic intervention. More is being discovered regarding the intricate interplay of mast cells and eosinophils. Recent studies demonstrating that depletion of eosinophils is insufficient to improve symptoms of EGIDs have raised the question of whether other cells may play a role in symptomatology and pathogenesis of EGIDs.

Persistent esophageal changes after histologic remission in eosinophilic esophagitis

BACKGROUND

Eosinophilic esophagitis (EoE) is characterized by persistent or relapsing allergic inflammation, and both clinical and histologic features of esophageal inflammation persist over time in most individuals. Mechanisms contributing to EoE relapse are not understood, and chronic EoE-directed therapy is therefore required to prevent long-term sequelae.

OBJECTIVE

We investigated whether EoE patients in histologic remission have persistent dysregulation of esophageal gene expression.

METHODS

Esophageal biopsy samples from 51 pediatric and 52 adult subjects with EoE in histopathologic remission (<15 eosinophils per high-power field [eos/hpf]) and control (48 pediatric and 167 adult) subjects from multiple institutions were subjected to molecular profiling by the EoE diagnostic panel, which comprises a set of 94 esophageal transcripts differentially expressed in active EoE.

RESULTS

Defining remission as <15 eos/hpf, we identified 51 and 32 differentially expressed genes in pediatric and adult EoE patients compared to control individuals, respectively (false discovery rate < 0.05). Using the stringent definition of remission (0 eos/hpf), the adult and pediatric cohorts continued to have 18 and 25 differentially expressed genes (false discovery rate < 0.05). Among 6 shared genes between adults and children, CDH26 was upregulated in both children and adults; immunohistochemistry demonstrated increased cadherin 26 staining in the epithelium of EoE patients in remission compared to non-EoE controls. In the adult cohort, POSTN expression correlated with the endoscopic reference system score (Spearman r = 0.35, P = .011), specifically correlating with the rings' endoscopic reference system subscore (r = 0.53, P = .004).

CONCLUSION

We have identified persistent EoE-associated esophageal gene expression in patients with disease in deep remission. These data suggest potential inflammation-induced epigenetic mechanisms may influence gene expression during remission in EoE and provide insight into possible mechanisms that underlie relapse in EoE.

Alpha-Tryptase as a Risk-Modifying Factor for Mast Cell-Mediated Reactions

PURPOSE OF REVIEW

To provide an overview on the current understanding of genetic variability in human tryptases and summarize the literature demonstrating the differential impact of mature tryptases on mast cell-mediated reactions and associated clinical phenotypes.

RECENT FINDINGS

It is becoming increasingly recognized that tryptase gene composition, and in particular the common genetic trait hereditary alpha-tryptasemia (HαT), impacts clinical allergy. HαT has consistently been associated with clonal mast cell disorders (MCD) and has also been associated with more frequent anaphylaxis among these patients, and patients in whom no allergic trigger can be found, specifically idiopathic anaphylaxis. Additionally, more severe anaphylaxis among Hymenoptera venom allergy patients has been linked to HαT in both retrospective and prospective studies. An increased relative number of α-tryptase-encoding gene copies, even in the absence of HαT, has also been associated with systemic mastocytosis and has been shown to positively correlate with the severity of mast cell-mediated reactions to vibration and food. These findings may be due to increased generation of α/β-tryptase heterotetramers and differences in their enzymatic activity relative to β-tryptase homotetramers. HαT is a naturally occurring overexpression model of α-tryptase in humans. Increased relative α-tryptase expression modifies immediate hypersensitivity symptoms and is associated with more frequent and severe mast cell-mediated reactions, ostensibly due to increased α/β-tryptase heterotetramer production.

Detecting Changes in Mast Cell Numbers Versus Activation in Human Disease: A Roadblock for Current Biomarkers?

The pathophysiology of mast cell (MC)-driven disorders is diverse, ranging from localized reactions to systemic disorders caused by abnormal accumulation and activation in multiorgan systems. Prompt and accurate diagnosis is critically important, both for informing treatment and objective assessment of treatment outcomes. As new therapeutics are being developed to deplete MCs or silence them (eg, by engaging inhibitory receptors that block activation), new biomarkers are needed that can distinguish between MC activation versus burden. Serum tryptase is the gold standard for assessing both MC burden and activation; however, commercial tryptase assays have limitations related to timing of release, lack of discernment between inactive (α) and active (β) forms of tryptase, and interpatient variability of baseline levels. Alternative approaches to measuring MC activation include urinary MC mediators, flow cytometry-based assays or gene expression profiling. Additional markers of MC activation are needed for use in clinical diagnostics, to help selection of treatment of MC diseases, and for assessing outcomes of therapy. We review the spectrum of disorders with known or suspected MC contribution, describe the utility and limitations of current MC markers and assays, and discuss the need for new markers that can differentiate between MC activation and burden.

Regulatory T cells Are Increased and Correlate With Mast Cells in Eosinophilic Esophagitis

Background/Aims

The incidence of eosinophilic esophagitis (EoE) has been increasing recently. The role of regulatory T cells (Tregs) and correlations with other inflammatory cells in EoE remain unknown. We aim to clarify the role of Tregs and their correlations with inflammatory cells in EoE patients.

Methods

Biopsies from controls and EoE patients before and after treatments were analyzed. Eosinophil infiltration was evaluated by hematoxylin and eosin staining. Immunohistochemical staining was performed to examine infiltration of T cells, Tregs, and mast cells. Gene expressions of chemokines were evaluated by reverse transcription-quantitative polymerase chain reaction.

Results

Tregs and mast cells were increased in the esophageal epithelial layers of EoE patients. After treatments, Tregs and mast cells were decreased when histologic remission was achieved. Infiltration of Tregs correlated significantly with numbers of eosinophils and mast cells. Filaggrin mRNA was decreased in patients with EoE before treatment and upregulated after treatment, even when histologic remission was not achieved.

Conclusions

Tregs were increased in esophageal epithelium of patients with EoE, and correlated with mast cell infiltration.

Reduction of Th2 inflammation and fibrosis in eosinophilic esophagitis in a murine model by citri reticulatae pericarpium

ETHNOPHARMACOLOGICAL RELEVANCE

Inflammation and subepithelial fibrosis play major roles in the early pathology of eosinophilic esophagitis (EoE). However, there are currently no pharmacotherapeutic interventions that directly target eosinophilic esophagitis. Citri Reticulatae Pericarpium (CRP, known as Chen-Pi) is one of most frequently used qi-regulating drugs in Chinese medicine and nutrition. CRP is rich with flavonones and polymethoxy flavones, both of which exhibit superior anti-inflammatory, anti-allergic and anti-fibrosis effects. This study is to investigate intervention effect of CRP on EoE, to identify its active compounds and to explore its underlying mechanisms.

METHODS

The CRP extract was obtained by liquid-liquid extraction with 70% ethanol, and its main components were identified by HPLC and TLC chromatography as hesperidin, nobiletin, tangeretin, and narirutin in turn. Furthermore, we evaluated its effect and underlying mechanisms in an PN (Peanut protein extract)-sensitized murine model of food allergy induced EoE.

RESULTS

CRP treatment attenuated EoE model mice symptomatology, blocked hypothermia, reduced the production of PN-specific IgE and IgG1 and TH2 cytokines (interleukin (IL)-4 and IL-5), and increased the level of anti-inflammatory cytokines IL-10 and interferon (IFN)-γ. CRP treatment also significantly alleviated the pathological damage and reduced fibrosis in inflamed tissues like esophagus, lung, and intestine. These results were strongly associated with reducing the expression of p-p38 mitogen-activated protein kinase (MAPK), transforming growth factor beta1 (TGF-β1) and p-Smad 3 proteins.

CONCLUSION

CRP extract markedly inhibited TH2 immune response and attenuated subepithelial fibrosis with a dose-dependent manner through down-regulating MAPK/TGF-β signaling pathway. It is suggested that CRP extract might serve as a potential therapy for food allergy-induced EoE like disease.

Mast Cell Disorders of the Gastrointestinal Tract: Clarity out of Chaos

Pathologists are increasingly asked to evaluate mast cell infiltrates in the gastrointestinal tract when there is clinical concern for systemic mastocytosis or a variety of functional disorders, including irritable bowel syndrome and mast cell activation syndrome. Neoplastic mast cells have established quantitative, morphologic, and immunohistochemical features that facilitate their identification in gastrointestinal mucosal biopsies. Specific qualitative and quantitative findings are lacking for inflammatory mast cell-mediated disorders. This review covers histopathologic features of mast cell disorders that affect the gastrointestinal tract and offers practical guidance for their assessment in mucosal biopsies.

Assessment of the Severity and the Remission Criteria in Eosinophilic Esophagitis

Eosinophilic esophagitis (EoE) is an immune-mediated disease that manifests with dysphagia and is characterized by the predominantly eosinophilic infiltration of the esophageal mucosa. Several instruments have been developed to assess the symptoms of EoE: the Daily Symptom Questionnaire (DSQ), EoE Activity Index (EEsAI), Pediatric EoE Symptom Severity (PEESSv2), etc. The use of the EREFS is a gold standard for endoscopic diagnosis. The EoE histologic scoring system (EoEHSS) was elaborated for the assessment of histological features in EoE. However, the remission criteria are not clearly defined and vary greatly in different studies. Gastroenterologists establish the severity of EoE mainly based on endoscopic findings. At the same time, EoE requires a multidisciplinary approach. The recently developed Index of Severity of Eosinophilic Esophagitis (I-SEE) that is built on symptoms, endoscopic findings, and histological features is promising.

Machine Learning Based Identification and Characterization of Mast cells in Eosinophilic Esophagitis

Background

Eosinophilic esophagitis (EoE) is diagnosed and monitored using esophageal eosinophil levels; however, EoE also exhibits a marked, understudied esophageal mastocytosis.

Objective

Using machine learning, we localized and characterized esophageal mast cells to decipher their potential role in disease pathology.

Methods

Esophageal biopsy samples (EoE, control) were stained for mast cells by anti-tryptase and imaged using immunofluorescence; high-resolution whole tissue images were digitally assembled. Machine learning software was trained to identify, enumerate, and characterize mast cells, designated Mast Cell-Artificial Intelligence (MC-AI).

Results

MC-AI enumerated cell counts with high accuracy. During active EoE, epithelial mast cells increased and lamina propria (LP) mast cells decreased. In controls and EoE remission patients, papillae had the highest mast cell density and negatively correlated with epithelial mast cell density. Mast cell density in the epithelium and papillae correlated with the degree of epithelial eosinophilic inflammation, basal zone hyperplasia, and LP fibrosis. MC-AI detected greater mast cell degranulation in the epithelium, papillae, and LP in EoE patients compared with control individuals. Mast cells were localized further from the basement membrane in active EoE than EoE remission and controls individuals but were closer than eosinophils to the basement membrane in active EoE.

Conclusion

Using MC-AI, we identified a distinct population of homeostatic esophageal papillae mast cells; during active EoE, this population decreases, undergoes degranulation, negatively correlates with epithelial mast cell levels, and significantly correlates with distinct histologic features. Overall, MC-AI provides a means to understand the potential involvement of mast cells in EoE and other disorders.

Clinical Implication

We have developed a methodology for identifying, enumerating, and characterizing mast cells using artificial intelligence; this has been applied to decipher eosinophilic esophagitis and provides a platform approach for other diseases.

Capsule Summary

A machine learning protocol for identifying mast cells, designated Mast Cell-Artificial Intelligence, readily identified spatially distinct and dynamic populations of mast cells in EoE, providing a platform to better understand this cell type in EoE and other diseases.

Mast cells disrupt the function of the esophageal epithelial barrier

Mast cells (MCs) accumulate in the epithelium of patients with eosinophilic esophagitis (EoE), an inflammatory disorder characterized by extensive esophageal eosinophilic infiltration. Esophageal barrier dysfunction plays an important role in the pathophysiology of EoE. We hypothesized that MCs contribute to the observed impaired esophageal epithelial barrier. Herein, we demonstrate that coculture of differentiated esophageal epithelial cells with immunoglobulin E-activated MCs significanly decreased epithelial resistance by 30% and increased permeability by 22% compared with non-activated MCs. These changes were associated with decreased messenger RNA expression of barrier proteins filaggrin, desmoglein-1 and involucrin, and antiprotease serine peptidase inhibitor kazal type 7. Using targeted proteomics, we detected various cytokines in coculture supernatants, most notably granulocyte-macrophage colony-stimulating factor and oncostatin M (OSM). OSM expression was increased by 12-fold in active EoE and associated with MC marker genes. Furthermore, OSM receptor-expressing esophageal epithelial cells were found in the esophageal tissue of patients with EoE, suggesting that the epithelial cells may respond to OSM. Stimulation of esophageal epithelial cells with OSM resulted in a dose-dependent decrease in barrier function and expression of filaggrin and desmoglein-1 and an increase in protease calpain-14. Taken together, these data suggest a role for MCs in decreasing esophageal epithelial barrier function in EoE, which may in part be mediated by OSM.

Stem cell factor inhibition reduces Th2 inflammation and cellular infiltration in a mouse model of eosinophilic esophagitis

Eosinophilic esophagitis (EoE) is a T helper (Th)2-mediated inflammatory disorder characterized endoscopically by eosinophilic infiltration leading to fibrosis of the esophagus. Stem cell factor (SCF), a multifunctional cytokine, is upregulated in several allergic diseases, including in patients with EoE. Mast cells and eosinophils express c-kit, the cell surface receptor for SCF, and have been found to play an important role in EoE. Therefore, we investigated whether blocking SCF represents a potential therapeutic approach for EoE. Esophageal inflammation was induced in mice using peanut allergen. In mice with experimental EoE, we found that SCF was upregulated in the esophageal tissue. In EoE mice injected with a polyclonal antibody specific for SCF, we observed a decrease in both mast cells and eosinophils by histological and flow cytometric analysis. Furthermore, Th2 cytokines in the esophagus were decreased in anti-SCF treated mice, as were levels of Th2 cytokines from lung-draining and esophageal lymph nodes. Serum levels of peanut-specific immunoglobulin E were reduced following treatment with anti-SCF. In Kitlf/f-Col1-Cre-ERT mice, which have SCF deleted primarily in myofibroblasts that develop in EoE, we observed similar results as the anti-SCF treated animals for inflammatory cell accumulation, cytokines, and histopathology. These results indicate that therapeutic treatments targeting SCF can reduce allergic inflammation in EoE.

Eosinophilic Esophagitis Histologic Scoring System: Correlation with Histologic, Endoscopic, and Symptomatic Disease and Clinical Use

BACKGROUND

The eosinophilic esophagitis histologic scoring system (EoEHSS) was developed to enhance the diagnostic standard of peak eosinophil count (PEC) in evaluating disease activity in EoE.

AIMS

(1) Correlate the EoEHSS and PEC to measures of symptomatic and endoscopic disease activity, (2) Correlate EoEHSS grade and stage subcomponents to clinical, radiology, and endoscopic markers of fibrotic disease, (3) Evaluate EoEHSS remission in asymptomatic patients with PEC < 15 eosinophils per high powered field (eos/hpf).

METHODS

Secondary analysis of prospective cohort data of 22 patients with EoE that underwent dietary therapy and endoscopy at 3 time points. Active disease was defined by EoEHSS grade or stage > 0.125, symptomatic disease by EoE symptom activity index > 20, endoscopic disease by endoscopic reference score > 2, and histologic disease by PEC ≥ 15 eos/hpf. EoEHSS remission was defined by esophageal inflammation (EI) grade of 0-1, EI stage of 0, total grade ≤ 3, and total stage ≤ 3.

RESULTS

EoEHSS grade and stage did not correlate with symptomatic disease but did with endoscopic and histologic disease. PEC showed similar correlation pattern. Abnormal grade and stage had strong sensitivity (87-100%) but poor specificity (11-36%) to detect symptomatic, endoscopic, and histologic disease activity. Lamina propria fibrosis was evaluated in 36% of biopsies and did not correlate with minimum esophageal diameter. Out of 14 patients who were in complete symptomatic, endoscopic, and histologic remission, 8 met criteria for EoEHSS remission.

CONCLUSION

The positive and negative correlations of EoEHSS to specific measures of symptomatic, histologic, and endoscopic activity suggest that it provides complementary information in EoE.

Esophageal mast cells may be associated with the perception of symptoms in patients with eosinophilic esophagitis

BACKGROUND

Eosinophilic esophagitis (EoE) is a type 2 helper T-cell (Th2)-mediated allergic disease that involves mast cells. This study aimed to clarify the relationship between perception of symptoms and mast cell levels in patients with EoE.

METHODS

We enrolled patients with asymptomatic esophageal eosinophilia (aEE) and those with symptomatic EoE. Immunofluorescence staining was performed on esophageal biopsy specimens to quantify mast cell-related molecules, such as tryptase, proteinase-activated receptor (PAR)-2, and vasoactive intestinal peptide receptor (VPAC)-1.

RESULTS

We evaluated 28 and 58 patients with aEE and EoE, respectively. There were no significant differences in clinical and endoscopic features and peak eosinophil counts between both groups. Mast cell tryptase-positive areas were significantly higher in EoE than in aEE (4.9 [3.5-6.2] vs. 2.0 [1.2-3.4] %, p < 0.01). The number of PAR-2-positive cells was significantly higher in EoE than in aEE (14 [8.8-20.0] vs. 4 [2.8-8.0] cells/high-power field [HPF], p < 0.01). The number of VPAC-1-positive cells was significantly higher in the EoE group than in the aEE group (13 [8.8-16.0] vs. 6 [3.0-9.3] cells/HPF, p < 0.01). A positive correlation was observed between the numbers of PAR-2-positive cells and VPAC-1-positive cells (r = 0.851, p < 0.01). Moreover, mast cell tryptase-positive areas positively correlated with the number of PAR-2- and VPAC-1-positive cells (r = 0.352, p < 0.01; r = 0.355, p < 0.01, respectively).

CONCLUSIONS

Esophageal mast cells and their receptors, PAR-2 and VPAC-1, may contribute to the perception of symptoms in patients with EoE.

What Is the Value of Counting Mast Cells in Gastrointestinal Mucosal Biopsies?

Neoplastic and nonneoplastic mast cell disorders can cause diarrhea, nausea, and abdominal pain that result from heightened release of mast cell mediators. Systemic mastocytosis is characterized by neoplastic mast cell aggregates in the bone marrow and other sites, particularly the skin and gastrointestinal tract. In this situation, extramedullary mast cell aggregates display atypical morphology, with aberrant immunostaining for CD25 in addition to staining for other mast cell markers, such as mast cell tryptase and CD117. Morphologically normal mast cells have also been implicated in nonneoplastic conditions. For example, increased mast cell numbers have been reported in the mucosal biopsy samples from patients with irritable bowel syndrome and hereditary alpha-tryptasemia. Patients with mast cell activation syndrome presumably experience symptoms related to the aberrant elaboration of histamine and other mediators from normal-appearing mast cells present in normal numbers. Unfortunately, similarities in terminology among these biologically distinct clinical conditions have caused considerable diagnostic confusion among clinical colleagues, resulting in frequent requests for pathologists to quantify and characterize mast cells in normal gastrointestinal biopsy samples from patients with diarrheal symptoms. The purpose of this review is to summarize the available data related to mast cell assessment in the gastrointestinal tract and provide pathologists with practical information so that they can help their clinical colleagues manage patients with presumed mast cell disorders.

Epithelial-intrinsic defects in TGFβR signaling drive local allergic inflammation manifesting as eosinophilic esophagitis

Allergic diseases are a global health challenge. Individuals harboring loss-of-function variants in transforming growth factor-β receptor (TGFβR) genes have an increased prevalence of allergic disorders, including eosinophilic esophagitis. Allergic diseases typically localize to mucosal barriers, implicating epithelial dysfunction as a cardinal feature of allergic disease. Here, we describe an essential role for TGFβ in the control of tissue-specific immune homeostasis that provides mechanistic insight into these clinical associations. Mice expressing a TGFβR1 loss-of-function variant identified in atopic patients spontaneously develop disease that clinically, immunologically, histologically, and transcriptionally recapitulates eosinophilic esophagitis. In vivo and in vitro, TGFβR1 variant-expressing epithelial cells are hyperproliferative, fail to differentiate properly, and overexpress innate proinflammatory mediators, which persist in the absence of lymphocytes or external allergens. Together, our results support the concept that TGFβ plays a fundamental, nonredundant, epithelial cell-intrinsic role in controlling tissue-specific allergic inflammation that is independent of its role in adaptive immunity.

Mast cells in food allergy: Inducing immediate reactions and shaping long-term immunity

Mast cells are distributed throughout the gastrointestinal tract and function as the main effector cells of IgE-mediated allergic reactions to foods. Allergen-induced cross-linking of IgE antibodies bound to high-affinity IgE receptors, FcεRI, on the surface of mast cells triggers their activation, resulting in the release of mediators of immediate hypersensitivity. These mediators rapidly induce both local gastrointestinal and systemic physiological responses including anaphylaxis. Emerging evidence has revealed that, in addition to inciting immediate reactions, mast cells are key regulators of adaptive immunity to foods. In the gastrointestinal mucosa they provide the priming cytokines that initiate and, over time, consolidate adaptive T_H2 responses to ingested allergens as well as TNF and chemokines that orchestrate the recruitment of tissue-infiltrating leukocytes that drive type 2 tissue inflammation. Patients with atopic dermatitis have increased intestinal mast cell numbers and are at a greater risk for food allergy. Recent studies have uncovered a skin-gut axis in which epicutaneous allergen exposure drives intestinal mast cell expansion. The activating effects of IgE antibodies in mast cells are countered by food-specific IgG antibodies that signal via the inhibitory IgG receptor, FcγR2b, suppressing both immediate allergic reactions to foods and the type 2 immune adjuvant activity of mast cells.

Breaking down the complex pathophysiology of eosinophilic esophagitis

Eosinophilic esophagitis (EoE) is a chronic and progressive immune-mediated disease of the esophagus associated with antigen-driven type 2 inflammation and symptoms of esophageal dysfunction. Our understanding of EoE pathophysiology has evolved since its initial recognition more than 20 years ago and has translated into diagnostic and novel therapeutic approaches that are affecting patient care. The mechanisms underlying disease development and progression are influenced by diverse factors, such as genetics, age, allergic comorbidities, and allergen exposures. Central to EoE pathophysiology is a dysregulated feed-forward cycle that develops between the esophageal epithelium and the immune system. Allergen-induced, type 2-biased immune activation by the esophageal epithelium propagates a cycle of impaired mucosal barrier integrity and allergic inflammation, eventually leading to tissue remodeling and progressive organ dysfunction. Herein, we review the current understanding of fundamental pathophysiological mechanisms contributing to EoE pathogenesis.

Role of mast cells in eosinophilic esophagitis

PURPOSE OF REVIEW

This review will present what is known from recent research on the involvement of mast cells in eosinophilic esophagitis and identify questions requiring further investigation.

RECENT FINDINGS

In the adults and children with eosinophilic esophagitis, there is increasing evidence that mastocytosis can persist, despite resolution of eosinophilia and is associated with persistent mucosal abnormalities and symptoms. Despite, treatment mast cells have an activated transcriptome. Mast cells likely contribute to epithelial barrier dysfunction, smooth muscle hypertrophy and contraction, and subepithelial fibrosis. It remains unclear whether targeting MCs alone has therapeutic efficacy to improve tissue damage.

SUMMARY

Mast cells appear to play a key role in eosinophilic esophagitis and serve as a biomarker of mucosal healing in conjunction with eosinophils. Excessive mast cell activation likely contributes to tissue damage in eosinophilic esophagitis and need to be considered as a target of therapy along with eosinophils.

Eosinophilic esophagitis: Immune mechanisms and therapeutic targets

Eosinophilic esophagitis (EoE) is an emerging chronic inflammatory disease of the oesophagus and is clinically characterized by upper gastrointestinal (GI) symptoms including dysphagia and esophageal food impaction. Histopathologic manifestations, which include intraepithelial eosinophilic inflammation and alterations of the esophageal squamous epithelium, such as basal zone hyperplasia (BZH) and dilated intercellular spaces (DIS), are thought to contribute to esophageal dysfunction and disease symptoms. Corroborative clinical and discovery science-based studies have established that EoE is characterized by an underlying allergic inflammatory response, in part, related to the IL-13/CCL26/eosinophil axis driving dysregulation of several key epithelial barrier and proliferative regulatory genes including kallikrein (KLK) serine proteases, calpain 14 (CAPN14) and anoctamin 1 (ANO1). The contribution of these inflammatory and proliferative processes to the clinical and histological manifestations of disease are not fully elucidated. Herein, we discuss the immune molecules and cells that are thought to underlie the clinical and pathologic manifestations of EoE and the emerging therapeutics targeting these processes for the treatment of EoE.

Esophageal Mucosal Permeability as a Surrogate Measure of Cure in Eosinophilic Esophagitis

This study aimed to evaluate the relationship of esophageal epithelial permeability with mast cell infiltration and IgG4 deposits as well as chemokine levels in eosinophilic esophagitis (EoE) patients before and after treatment. Biopsies from controls and EoE patients before and after treatment were analyzed. Hematoxylin and eosin staining was used to show eosinophil infiltration. Paracellular permeability of the esophageal epithelium was assessed using surface biotinylation. Immunohistochemical staining was performed to examine mast cell infiltration and IgG4 deposits. Gene expression of chemokines was evaluated by qRT-PCR. Esophageal epithelial infiltration of mast cells, IgG4 deposits, and permeability were significantly increased in EoE patients. Levels of interleukin-13, calpain-14, and eotaxin-3 mRNAs were significantly upregulated, while filaggrin, serine peptidase inhibitor Kazal type 7 (SPINK7), and involucrin mRNAs were significantly downregulated in EoE patients. In patients achieving histologic remission diagnosed by eosinophil counts, a subset of EoE patients with unchanged permeability after treatment showed increases in mast cell infiltration, IgG4 deposits, and interleukin-13, calpain-14, filaggrin, and SPINK7 expression, with decreased eotaxin-3 and involucrin. Other EoE patients with decreased permeability displayed decreased eotaxin-3, involucrin, and mast cell infiltration, no IgG4 deposits, and increased IL-13, calpain-14, filaggrin, and SPINK7. Increased permeability of the esophagus in EoE patients without eosinophil infiltration after treatment was associated with mast cell infiltration and IgG4 deposits.

A Clinical Severity Index for Eosinophilic Esophagitis: Development, Consensus, and Future Directions

BACKGROUND & AIMS

Disease activity and severity of eosinophilic esophagitis (EoE) dictate therapeutic options and management, but the decision-making process for determining severity varies among practitioners. To reduce variability in practice patterns and help clinicians monitor the clinical course of the disease in an office setting, we aimed to create an international consensus severity scoring index for EoE.

METHODS

A multidisciplinary international group of adult and pediatric EoE researchers and clinicians, as well as non-EoE allergy immunology and gastroenterology experts, formed 3 teams to review the existing literature on histology, endoscopy, and symptoms of EoE in the context of progression and severity. A steering committee convened a 1-day virtual meeting to reach consensus on each team's opinion on salient features of severity across key clinicopathologic domains and distill features that would allow providers to categorize disease severity.

RESULTS

Symptom features and complications and inflammatory and fibrostenotic features on both endoscopic and histologic examination were collated into a simplified scoring system-the Index of Severity for Eosinophilic Esophagitis (I-SEE)-that can be completed at routine clinic visits to assess disease severity using a point scale of 0-6 for mild, 7-14 for moderate, and ≥15 for severe EoE.

CONCLUSIONS

A multidisciplinary team of experts iteratively created a clinically usable EoE severity scoring system denominated "I-SEE" to guide practitioners in EoE management by standardizing disease components reflecting disease severity beyond eosinophil counts. I-SEE should be validated and refined using data from future clinical trials and routine clinical practice to increase its utilization and functionality.

A Clinical Severity Index for Eosinophilic Esophagitis: Development, Consensus, and Future Directions

BACKGROUND & AIMS

Disease activity and severity of eosinophilic esophagitis (EoE) dictate therapeutic options and management, but the decision-making process for determining severity varies among practitioners. To reduce variability in practice patterns and help clinicians monitor the clinical course of the disease in an office setting, we aimed to create an international consensus severity scoring index for EoE.

METHODS

A multidisciplinary international group of adult and pediatric EoE researchers and clinicians, as well as non-EoE allergy immunology and gastroenterology experts, formed 3 teams to review the existing literature on histology, endoscopy, and symptoms of EoE in the context of progression and severity. A steering committee convened a 1-day virtual meeting to reach consensus on each team's opinion on salient features of severity across key clinicopathologic domains and distill features that would allow providers to categorize disease severity.

RESULTS

Symptom features and complications and inflammatory and fibrostenotic features on both endoscopic and histologic examination were collated into a simplified scoring system-the Index of Severity for Eosinophilic Esophagitis (I-SEE)-that can be completed at routine clinic visits to assess disease severity using a point scale of 0-6 for mild, 7-14 for moderate, and ≥15 for severe EoE.

CONCLUSIONS

A multidisciplinary team of experts iteratively created a clinically usable EoE severity scoring system denominated "I-SEE" to guide practitioners in EoE management by standardizing disease components reflecting disease severity beyond eosinophil counts. I-SEE should be validated and refined using data from future clinical trials and routine clinical practice to increase its utilization and functionality.

Single-cell RNA sequencing of mast cells in eosinophilic esophagitis reveals heterogeneity, local proliferation, and activation that persists in remission

BACKGROUND

Mast cells (MCs) are pleiotropic cells that accumulate in the esophagus of patients with eosinophilic esophagitis (EoE) and are thought to contribute to disease pathogenesis, yet their properties and functions in this organ are largely unknown.

OBJECTIVES

This study aimed to perform a comprehensive molecular and spatial characterization of esophageal MCs in EoE.

METHODS

Esophageal biopsies obtained from patients with active EoE, patients with EoE in histologic remission, and individuals with histologically normal esophageal biopsies and no history of esophageal disease (ie, control individuals) were subject to single-cell RNA sequencing, flow cytometry, and immunofluorescence analyses.

RESULTS

This study probed 39,562 single esophageal cells by single-cell RNA sequencing; approximately 5% of these cells were MCs. Dynamic MC expansion was identified across disease states. During homeostasis, TPSAB1^highAREG^high resident MCs were mainly detected in the lamina propria and exhibited a quiescent phenotype. In patients with active EoE, resident MCs assumed an activated phenotype, and 2 additional proinflammatory MC populations emerged in the intraepithelial compartment, each linked to a proliferating MKI67^high cluster. One proinflammatory activated MC population, marked as KIT^highIL1RL1^highFCER1A^low, was not detected in disease remission (termed "transient MC"), whereas the other population, marked as CMA1^highCTSG^high, was detected in disease remission where it maintained an activated state (termed "persistent MC"). MCs were prominent producers of esophageal IL-13 mRNA and protein, a key therapeutic target in EoE.

CONCLUSIONS

Esophageal MCs comprise heterogeneous populations with transcriptional signatures associated with distinct spatial compartmentalization and EoE disease status. In active EoE, they assume a proinflammatory state and locally proliferate, and they remain activated and poised to reinitiate inflammation even during disease remission.

Benralizumab Completely Depletes Gastrointestinal Tissue Eosinophils and Improves Symptoms in Eosinophilic Gastrointestinal Disease

BACKGROUND

Previous studies of targeted eosinophil biologics in eosinophilic esophagitis have yielded mixed results. Possible explanations include incomplete eosinophil depletion with anticytokine (anti-IL-5) treatments and/or irreversible fibrotic tissue changes contributing to symptomatology.

OBJECTIVE

To characterize the therapeutic effect of eosinophil depletion in patients with hypereosinophilic syndrome with varied eosinophilic gastrointestinal (GI) disorders.

METHODS

Hematologic, histologic, endoscopic, and clinical symptoms for a subset (n = 7) of hypereosinophilic syndrome patients with GI tissue eosinophilia enrolled in a phase 2 clinical trial of benralizumab (anti-IL-5RA) were assessed before and after treatment (NCT02130882).

RESULTS

Blood and GI tissue eosinophils were completely depleted in all segments of the GI tract, and all patients reported improved GI symptoms, in some cases as early as after the first monthly dose. Some patients had recurrent symptomatic flares without recurrent peripheral or tissue eosinophilia, in most cases after prolonged symptomatic remission and in the setting of liberalization of dietary restrictions and/or tapering of background therapy. Although eosinophil-associated histologic changes improved in all segments, epithelial changes persisted in the esophagus and stomach in patients with recurrent disease flares even after 1 year of treatment. Serum tryptase and GI mast cells were generally unchanged with treatment, and increases were not associated with disease flares. Serum levels of IL-4 and IL-5 increased with benralizumab treatment (both P < .05).

CONCLUSIONS

Benralizumab treatment completely depleted blood and GI tissue eosinophilia in patients with eosinophilic GI disorders, but clinical response, while encouraging, was heterogeneous. Residual symptoms in some patients may reflect persistent epithelial changes in the upper GI tract.

Eosinophilic Esophagitis Symptom Scores Are High in Children Without Eosinophilic Disease

OBJECTIVES

The Pediatric Eosinophilic Esophagitis (EoE) Symptom Score version 2 (PEESSv2.0) is an EoE-specific validated metric for disease monitoring, but its use has not been explored outside of EoE. Our aim was to determine if PEESSv2.0 scores differentiate between children with EoE and non-EoE esophageal dysfunction undergoing initial esophagogastroduodenoscopy (EGD).

METHODS

A prospective cohort study of pediatric subjects was conducted. Children ages 1-18 undergoing initial EGD for esophageal dysfunction were enrolled. Demographics, clinical history, and child self-report and parent-proxy report PEESSv2.0 symptom scores were collected at the time of EGD. Esophageal biopsies were reviewed, and EoE was defined as >15 eosinophils/high powered field (hpf) seen in any level of the esophagus. Non-EoE was defined as <15 eosinophils/hpf.

RESULTS

Seventy-one children were included in the study from 2015 to 2018 [59% (42/71) males; mean age 9.2 years; range 1-17 years]. Fifty-eight percent (41/71) met criteria for EoE, and 42% (30/71) were labeled non-EoE. Non-EoE children and their parents had higher/worse median PEESSv2.0 total scores than those with EoE [47.0 vs 28.0 (P = 0.001) and 40.5 vs 26.5 (P = 0.012), respectively]. Non-EoE children reported higher median GERD [9.0 vs 4.0 (P = 0.003)], nausea/vomiting [9.0 vs 4.0 (P = 0.003)], and pain [11.0 vs 6.0 (P = 0.001)] subdomain scores compared to those with EoE. PEESSv2.0 dysphagia subdomain scores (child and parent-proxy) did not differ between EoE and non-EoE groups [22.0 vs 15.0 (P = 0.184) and 18.5 vs 17.4 (P = 0.330), respectively].

DISCUSSION

Total PEESSv2.0 scores were worse in non-EoE group compared to EoE group. Although PEESSv2.0 is validated for use in monitoring EoE therapy, it does not distinguish children with EoE from non-EoE esophageal dysfunction at the time of diagnostic EGD.

Determination of Biopsy Yield That Optimally Detects Eosinophilic Gastritis and/or Duodenitis in a Randomized Trial of Lirentelimab

BACKGROUND & AIMS

Eosinophilic gastritis (EG) and eosinophilic duodenitis (EoD), characterized by chronic gastrointestinal (GI) symptoms and increased numbers or activation of eosinophils and mast cells in the GI tract, are likely underdiagnosed. We aimed to determine rates of EG and EoD and number of biopsies required to optimize detection using screening data from a randomized trial of lirentelimab (AK002), an antibody against siglec-8 that depletes eosinophils and inhibits mast cells. We also characterized endoscopic features and symptoms of EG and EoD.

METHODS

Subjects with moderate-to-severe GI symptoms, assessed daily through a validated patient-reported outcome questionnaire, underwent endoscopy with a systematic gastric and duodenal biopsy protocol and histopathologic evaluation. EG diagnosis required presence of ≥30 eosinophils/high-power field (eos/hpf) in ≥5 hpfs and EoD required ≥30 eos/hpf in ≥3 hpfs. We analyzed diagnostic yields for EG and EoD and histologic, endoscopic, and clinical findings.

RESULTS

Of 88 subjects meeting symptom criteria, 72 were found to have EG and/or EoD (EG/EoD), including patients with no prior diagnosis of EG/EoD. We found that GI eosinophilia was patchy and that examination of multiple biopsies was required for diagnosis-an average of only 2.6 per 8 gastric biopsies and 2.2 per 4 duodenal biopsies per subject met thresholds for EG/EoD. Evaluation of multiple nonoverlapping hpfs in each of 8 gastric and 4 duodenal biopsies was required to capture 100% of EG/EoD cases. Neither endoscopic findings nor symptom severity correlated with eosinophil counts.

CONCLUSIONS

In an analysis of patients with moderate-to-severe GI symptoms participating in a clinical trial of lirentelimab for EG/EoD, we found eosinophilia to be patchy in gastric and duodenal biopsies. Counting eosinophils in at least 8 gastric and 4 duodenal biopsies is required to identify patients with EG/EoD, so they can receive appropriate treatment. (ClinicalTrials.gov, Number: NCT03496571).

Proton Pump Inhibitor Therapy for Eosinophilic Esophagitis: History, Mechanisms, Efficacy, and Future Directions

Over the past decade, the role of proton pump inhibitor (PPI) medication has evolved from a diagnostic tool for Eosinophilic Esophagitis (EoE), by excluding patients with PPI responsive esophageal eosinophilia (PPI-REE), to a therapy for EoE. This transition resulted from the Updated International Consensus Diagnostic Criteria for Eosinophilic Esophagitis: Proceedings of the Appraisal of Guidelines for Research and Evaluation II (AGREE) Conference to support PPI therapy for EoE in children and adults. Additional recent advances have suggested a role for genetic variations that might impact response to PPI therapy for EoE. This review article will explore a brief background of EoE, the evolution of PPI therapy for EoE and its proposed mechanisms, efficacy and safety in children and adults, and considerations for future PPI precision medicine in patients with EoE.

Responsiveness of a Histologic Scoring System Compared With Peak Eosinophil Count in Eosinophilic Esophagitis

INTRODUCTION

The optimal instrument for assessing histologic disease activity in patients with eosinophilic esophagitis (EoE) is unclear. We assessed the responsiveness of the EoE Histologic Scoring System (EoE-HSS) when compared with that of the peak eosinophil count (PEC).

METHODS

Histopathology slides were obtained from patients with EoE at baseline and after 8 weeks of treatment with swallowed topical budesonide or elimination diet. Two blinded gastrointestinal pathologists scored biopsies on the EoE-HSS, PEC, and 100-mm visual analog scale (VAS) of overall histologic severity. Change was defined as an improvement by ≥0.5 SD in baseline VAS. Responsiveness was quantified using the standardized effect size (SES) and the probability that the index distinguishes a patient with improvement from a patient without improvement, which is the area under the receiver operating characteristic curve (AUC). Longitudinal validity was assessed using Pearson correlations between changes in EoE-HSS and both PEC and VAS.

RESULTS

The EoE-HSS grade (SES 2.18 [95% confidence interval, CI: 1.46-2.88]; AUC 0.73 [95% CI: 0.57-0.84]) and stage (SES 2.07 [95% CI: 1.37-2.77]; AUC 0.73 [95% CI: 0.58-0.84]) were highly responsive, similar to PEC (SES 1.44 [95% CI: 0.80-2.07]; AUC 0.73 [95% CI: 0.58-0.84]). The EoE-HSS grade and stage were more highly correlated with changes in VAS (grade 0.92 [95% CI: 0.86-0.95]; stage 0.89 [95% CI: 0.81-0.94]) than with changes in PEC (grade 0.74 [95% CI: 0.58-0.85]; stage 0.66 [95% CI: 0.47-0.80]).

DISCUSSION

The EoE-HSS is highly responsive, performs similarly to PEC, and is better correlated with changes in overall histologic activity in patients with EoE.

Continued Basal Zone Expansion After Resolution of Eosinophilia in a Child With Eosinophilic Esophagitis on Benralizumab

ABSTRACT

A 20-year-old woman presented with dysphagia at 8 years of age. She underwent esophagogastroduodenoscopy with biopsies (EGD), which was diagnostic of eosinophilic esophagitis. Diet elimination resulted in improvement in symptoms, reduction in eosinophilia, and resolution of basal zone hyperplasia (BZH) on repeat EGD; however, food reintroduction resulted in recurrence of eosinophilia. Subsequently, her pulmonologist started benralizumab, a monoclonal antibody against the interleukin-5 receptor (IL5Rα) on eosinophils, for her asthma. Seven months after starting benralizumab, she underwent EGD for persistent dysphagia, which was notable for resolution of esophageal eosinophilia but demonstrated marked BZH in association with high numbers of CD3+ T cells and tryptase+ mast cells. She transitioned to dupilumab and had resolution of dysphagia. EGD was performed 10 months after starting dupilumab and demonstrated resolution of BZH and mast cell inflammation with significant reduction in T cells. Review of other patients at our center treated with biologics, most commonly dupliumab, reveals varying degrees of BZH in association with mostly CD3+ lymphocyte inflammation. Mast cells and T cells appear to be capable of coordinating mucosal inflammation and symptoms of EoE independent of eosinophilia in a subset of patients.

Type 2 Inflammation in Eosinophilic Esophagitis: From Pathophysiology to Therapeutic Targets

Eosinophilic esophagitis (EoE) is a chronic immune-mediated disease of the esophagus characterized clinically by symptoms related to esophageal dysfunction and histologically by eosinophil-predominant inflammation, whose incidence is rising. It significantly affects patients’ quality of life and, if left untreated, results in fibrotic complications. Although broad consensus has been achieved on first-line therapy, a subset of patients remains non-responder to standard therapy. The pathogenesis of EoE is multifactorial and results from the complex, still mostly undefined, interaction between genetics and intrinsic factors, environment, and antigenic stimuli. A deep understanding of the pathophysiology of this disease is pivotal for the development of new therapies. This review provides a comprehensive description of the pathophysiology of EoE, starting from major pathogenic mechanisms (genetics, type 2 inflammation, epithelial barrier dysfunction, gastroesophageal reflux, allergens, infections and microbiota) and subsequently focusing on the single protagonists of type 2 inflammation (involved cells, cytokines, soluble effectors, surface proteins and transcription factors) that could represent present and future therapeutic targets, while summarizing previous therapeutic approaches in literature.

Critical diagnoses in paediatric gastrointestinal diseases

Gastrointestinal biopsies represent an increasing proportion of the paediatric pathologist's workload, an increase fundamentally due to an expansion of the understanding of the basic clinical, molecular, genetic, and histopathological features of paediatric gastrointestinal disorders. The histological interpretation of endoscopically retrieved gastrointestinal biopsies in children requires a unique set of diagnostic expertise and detailed knowledge of various gastrointestinal disorders that have a predilection for the paediatric population. This article's major role is to highlight the unique problems inherent to paediatric gastrointestinal disorders that require immediate communication with the paediatric surgeon or the gastroenterologist. For this, we tried to cover the most important diseases that a paediatric pathologist might encounter in daily practice. Some of these diseases are relatively rare, such as microvillous inclusion disease and tufting enteropathy, but some are more common such as eosinophilic disorders and inflammatory bowel disease. Awareness of the histopathological features of these diseases, particularly those that are relatively uncommon, is crucial to spare the patient a lengthy and costly evaluation. We made a particular effort to abundantly reference this article should the reader wish to expand on the content of any section.

Mucosal Mast Cell Distribution in the Gastrointestinal Tract of Children: A Preliminary Study for Establishing Reference Values

OBJECTIVES

The physiological number and distribution of mast cells (MCs) in the pediatric gastrointestinal (GI) tract is not well defined and reference values of normality are missing. To define a physiological and disease defining cut-off, a systematic histological exploration of MC distribution from the esophagus to the rectum in healthy as well as in patients with gastrointestinal food allergies (GFA) was performed.

METHODS

Nine pediatric subjects that exhibited unremarkable histopathological evaluations or underwent endoscopy for surveillance reasons after a previous polypectomy of single colonic juvenile polyps served as reference cohort. In all of these subjects, a chronic inflammatory disease (eg, inflammatory bowel disease, celiac disease) or allergy was excluded. In addition, a group of 15 patients with gastrointestinal complaints suspected to be caused by a GFA were investigated. Immunohistochemistry was performed from all biopsies using CD117 (c-Kit) as a reliable marker to identify MCs in the lamina propria.

RESULTS

There were distinct differences of MC counts in all parts of the pediatric GI tract. The highest counts of MCs in both symptomatic patients and control cohort, were found in the duodenum, terminal ileum, cecum and ascending colon. The lowest counts were found in the esophagus. Significant disparities between GFA and healthy subjects were found in the gastric corpus (22.1 ± 4.0/ high power field [HPF] vs 32.0 ± 10.1/HPF; P = 0.034) and ascending colon (44.8 ± 10.4/HPF vs 60.4 ± 24.3/HPF; P = 0.047).

CONCLUSIONS

Mucosal MC counts in the pediatric GI tract are higher than previously reported, with a considerable overlap between healthy and GFA patients. These results provide detailed information on distribution and numbers of MCs in pediatric allergic patients while allowing estimates of physiological values in childhood for the first time. With regard to diagnostic procedures in GFA further laboratory parameters have to be integrated.

Mast Cell and Eosinophil Counts in Gastric and Duodenal Biopsy Specimens From Patients With and Without Eosinophilic Gastroenteritis

BACKGROUND & AIMS

Mast cells are believed to contribute to the development of eosinophilic gastrointestinal disorders (EGIDs). We quantified mast cells and eosinophils in biopsy specimens from patients with EGIDs and without known esophageal or gastrointestinal disease to investigate associations between these cell types and EGID and its features.

METHODS

We conducted a retrospective study of patients with EGID (n = 52) and of children and adults who underwent upper endoscopy and were found to have no evidence of gastrointestinal or systemic conditions (n = 123). We re-reviewed archived gastric and duodenal biopsy specimens to quantify mast cells (by tryptase immunohistochemistry) and eosinophils. We calculated the specificity of cell count thresholds for identification of patients with EGIDs and evaluated the correlation between mast cell and eosinophil counts and clinical and endoscopic features.

RESULTS

In the gastric biopsy specimens from patients without esophageal or gastrointestinal diseases, the mean mast cell count was 18.1 ± 7.2 cells per high-power field (hpf), and the peak mast cell count was 21.9 ± 8.2 cells/hpf. In the duodenal biopsy specimens from patients without esophageal or gastrointestinal diseases, the mean mast cell count was 23.6 ± 8.1 cells/hpf and the peak mast cell count was 28.1 ± 9.3 cells/hpf. The mean and peak eosinophil counts in gastric biopsy specimens from patients without disease were 3.8 ± 3.6 eosinophils/hpf and 5.8 ± 5.0 eosinophils/hpf; the mean and peak eosinophil counts in duodenal biopsy specimens were 14.6 ± 8.9 eosinophils/hpf and 19.5 ± 11.0 eosinophils/hpf. A mean count of 20 eosinophils/hpf in gastric biopsy specimens or 30 eosinophils/hpf in duodenal biopsy specimens identified patients with EGIDs with high specificity. Gastric and duodenal biopsy specimens from patients with EGIDs had significant increases in mean mast cell counts compared with biopsy specimens from patients without EGIDs. There was a correlation between mean mast cell and eosinophil counts in duodenal biopsy specimens (R = 0.47; P = .01). The mean mast cell and eosinophil counts did not correlate with symptoms or endoscopic features of EGIDs.

CONCLUSIONS

We identified thresholds for each cell type that identified patients with EGIDs with 100% specificity. The increased numbers of mast cells and eosinophils in gastric and duodenal tissues from patients with EGIDs supports the concept that these cell types are involved in pathogenesis. However, cell counts are not associated with symptoms or endoscopic features of EGIDs.

Acute Herpes Simplex Esophagitis in an Immunocompetent Adult with Eosinophilic Esophagitis

Herpes simplex esophagitis (HSE) represents a rare entity in immunocompetent patients and has infrequently been described in association with eosinophilic esophagitis (EoE). Causality in this rare association remains a debated topic. We present a case of HSE occurring in an immunocompetent adult with EoE and review the literature in support of EoE induced mucosal disruption predisposing to increased risk of HSE.

Developing a standardized approach for assessing mast cells and eosinophils on tissue biopsies: A Work Group Report of the AAAAI Allergic Skin Diseases Committee

Mast cells and eosinophils are commonly found, expectedly or unexpectedly, in human tissue biopsies. Although the clinical significance of their presence, absence, quantity, and quality continues to be investigated in homeostasis and disease, there are currently gaps in knowledge related to what constitutes quantitatively relevant increases in mast cell and eosinophil number in tissue specimens for several clinical conditions. Diagnostically relevant thresholds of mast cell and eosinophil numbers have been proposed and generally accepted by the medical community for a few conditions, such as systemic mastocytosis and eosinophilic esophagitis. However, for other mast cell- and eosinophil-associated disorders, broad discrepancies remain regarding diagnostic thresholds and how samples are processed, routinely and/or specially stained, and interpreted and/or reported by pathologists. These discrepancies can obfuscate or delay a patient's correct diagnosis. Therefore, a work group was assembled to review the literature and develop a standardized consensus for assessing the presence of mast cells and eosinophils for a spectrum of clinical conditions, including systemic mastocytosis and cutaneous mastocytosis, mast cell activation syndrome, eosinophilic esophagitis, eosinophilic gastritis/enteritis, and hypereosinophilia/hypereosinophilic syndrome. The intent of this work group is to build a consensus among pathology, allergy, dermatology, hematology/oncology, and gastroenterology stakeholders for qualitatively and quantitatively assessing mast cells and eosinophils in skin, gastrointestinal, and bone marrow pathologic specimens for the benefit of clinical practice and patients.

Lower esophageal sphincter muscle of patients with achalasia exhibits profound mast cell degranulation

BACKGROUND

Eosinophils and mast cells are key effectors of allergy. When they accumulate in the esophagus, their myoactive, pro-inflammatory, and cytotoxic products potentially could cause achalasia-like motility abnormalities and neuronal degeneration. We hypothesized that there is an allergy-mediated form of achalasia.

METHODS

LES muscle samples obtained during Heller myotomy from patients with achalasia or EGJ outflow obstruction (EGJOO) and from organ donor controls were immunostained for tryptase. Eosinophil and mast cell density, and mast cell degranulation were assessed. LES muscle was evaluated by qPCR for genes mediating smooth muscle Ca²⁺ handling and contraction.

KEY RESULTS

There were 13 patients (7 men, median age 59; 10 achalasia, 3 EGJOO) and 7 controls (4 men, median age 42). Eosinophils were infrequent in LES muscle, but mast cells were plentiful. Patients and controls did not differ significantly in LES mast cell density. However, 12 of 13 patients exhibited profound LES mast cell degranulation involving perimysium and myenteric plexus nerves, while only mild degranulation was seen in 2 of 7 controls. Hierarchical clustering analysis of qPCR data revealed two "mototype" LES gene expression patterns, with all type II patients in one mototype, and type I and III patients in the other.

CONCLUSIONS & INFERENCES

LES muscle of patients with achalasia or EGJOO exhibits striking mast cell degranulation, and patients with different achalasia manometric phenotypes exhibit different LES patterns of expression for genes mediating Ca²⁺ handling and muscle contraction. Although these findings are not definitive, they support our hypothesis that achalasia can be allergy-driven.

Mast cell effects on esophageal smooth muscle and their potential role in eosinophilic esophagitis and achalasia

Mast cells and eosinophils are the key effector cells of allergic disorders. Although most studies on eosinophilic esophagitis (EoE), an allergic disorder of the esophagus, have focused on the role of eosinophils, recent studies suggest a major role for mast cells in causing the clinical manifestations of this disease. Cellular and animal studies have demonstrated that mast cells can cause esophageal muscle cells to proliferate and differentiate into a more contractile phenotype, and that mediators released by degranulating mast cells such as tryptase and histamine can activate smooth muscle contraction pathways. Thus, activated mast cells in the esophageal muscularis propria might cause esophageal motility abnormalities, including the failure of lower esophageal sphincter relaxation typical of achalasia. In addition, mast cells have been implicated in the pathogenesis of a number of neurodegenerative disorders of the central nervous system such as Alzheimer's and Parkinson's diseases, because degranulating mast cells release proinflammatory and cytotoxic mediators capable of damaging neurons. Such mast cell degranulation in the myenteric plexus of the esophagus could cause the loss of enteric neurons that characterizes achalasia. In this report, we review the molecular mechanisms of esophageal smooth muscle contraction, and how mast cells products might affect that muscle and cause neurodegeneration in the esophagus. Based on these data, we present our novel, conceptual model for an allergy-induced form of achalasia mediated by mast cell activation in the esophageal muscularis propria.

Eosinophils in Eosinophilic Esophagitis: The Road to Fibrostenosis is Paved With Good Intentions

Eosinophilic esophagitis (EoE) is an antigen-driven disease associated with epithelial barrier dysfunction and chronic type 2 inflammation. Eosinophils are the defining feature of EoE histopathology but relatively little is known about their role in disease onset and progression. Classically defined as destructive, end-stage effector cells, eosinophils (a resident leukocyte in most of the GI tract) are increasingly understood to play roles in local immunity, tissue homeostasis, remodeling, and repair. Indeed, asymptomatic esophageal eosinophilia is observed in IgE-mediated food allergy. Interestingly, EoE is a potential complication of oral immunotherapy (OIT) for food allergy. However, we recently found that patients with peanut allergy may have asymptomatic esophageal eosinophilia at baseline and that peanut OIT induces transient esophageal eosinophilia in most subjects. This is seemingly at odds with multiple studies which have shown that EoE disease severity correlates with tissue eosinophilia. Herein, we review the potential role of eosinophils in EoE at different stages of disease pathogenesis. Based on current literature we suggest the following: (1) eosinophils are recruited to the esophagus as a homeostatic response to epithelial barrier disruption; (2) eosinophils mediate barrier-protective activities including local antibody production, mucus production and epithelial turnover; and (3) when type 2 inflammation persists, eosinophils promote fibrosis.