Lymphocytic disorders of the gastrointestinal tract: a review for the practicing pathologist

Number of intraepithelial lymphocytes and presence of a subepithelial band in normal colonic mucosa differs according to stainings and evaluation method

Chronic watery diarrhea is a frequent symptom. In approximately 10% of the patients, a diagnosis of microscopic colitis (MC) is established. The diagnosis relies on specific, but sometimes subtle, histopathological findings. As the histology of normal intestinal mucosa vary, discriminating subtle features of MC from normal tissue can be challenging and therefore auxiliary stainings are increasingly used. The aim of this study was to determine the variance in number of intraepithelial lymphocytes (IELs) and presence of a subepithelial band in normal ileum and colonic mucosa, according to different stains and digital assessment. Sixty-one patients without diarrhea referred to screening colonoscopy due to a positive feacal blood test and presenting with endoscopically normal mucosa were included. Basic histological features, number of IELs, and thickness of a subepithelial band was manually evaluated and a deep learning-based algorithm was developed to digitally determine the number of IELs in each of the two compartments; surface epithelium and cryptal epithelium, and the density of lymphocytes in the lamina propria compartment. The number of IELs was significantly higher on CD3-stained slides compared with slides stained with Hematoxylin-and-Eosin (HE) (p<0.001), and even higher numbers were reached using digital analysis. No significant difference between right and left colon in IELs or density of CD3-positive lymphocytes in lamina propria was found. No subepithelial band was present in HE-stained slides while a thin band was visualized on special stains. Conclusively, in this cohort of prospectively collected ileum and colonic biopsies from asymptomatic patients, the range of IELs and detection of a subepithelial collagenous band varied depending on the stain and method used for assessment. As assessment of biopsies from patients with diarrhea constitute a considerable workload in the pathology departments digital image analysis is highly desired. Knowledge provided by the present study highlight important differences that should be considered before introducing this method in the clinic.

Esophageal lymphocytosis: exploring the knowns and unknowns of this pattern of esophageal injury

INTRODUCTION

Lymphocyte-rich inflammation of the esophageal mucosa has gained increased awareness among pathologists and clinicians recently. Patients usually present with symptoms of esophageal dysfunction, including dysphagia and food bolus impaction. Endoscopy may show changes similar to eosinophilic esophagitis but may also be entirely normal ('microscopic esophagitis'). Three morphological subtypes or variant forms have been described which include lymphocytic, lichenoid and lymphocyte-predominant esophagitis. These need to be discriminated against other distinct causes of esophageal lymphocytosis, such as gastro-esophageal reflux disease and Candida infection.

AREAS COVERED

This review provides an overview of diagnostic criteria and clinical associations of the disorder and presents an algorithmic approach to diagnosis. A comprehensive literature review was conducted using PubMed, Medline and Google Scholar databases to identify articles related to lymphocyte-rich esophageal inflammation, published up to March 2024.

EXPERT OPINION

Lymphocyte-rich inflammation needs to be included in the differential diagnosis and clinical work-up of patients with esophageal dysfunction. There is currently considerable morphological overlap among published subtypes or variant forms. Follow-up studies of affected individuals are needed to formalize diagnostic parameters and identify the clinical course of disease in order to optimize treatment modalities.

RE.GA.IN.: the Real-world Gastritis Initiative-updating the updates

At the end of the last century, a far-sighted 'working party' held in Sydney, Australia addressed the clinicopathological issues related to gastric inflammatory diseases. A few years later, an international conference held in Houston, Texas, USA critically updated the seminal Sydney classification. In line with these initiatives, Kyoto Global Consensus Report, flanked by the Maastricht-Florence conferences, added new clinical evidence to the gastritis clinicopathological puzzle.The most relevant topics related to the gastric inflammatory diseases have been addressed by the Real-world Gastritis Initiative (RE.GA.IN.), from disease definitions to the clinical diagnosis and prognosis. This paper reports the conclusions of the RE.GA.IN. consensus process, which culminated in Venice in November 2022 after more than 8 months of intense global scientific deliberations. A forum of gastritis scholars from five continents participated in the multidisciplinary RE.GA.IN. consensus. After lively debates on the most controversial aspects of the gastritis spectrum, the RE.GA.IN. Faculty amalgamated complementary knowledge to distil patient-centred, evidence-based statements to assist health professionals in their real-world clinical practice. The sections of this report focus on: the epidemiology of gastritis; Helicobacter pylori as dominant aetiology of environmental gastritis and as the most important determinant of the gastric oncogenetic field; the evolving knowledge on gastric autoimmunity; the clinicopathological relevance of gastric microbiota; the new diagnostic horizons of endoscopy; and the clinical priority of histologically reporting gastritis in terms of staging. The ultimate goal of RE.GA.IN. was and remains the promotion of further improvement in the clinical management of patients with gastritis.

Microscopic colitis found together with celiac disease in a female population is associated with one episode of lymphocytic colitis

BACKGROUND

Microscopic colitis (MC) is considered a chronic disease associated with autoimmune disease, smoking, and drugs. The aim was to examine the association between MC and celiac disease, adjusted for smoking, considering subtypes and clinical course of the disease in a retrospectively collected female cohort.

METHODS

Women (n = 240), ≤ 73 years, diagnosed as MC in medical records or pathological registers were invited. One hundred and fifty-eight women accepted to be included. Participants completed a study questionnaire about sociodemographic factors, lifestyle habits, and medical history; the Rome III questionnaire; and the visual analog scale for irritable bowel syndrome (VAS-IBS). Participants were categorized into collagenous colitis (CC) (n = 92) and lymphocytic colitis (LC) (n = 66) or MC with one episode of the disease (n = 70) and refractory MC (n = 88). Presence of IBS-like symptoms were noted. Blood samples were collected and analyzed for anti-transglutaminase antibodies. Differences between groups were calculated and logistic regression was adjusted for smoking habits.

RESULTS

MC and celiac disease debuted simultaneously in half of the cases. Celiac disease was most prevalent in LC (12.1% vs. 3.3%; p = 0.05) and MC with one episode (12.9% vs. 2.3%; p = 0.01). Anti-transglutaminase antibodies were found in one patient with one episode of MC. Corticosteroid use was most often found in CC (37.0% vs. 21.2%; p = 0.037) and refractory MC (38.6% vs. 20.0%; p = 0.015). Past smokers were most prevalent in patients with one episode of MC (54.3 vs. 29.5%; p = 0.007). Current smoking was the smoking habit with highest prevalence of IBS-like symptoms. When adjusted for smoking habits, celiac disease was associated with LC (OR: 4.222; 95% CI: 1.020-17.469; p = 0.047) and tended to be inversely associated with refractory MC (OR: 0.210; 95% CI: 0.042-1.506; p = 0.058).

CONCLUSION

Celiac disease is most common in patients with one episode of LC. The question remains whether LC in combination with celiac disease should be classified as celiac disease or two different entities.

[Lymphocytic "…itis", from esophagus to large bowel]

Intra-epithelial lymphocytosis is an elementary lesion frequently observed in the gastrointestinal tract, which can be found from the esophagus to the colon. Many conditions of a varied nature (dysimmunitary diseases, drugs, infections…) are associated with intra-epithelial lymphocytosis, and the etiological diagnosis most often requires an anatomo-clinical correlation. The pathologist will have to identify histological lesions associated with intra-epithelial lymphocytosis allowing the diagnosis to be oriented in order to propose appropriate treatment. In this review, the main entities associated with digestive intra-epithelial lymphocytosis will be presented, detailing the key elements allowing their diagnosis.

Case-control study of the concurrence of coeliac disease with inflammatory bowel disease

BACKGROUND AND AIMS

Previous studies suggested that inflammatory bowel disease (IBD) is associated with an increased prevalence of comorbid coeliac disease. Our case-control study aimed to test this association using a large histopathology database.

METHODS

The Inform Diagnostics database is a repository of histopathologic records from patients distributed throughout the United States. In a case-control study among patients with bidirectional endoscopy, we compared the occurrence of coeliac disease in case subjects with IBD or microscopic colitis (MC) and control subjects without inflammatory colitis, calculating odds ratios (OR) and their 95% confidence intervals (CI) adjusted to the varying age, gender and ethnic distributions of case and control subjects.

RESULTS

The study population was split into 12,816 IBD cases and 6486 MC cases, who were compared to 345,733 control subjects without colitis. A total of 2892 patients were diagnosed with coeliac disease. Of 12,816 IBD patients, 57 patients (0.4%) harboured coeliac disease compared to 0.7% (2548/345,733) in the control population. The prevalence of coeliac disease among MC patients was 4.4% (288/6486). The corresponding ORs were significantly decreased in IBD (OR: 0.50, CI: 0.38-0.64) and significantly increased in MC patients (6.78, 5.96-7.69). Further stratification of the case populations into subtypes of IBD (Crohn's disease or ulcerative colitis) and MC (collagenous or lymphocytic colitis) similarly revealed significantly decreased and increased ORs for each subtype.

CONCLUSIONS

The previously reported positive association between coeliac disease and IBD may have been possibly biased by the inclusion of MC cases in the IBD patient population.

Microscopic colitis in Northern Ireland: an updated clinicopathological audit and assessment of compliance with European guidelines

AIM

We previously reported the first population-based study of the epidemiology of microscopic colitis in Northern Ireland. The aim of the current study is to provide updated data on incidence, diagnostic methods and clinicopathological associations, following dissemination of the previous report. A further aim was to compare the findings against relevant recommendations from the 2020 European guidelines.

METHOD

Study cases were identified via the Belfast Health and Social Care Trust pathology laboratory system for new cases of collagenous colitis or lymphocytic colitis diagnosed from 2017 to 2020 inclusive. Demographic and clinical information was collated from electronic healthcare records.

RESULTS

Two hundred and seventeen new diagnoses of microscopic colitis were made between 2017 and 2020, comprising 89 (41%) collagenous colitis and 128 (59%) lymphocytic colitis. The overall incidence of microscopic colitis, expressed per 100,000 adult population, ranged from 7.6 to 11.5 (5.9 to 9.0 per 100,000 total population). The 2019 peak of 11.5 cases per 100,000 adult population represents a 71.6% increase in incidence compared with the mean incidence of 6.7 per 100,000 adult population from previous data for 2008-2016. There has also been a significant increase in number of cases diagnosed on separate sampling from the right and left colon (85% in 2019-2020 compared with 30% in 2008-2016; p < 0.001). Overall compliance with coeliac serology testing has improved, with 89% tested in 2017-2018 compared with 75% in 2008-2016.

CONCLUSION

Clinicopathological communication has contributed to an increased incidence of microscopic colitis in Northern Ireland through better endoscopic diagnostic sampling and pathology coding practices. Coeliac serology testing has also improved, although continued clinical awareness is required of the need for coeliac serology testing in all patients diagnosed with microscopic colitis.

Temporal changes in the histology of microscopic colitis

BACKGROUND

In a subgroup of patients with microscopic colitis [MC], its histopathology changed from lymphocytic [LC] to collagenous colitis [CC] and vice versa. Previous studies have also observed histopathological transitions between MC and inflammatory bowel disease [IBD].

AIMS

The aim of the present study was to analyse the prevalence of such transitions in a large population of MC patients.

METHODS

The Inform Diagnostics database is an electronic repository of histopathology records of patients distributed throughout the USA. In a cross-sectional study, we analysed the prevalence of changes in MC histology. Each prevalence was expressed as the rate per 100 MC patients with its 95% Poisson confidence interval.

RESULTS

In a total population of 29 307 MC patients, our cross-sectional study focused on a subgroup of 4363 patients who underwent two or more consecutive colonoscopies between December 2008 and March 2020. Overall, 1.6% [95% CI 1.2-2.0%] of patients changed their MC phenotype from LC to CC, and 0.5% [0.3-0.7%] from CC to LC. Of 4363 MC patients, 414 [9.5%] were also diagnosed with IBD. In 2.9% [2.4-3.5%], MC and IBD were diagnosed as synchronous mucosal lesions. In 2.1% [1.7-2.6%], MC changed to IBD, and in 4.5% [3.9-5.2%] IBD changed to MC.

CONCLUSIONS

The analysis confirmed the synchronous occurrence of MC and IBD and transitions between the two diagnoses. In patients who fail therapy for either one of the two diseases, the gastroenterologist should search for changes in the underlying phenotype as a possible explanation.

Insights into the underlying mechanisms and clinical management of microscopic colitis in relation to other gastrointestinal disorders

Microscopic colitis (MC) is a chronic inflammatory disease of the large intestine and as a relatively late recognized condition, its relationship with other disorders of the gastrointestinal tract is gradually being understood and investigated. As a multifactorial disease, MC interacts with inflammatory bowel disease, celiac disease, and irritable bowel syndrome through genetic overlap, immunological factors, and gut microflora. The risk of colorectal cancer was significantly lower in MC, gastrointestinal infections increased the risk of developing MC, and there was an inverse association between Helicobacter pylori infection and MC. A variety of associations are found between MC and other gastrointestinal disorders, where aspects such as genetic effects, resemblance of immunological profiles, and intestinal microecology are potential mechanisms behind the relationships. Clinicians should be aware of these connections to achieve a better understanding and management of MC.

The Occurrence of Gastritis in Microscopic Colitis and Inflammatory Bowel Disease

Multiple studies have shown that Helicobacter pylori infection is associated with a lower prevalence of inflammatory bowel disease (IBD).^1,2 Besides chronic active gastritis (CAG) resulting from gastric infection with H pylori, pathologists have noticed another form of CAG, which is unrelated to H pylori infection and seems to cluster in patients with IBD.^3-5 The aim of the present study was to compare the prevalence of H pylori-negative and H pylori-positive CAG in patients with IBD, and microscopic colitis (MC).

Pathogenesis of Microscopic Colitis: A Systematic Review

BACKGROUND

Whereas the exact aetiology of microscopic colitis [MC] remains unknown, a dysregulated immune response to luminal factors or medications is the most accepted pathogenesis hypothesis.

METHODS

We conducted a systematic review of the pathogenesis of MC. We applied the Joanna Briggs Institute methodologies and the PRISMA statement for the reporting of systematic reviews [PROSPERO Trial Identifier: CRD42020145008]. Populations, Exposure of interest, and Outcome [PEO] questions were used to explore the following topics in MC: 1] intestinal luminal factors; 2] autoimmunity; 3] innate immunity; 4] adaptive immunity; 5] extracellular matrix; 6] genetic risk factors; and 7] mechanism of diarrhoea. A search was done in PubMed, Embase, and Web of Science up to February 2020. A narrative description was performed explaining the findings for each aspect of MC aetiopathogenesis.

RESULTS

Thirty-eight documents provided evidence for PEO1, 100 for PEO2, 72 for PEO3 and 4, 38 for PEO5, 20 for PEO6, and 23 for PEO7. The majority of documents were cohorts, case reports, and case series, with a few case-control and some experimental studies. Consistency among data provided by different studies was considered to support pathogenetic hypotheses. MC is a multifactorial disease believed to involve innate and adaptive immune responses to luminal factors, genetic risk, autoimmunity, and extracellular matrix alterations, all contributing by varied mechanisms to watery diarrhoea.

CONCLUSIONS

This is the first systematic review on the aetiology of MC supporting the notion that MC is a multifactorial disease. However, high-profile studies are lacking, and most evidence derives from small heterogeneous studies.

Sampling and Reporting of Inflammatory Bowel Disease

Pathologists have an important and expanding role in the diagnosis and management of inflammatory bowel disease. This role includes the initial diagnosis of the disease, assessment of the response to treatment and the identification of short-term complications such as cytomegalovirus infection and long-term complications such as dysplasia. Furthermore, the assessment of resection specimens for complication of disease is important to determining the risk of subsequent disease or inflammation within an ileal pouch. Adequate sampling of the disease at endoscopy and from the surgical resection specimen is vital to determining the ultimate information that can be provided by the pathologist. This sampling is determined by the clinical scenario. Similarly, a standardized approach to reporting and synthesizing the histologic findings will improve patient management. This is best exemplified by the increasing interest in histologic activity indices, such as the Nancy index in ulcerative colitis, and in the standardized reporting for inflammatory bowel disease dysplasia recommended by the SCENIC international consensus.

Gh BF, Taherkhani A, Rostami-Nejad M, Asri N, Haidari MH. Screening of Altered Metabolites and Metabolic Pathways in Celiac Disease Using NMR Spectroscopy

BACKGROUND

Celiac disease (CeD) is an autoimmune intestinal disorder caused by gluten protein consumption in genetically predisposed individuals. As biopsy sampling is an invasive procedure, finding novel noninvasive serological markers for screening of at-risk CeD population is a priority. Metabolomics is helpful in monitoring metabolite changes in body fluids and tissues. In the present study, we evaluated serum metabolite levels of CeD patients relative to healthy controls with the aim of introducing new biomarkers for population screening.

METHOD

We compared the serum metabolic profile of CeD patients (n = 42) and healthy controls (n = 22) using NMR spectroscopy and multivariate analysis.

RESULT

25 metabolites were identified by serum metabolic profiling. Levels of 3-hydroxyisobutyric acid and isobutyrate showed significant differences in CeD patients' samples compared with healthy controls (p < 0.05). According to pathway analysis, our data demonstrated that changes in nine metabolic pathways were significantly disrupted/affected in patients with CeD. These enriched pathways are involved in aminoacyl-tRNA biosynthesis; primary bile acid biosynthesis; nitrogen metabolism; glutamine and glutamate metabolism; valine, leucine, and isoleucine biosynthesis and degradation; taurine and hypotaurine metabolism; glyoxylate and dicarboxylate metabolism; glycine, serine, and threonine metabolism; and arginine biosynthesis.

CONCLUSION

In summary, our results demonstrated that changes in the serum level of 25 metabolites may be useful in distinguishing CeD patients from healthy controls, which have the potential to be considered candidate biomarkers of CeD.

Neutrophils, eosinophils, and intraepithelial lymphocytes in the squamous esophagus in subjects with and without gastroesophageal reflux symptoms

Whilst intraepithelial lymphocytes (IELs) are considered normal within the distal esophageal mucosa, they have an increasingly recognised role in the pathogenesis of reflux esophagitis, and IEL quantification establishes the diagnosis of lymphocytic esophagitis. Knowledge regarding the upper limit of a normal IEL count in health is lacking. We studied 117 non-healthcare seeking adult volunteers from a random community sample (the Kalixanda study) with esophageal biopsies 2 cm above the gastroesophageal junction. Subjects were divided into four groups based on the presence or absence of gastro-esophageal reflux symptoms and/or esophagitis on endoscopy. Asymptomatic subjects with no endoscopic esophagitis were selected as controls, and the cell counts in this group were used to define the upper limit of normal of IELs, eosinophils and neutrophils. The entire sample was used to identify independent predictors of increased cellular counts by logistic regression analysis. None of the healthy controls had an IEL count of more than three per five high power fields (HPF), and therefore this was considered as the upper limit of normal; no controls had eosinophils or neutrophils in esophageal biopsies. Independent predictors of an elevated IEL count were spongiosis on histology (OR 11.17, 95% CI 3.32-37.58, P < 0.01) and current smoking (OR 4.84, 95% CI 1.13-2.71, P = 0.03). A receiver operating characteristics analysis concluded that a threshold of 3 IELs/5HPFs performs best in predicting reflux symptoms when a normal esophageal mucosa is visualized on endoscopy (sensitivity = 100.0%, specificity = 35.2%). The healthy esophageal mucosa does not contain more than three IELs per five HPF in the distal esophagus.

Duodenal intraepithelial lymphocytosis in Helicobacter pylori gastritis: comparison before and after treatment

Our aims were to assess performance of duodenal intraepithelial lymphocyte counting for diagnosis of Helicobacter pylori (H. pylori) gastritis, and effects of eradication therapy on intraepithelial lymphocytosis. Paired duodenal and gastric biopsies from subjects with a pathologic diagnosis of H. pylori gastritis were reviewed. Higher duodenal intraepithelial lymphocyte counts were observed in 40 subjects with H. pylori gastritis (26 ± 5 per villus) than 52 subjects negative for H. pylori (12 ± 2 per villus). After successful eradication therapy, duodenal lymphocytes were indistinguishable from H. pylori-negative subjects, whereas they remained elevated after failed eradication therapy. This study confirms previous reports of increased duodenal intraepithelial lymphocytes in patients with concurrent Helicobacter pylori gastritis. Intraepithelial lymphocyte counts of > 15 per villus or > 10 per 100 enterocytes were predictive of infection. Duodenal lymphocytosis decreases significantly after successful eradication therapy but remains elevated when treatment fails.

Normal gastrointestinal tract inflammatory cells and review of select benign hematolymphoid proliferations

The luminal gastrointestinal tract can be a site of robust immune response in which reactive lymphoproliferative processes can sometimes be difficult to distinguish from lymphoma. In this article, we review gastrointestinal tract normal resident inflammatory cells and common nonneoplastic lymphoproliferative responses with emphasis on their differential and links to lymphoma. Topics that are covered include lymphocytic esophagitis, gastric chronic inflammation, mucosa-associated lymphoid tissue, and ulceration, small intestinal lymphoid hyperplasia, celiac disease, microscopic colitis, inflammatory bowel disease, primary immunodeficiency, graft-versus-host disease, and anti-programmed cell death protein-1 effect. We additionally present the less common differential of histiocytic processes within the gastrointestinal tract. The aim of this paper is to serve as a reference for practicing pathologists facing lymphoid, lymphoplasmacytic, or histiocytic processes in the luminal gastrointestinal tract. We hope to help the practicing pathologist distinguish benign from malignant entities and identify features requiring further workup.

European guidelines on microscopic colitis: United European Gastroenterology and European Microscopic Colitis Group statements and recommendations

INTRODUCTION

Microscopic colitis is a chronic inflammatory bowel disease characterised by normal or almost normal endoscopic appearance of the colon, chronic watery, nonbloody diarrhoea and distinct histological abnormalities, which identify three histological subtypes, the collagenous colitis, the lymphocytic colitis and the incomplete microscopic colitis. With ongoing uncertainties and new developments in the clinical management of microscopic colitis, there is a need for evidence-based guidelines to improve the medical care of patients suffering from this disorder.

METHODS

Guidelines were developed by members from the European Microscopic Colitis Group and United European Gastroenterology in accordance with the Appraisal of Guidelines for Research and Evaluation II instrument. Following a systematic literature review, the Grading of Recommendations Assessment, Development and Evaluation methodology was used to assess the certainty of the evidence. Statements and recommendations were developed by working groups consisting of gastroenterologists, pathologists and basic scientists, and voted upon using the Delphi method.

RESULTS

These guidelines provide information on epidemiology and risk factors of microscopic colitis, as well as evidence-based statements and recommendations on diagnostic criteria and treatment options, including oral budesonide, bile acid binders, immunomodulators and biologics. Recommendations on the clinical management of microscopic colitis are provided based on evidence, expert opinion and best clinical practice.

CONCLUSION

These guidelines may support clinicians worldwide to improve the clinical management of patients with microscopic colitis.

Distribution of histopathological features along the colon in microscopic colitis

PURPOSE

The diagnosis microscopic colitis (MC) consisting of collagenous colitis (CC) and lymphocytic colitis (LC) relies on histological assessment of mucosal biopsies from the colon. The optimal biopsy strategy for reliable diagnosis of MC is controversial. The aim of this study was to evaluate the distribution of histopathological features of MC throughout the colon.

METHODS

Mucosal biopsies from multiple colonic segments of patients with MC who participated in one of the three prospective European multicenter trials were analyzed. Histological slides were stained with hematoxylin-and-eosin, a connective tissue stain, and CD3 in selected cases.

RESULTS

In total, 255 patients were included, 199 and 56 patients with CC and LC, respectively. Both groups exhibited a gradient with more pronounced inflammation in the lamina propria in the proximal colon compared with the distal colon. Similarly, the thickness of the subepithelial collagenous band in CC showed a gradient with higher values in the proximal colon. The mean number of intraepithelial lymphocytes was > 20 in all colonic segments in patients within both subgroups. Biopsies from 86 to 94% of individual segments were diagnostic, rectum excluded. Biopsies from non-diagnostic segments often showed features of another subgroup of MC.

CONCLUSION

Conclusively, although the severity of the histological changes in MC differed in the colonic mucosa, the minimum criteria required for the diagnosis were present in the random biopsies from the majority of segments. Thus, our findings show MC to be a pancolitis, rectum excluded, questioning previously proclaimed patchiness throughout the colon.

Minimal Lesions of the Small Intestinal Mucosa: More than Morphology

Minimal lesions of the small bowel are mucosal changes characterized by an increased number of intraepithelial lymphocytes (with or without crypt hyperplasia) and normal villous architecture. Such changes are associated with a wide spectrum of conditions, ranging from food intolerances to infections, and from drugs to immune diseases, with different clinical profiles and manifestations, which complicates the formulation of a differential diagnosis. Patient history, symptom evaluation, and histopathology are the diagnostic features needed to establish a correct diagnosis. Physicians should assist pathologists in formulating a precise morphological evaluation by taking well-oriented small intestinal biopsies and collecting informative clinical findings that inform histopathology. In this current clinical controversy, the authors provide the reader with an appraisal of the small intestine minimal lesions through a careful analysis of the major conditions (e.g., celiac disease and other non-celiac disorders) responsible for such changes and their differential diagnosis. Also, we acknowledge that some of the diseases detailed in this article may progress from an early minimal lesion to overt mucosal atrophy. Thus, the timing of the diagnosis is of paramount importance.

Seasonal Variation of Duodenal Intraepithelial Lymphocytosis

The increase of intraepithelial lymphocytes in architecturally normal duodenal mucosa is commonly referred to as duodenal intraepithelial lymphocytosis (DIL). The characteristic appearance of DIL corresponds with Marsh grade 1, that is, normal or mild increase in lamina propria inflammation of the duodenal mucosa, with no crypt hyperplasia or villous atrophy.¹ Approximately 11% of DIL patients harbor clinical and serologic features suggestive of gluten sensitivity.² An additional 2% of patients with DIL harbor concomitant microscopic colitis.³Helicobacter pylori gastritis may contribute to another 10%-15% of DIL, which may resolve following eradication of H pylori.⁴ In the majority of cases with DIL, however, its underlying cause has remained unknown.¹ A study of the seasonal variations in the occurrence of DIL may provide additional clues about its yet unknown etiology.

Autoimmune gastritis

Autoimmune gastritis (AIG) is an increasingly prevalent, organ-specific, immune-mediated disorder characterized by the destruction of gastric parietal cells, leading to the loss of intrinsic factor and reduced acid output. These alterations result in malabsorption of iron, vitamin B₁₂ (pernicious anaemia) and potentially other micronutrients. For several years, most studies have focused on pernicious anaemia only, generating confusion between the two entities. In AIG, the gastric proton pump, H⁺/K⁺ ATPase, is the major autoantigen recognized by autoreactive T cells. The T cell-dependent activation of B cells stimulates the production of anti-parietal cell antibodies, the serological hallmark of AIG. The role of Helicobacter pylori infection in activating or favouring the autoimmune process is still uncertain. Early histopathological alterations allowing a more precise and prompt recognition have recently been described. AIG is burdened by a substantial diagnostic delay as it can present with varied clinical signs including, among others, gastrointestinal symptoms and neuropsychiatric manifestations. In advanced stages, AIG might progress to neuroendocrine tumours and gastric adenocarcinoma. Management includes early detection through a proactive case-finding strategy, micronutrient supplementation and endoscopic surveillance. This Primer comprehensively describes the most important insights regarding the epidemiology, pathophysiology, diagnosis and management of AIG, focusing on the most controversial, outstanding issues and future directions.

Immune-related acute and lymphocytic gastritis in a patient with metastatic melanoma treated with pembrolizumab immunotherapy

Here, we present a case of acute and lymphocytic gastritis related to therapy with pembrolizumab for metastatic melanoma. After an asymptomatic phase with moderate histological inflammation (observed at 9 months of immunotherapy), gastritis became symptomatic and severe on repeated biopsies (13 months after the beginning of pembrolizumab). Symptoms and histological lesions both improved with proton pump inhibitor and steroid therapy, as well as interruption of pembrozulimab. The interest of this case lays in the relative rarity of gastritis over small and large intestinal inflammatory lesions caused by immune checkpoint inhibitors as well as in the features of the inflammatory infiltrate, which may be purely lymphocytic (mainly T-cells, with a prevalence of CD8+ over CD4+ lymphocytes) or mixed lymphocytic and granulocytic, requiring the exclusion of other causes of disease. To our knowledge, only 7 cases of immune-related gastritis have been previously documented in the current literature, of which 4, included the current one, were exclusively associated with pembrozulimab therapy.

Topography, morphology, and etiology of lymphocytic gastritis: a single institution experience

Lymphocytic gastritis (LG) is an uncommon reaction pattern of gastric injury characterized by intraepithelial lymphocytosis of the surface foveolar epithelium and chronic inflammation in the lamina propria. It most commonly occurs in association with gluten-sensitive enteropathy, Helicobacter pylori gastritis, non-steroidal anti-inflammatory drugs, and microscopic colitis. While the topography of LG has been described in gluten-sensitive enteropathy and H. pylori infection, no definite morphologic features have been used to further subcategorize LG based on possible etiologies. Furthermore, new immunotherapy agents have been associated with lymphocytic infiltrate in the gastrointestinal tract, but their association with LG has not been reported. Cases of LG were collected from our institution in the period between August 2011 and September 2017. The topography of LG and morphologic features such as glandular microabscesses, intestinal metaplasia, lymphoid aggregates, surface vs pit distribution of lymphocytes, and number of intraepithelial lymphocytes per 100 epithelial cells were assessed for each case using the updated Sydney System where applicable. Twenty-seven cases of LG were identified in the recent 6-year period at our institution. Gluten-sensitive enteropathy is the main reported cause of LG followed by NSAID injury. Cases of LG associated with gluten-sensitive enteropathy are antral predominant, those associated with H. pylori are body predominant, and those occurring in the setting of NSAID injury show pangastritis. Glandular microabscesses are observed in all cases of LG associated with H. pylori, and not in the setting of GSE or NSAID injury. In addition, a case of LG associated with melanoma immunotherapy has been identified. Topography and morphology of lymphocytic gastritis may point to the cause of injury, allowing for proper treatment of the underlying disease.

Microscopic colitis and its associations with complications observed in classic inflammatory bowel disease: a systematic review

Objectives: Crohn's disease and ulcerative colitis are associated with an increased risk to develop anemia, cutaneous diseases, liver diseases, malignancy, osteoporosis, rheumatic diseases, thromboembolism and uveitis. The association between these diseases and microscopic colitis (MC) is not known. The aim of the present systematic review was to examine associations between MC and diseases observed in association with Crohn's disease and ulcerative colitis.Material and methods: According to the review protocol, original articles which described the prevalence of abovementioned diseases in relation to MC, were searched for in PubMed, Embase and Web of Science.Results: After exclusion of duplicates, 928 articles remained. Based on relevancy of their title, abstract or type of article, 16 articles were ordered in full text and after assessment, nine articles could be included in the review. A second research strategy with individual diseases rendered further two articles. Seven articles covered malignancy/neoplasia, where four showed no association with malignancy and three a reduced association compared with controls. Four articles covering rheumatic diseases showed an association between these diseases and MC. One study showed an association between MC and osteoporosis, whereas one did not. One study showed an association between MC and cutaneous diseases, whereas anemia, eye diseases and thromboembolism showed no associations.Conclusions: Due to short follow-up time in small studies, with selection bias due to exclusion of former or prevalent malignancy in an older population, no conclusions can be drawn concerning the true association between MC and malignancy. Rheumatic diseases seem to be associated with MC.

Practical Approach to the Histologic Diagnosis of Gastrointestinal Lymphomas Through the First-line Marker Battery of CD20, CD3, CD30, and Epstein-Barr Virus-encoded RNAs

The gastrointestinal (GI) tract is a prevalent site for extranodal lymphomas. Some subtypes of GI tract lymphomas are aggressive and have dismal clinical outcomes. Therefore, prompt histopathologic detection of such types can be very important. We thus introduce a practical approach in the histopathologic diagnosis of GI lymphomas according to the revised World Health Organization (WHO) classification. When lymphocyte proliferation is found in the GI tract, a stepwise approach can help narrow down the differential diagnoses. When considering subtype incidence, macroscopic findings, and microscopic patterns, applying a first-line marker battery of CD20, CD3, CD30, and Epstein-Barr virus-encoded RNAs can effectively narrow down the top differential diagnoses at the initial step. Generally, the most common subtype among GI tract lymphomas is B-cell non-Hodgkin lymphoma identified by CD20 expression, followed by T-cell and NK-cell non-Hodgkin lymphomas identified by the CD3 expression, and some subtypes are defined by Epstein-Barr virus infection or CD30 expression. Macroscopically, lymphomas present as various gross types, such as large masses, small lesions, superficial and shallow lesions, polyp-like or polyposis-like features, or ulcer/necrosis/perforation. Microscopically, large pleomorphic cells or small to medium-sized tumor cells grow with various architectures and tumor microenvironments. Incorporation of macroscopic and microscopic features and the stepwise immunophenotyping may be a practical approach to the differential diagnosis of aggressive lymphoma, indolent/low-grade lymphoma, or benign to indolent lymphoproliferative disease. Exceptions always exist; this approach focuses on the relatively prevalent circumstances of lymphomatous lesions initially encountered in the GI tract.

Lymphocytic gastritis induced by pembrolizumab in a patient with metastatic melanoma

Immune checkpoint inhibitors such as programmed cell death-1 inhibitor pembrolizumab have been shown to be effective in metastatic malignancies such as advanced melanoma. Immune-related adverse effects on multiple organs have been described, such as colitis, skin rash, and hypothyroidism. We present the case of a 44-year-old man with advanced melanoma and recurrent lung metastases who developed symptoms of dyspepsia and gastroesophageal reflux disease after 1 month of therapy with pembrolizumab. Gastric biopsy showed histologic features consistent with lymphocytic gastritis, which was absent on a biopsy 2 months before initiation of therapy. Lymphocytic infiltrates likely secondary to increased autoimmunity after use of immunotherapy have been observed in the colon; however, such histologic findings in the upper gastrointestinal tract have yet to be described. Here, we present a case of lymphocytic gastritis in a patient treated with pembrolizumab, suggesting a new manifestation of toxicity.

Biopsy Diagnosis of Celiac Disease: The Pathologist's Perspective in Light of Recent Advances

Celiac disease is a common immune-mediated disorder that occurs in individuals with permissive genetics (HLA-DQ2/DQ8 genotype) following exposure to certain wheat proteins. The histopathologic manifestations of small intestinal mucosal injury (villus atrophy, crypt hyperplasia, and intraepithelial lymphocytosis) are well recognized. However, these findings are not specific for celiac disease, because they are observed in other small intestinal disorders. These mimics include common and rare entities, the list of which continues to grow. This article discusses the histopathology and differential diagnosis of celiac disease and provides the pathologist's perspective on biopsy adequacy, evaluation, and reporting in light of current knowledge.

Prevalence, Pathogenesis, Diagnosis, and Management of Microscopic Colitis

Microscopic colitis (MC), which is comprised of lymphocytic colitis and collagenous colitis, is a clinicopathological diagnosis that is commonly encountered in clinical practice during the evaluation and management of chronic diarrhea. With an incidence approaching the incidence of inflammatory bowel disease, physician awareness is necessary, as diagnostic delays result in a poor quality of life and increased health care costs. The physician faces multiple challenges in the diagnosis and management of MC, as these patients frequently relapse after successful treatment. This review article outlines the risk factors associated with MC, the clinical presentation, diagnosis and histologic findings, as well as a proposed treatment algorithm. Prospective studies are required to better understand the natural history and to develop validated histologic endpoints that may be used as end points in future clinical trials and serve to guide patient management.

Associations of Microscopic Colitis With Other Lymphocytic Disorders of the Gastrointestinal Tract

BACKGROUND & AIMS

Lymphocytic disorders of the upper and lower gastrointestinal tract seem to cluster in patients. We aimed to assess the frequency of comorbid occurrence of lymphocytic disorders in patients with microscopic colitis (MC).

METHODS

We collected data from the Miraca Life Sciences Database, a large national electronic repository of histopathologic records of patients throughout the United States. In a population of 228,506 patients who underwent bidirectional endoscopy from January 2008 through July 2016, we studied the comorbid occurrence of celiac disease, duodenal intraepithelial lymphocytosis, lymphocytic gastritis, and lymphocytic esophagitis among 3456 patients with MC. Associations were described in terms of their odds ratios (OR) and 95% CIs.

RESULTS

Any type of lymphocytic disorder occurred in 13.7% of patients with MC and 5.9% of patients without MC. The ORs of lymphocytic disorders in patients with MC were: 2.56 (95% CI, 2.32-2.82) for any type of lymphocytic disorder, 3.07 (95% CI, 1.25-7.52) for lymphocytic esophagitis, 15.05 (95% CI, 12.31-18.41) for lymphocytic gastritis, 1.73 (95% CI, 1.53-21.96) for duodenal intraepithelial lymphocytosis, and 6.06 (95% CI, 5.06-7.25) for celiac disease. Comorbidities were more common in patients with lymphocytic than collagenous colitis, with an OR of 1.74 (95% CI, 1.42-2.13). Patients with MC with comorbidities were significantly younger and had a lower proportion of men than patients with MC patients without comorbidities. Diarrhea was the predominant symptoms in all patients MC, irrespective of comorbidities.

CONCLUSION

In a retrospective study, we identified lymphocytic disorders of the upper gastrointestinal tract that are significantly more common in patients with than without MC. These associations suggest the existence of an underlying etiology that is common to all lymphocytic disorders and that affects the upper and lower gastrointestinal tract.

Mechanism of differentiation and regulation of CD4+ intraepithelial lymphocytes: Relationship with inflammatory bowel disease

CD4⁺ intraepithelial lymphocytes are a special type of lymphocytes located in the lower layer of the intestinal epithelium. According to the difference of cell phenotypes and functions, CD4⁺ intraepithelial lymphocytes can be divided into multiple subgroups, including Th1 cells, Th2 cells, and Th17 cells. The proliferation, differentiation, and apoptosis of CD4⁺ intraepithelial lymphocytes can be regulated by a variety of transcription factors, intestinal microbes, and nutrients. CD4⁺ intraepithelial lymphocytes play an important role in the pathogenesis of inflammatory bowel disease. In this article, we will review the mechanism of differentiation and regulation of CD4⁺ intraepithelial lymphocytes and their relationship with inflammatory bowel disease, with an aim to provide some new clues to the pathogenesis of inflammatory bowel disease.

Esophageal mucosa in HIV infection: A"deeper" look at this little spoken organ

BACKGROUND AND AIM

Although the esophagus is a common site of opportunistic infection in AIDS patients, little is known about the impact of HIV as well as opportunistic infection in the esophageal mucosa. Our aim is to analyze the esophageal immune profile in HIV+ patients with different immunological status with and without the opportunistic Candida infection.

METHODS

Immunohistochemistry to CD4⁺ and CD8⁺ T-cells, γ-interferon, transforming growth factor-β, interleukin (IL)-4, IL-6, IL-13, and IL-17 was performed in esophageal samples of 40 chronically HIV+ patients under highly active antiretroviral therapy (16 with Candida esophagitis, 12 virologically non-supressed with blood CD4 count < 500, and 12 virologically suppressed with blood CD4 count > 500; the latter two groups without esophageal candidiasis). The controls were 12 HIV-negative healthy individuals.

RESULTS

Esophageal CD4⁺ T-cell expression in HIV+ patients did not differ from the control group (P = 0.50). Mucosal CD8⁺ T-cell expression was significantly increased in HIV+ patients (P = 0.0018). Candida esophagitis and virologically non-supressed HIV+ patients with CD4 < 500 showed an increased expression of IL-17 and IL-6 with fewer expressions of γ-interferon, more attenuated in the latter group. Transforming growth factor-β was increased only in virologically suppressed HIV+ patients with CD4 > 500. IL-4 and IL-13 were similar to the control group.

CONCLUSION

In contrast to CD8⁺ T-cell expression, esophageal CD4⁺ T-cell expression does not reflect the HIV+ patient's immunological status. T-helper 17 (Th17) response seems to play a role in the esophageal mucosa of virologically non-supressed HIV+ patients with blood CD4 < 500. Candida esophagitis showed a Th1/Th17 response but seems to be dominantly regulated by the Th17 pathway.

Time trend occurrence of duodenal intraepithelial lymphocytosis and celiac disease in an open access endoscopic population

BACKGROUND

Duodenal intraepithelial lymphocytosis (DIL) is a histological finding characterized by the increase of intraepithelial CD3T-lymphocytes over the normal value without villous atrophy, mostly associated to coeliac disease (CD), Helicobacter pylori (Hp) gastritis and autoimmune diseases.

OBJECTIVE

To assess the occurrence of DIL, CD and Hp gastritis in an endoscopic population over a 13 year period.

METHODS

From 2003 to 2015 we included adult patients who consecutively underwent oesophago-gastro-duodenoscopy (OGD) with duodenal biopsies assessing the overall and annual occurrence of DIL and CD and the prevalence of Hp gastritis.

RESULTS

160 (2.3%) patients with DIL and 275 (3.9%) with CD were detected among 7001 patients. CD occurrence was higher from 2003 to 2011, while since 2012 DIL occurrence gradually increased significantly compared to CD (p = 0.03). DIL patients were more frequently female (p = 0.0006) and underwent OGD more frequently for dyspepsia (p = 0.002) and for indications not related to gastrointestinal symptoms than CD patients (p = 0.0003). Hp gastritis occurred similarly in CD and DIL patients but the latter had higher frequency of atrophic body gastritis (p = 0.005).

CONCLUSIONS

DIL is a condition increasing in the general endoscopic population mainly diagnosed by chance. Concomitant gastric histological evaluation is able in one third of DIL patients to identify associated possible causes of DIL, such as Hp and atrophic gastritis.

Recurrent anaemia in a patient with lymphocytic gastritis and vitamin B12 deficiency

Lymphocytic gastritis is an idiopathic disease, characterized by intraepithelial infiltration of large numbers of T lymphocytes and often described in association with coeliac disease and Helicobacter pylori infection. Although usually associated with iron deficiency anaemia, there is no description on the association between lymphocytic gastritis and secondary vitamin B₁₂ deficiency anaemia. We describe a rare case of recurrent anaemia in a patient with lymphocytic gastritis reversed with vitamin B₁₂ replacement.

Rare Gastric Lesions Associated with Helicobacter pylori Infection: A Histopathological Review

Helicobacter pylori infection is associated with chronic gastritis, peptic ulcer disease, gastric adenocarcinoma, and mucosa-associated lymphoid tissue lymphoma. However, some rare gastric lesions exhibiting distinctive histological features may also be associated with H. pylori infection, including lymphocytic gastritis, granulomatous gastritis, Russell body gastritis, or crystal-storing histiocytosis. Although diverse factors can contribute to their development, there is convincing evidence that H. pylori infection may play a pathogenic role. These findings are mainly based on studies in patients with these lesions who exhibited clinical and histological improvements after H. pylori eradication therapy. Thus, H. pylori eradication therapy might be indicated in patients with no other underlying disease, particularly in countries with a high prevalence of H. pylori infection. This review describes the characteristic histological features of these rare lesions and evaluates the evidence regarding a causative role for H. pylori infection in their pathogenesis.

Lymphocytic esophagitis: Still an enigma a decade later

Lymphocytic esophagitis (LE) is a clinicopathologic entity first described by Rubio et al in 2006. It is defined as peripapillary intraepithelial lymphocytosis with spongiosis and few or no granulocytes on esophageal biopsy. This definition is not widely accepted and the number of lymphocytes needed to make the diagnosis varied in different studies. Multiple studies have described potential clinical associations and risk factors for LE, such as old age, female gender and smoking history. This entity was reported in inflammatory bowel disease in the pediatric population but not in adults. Other associations include gastroesophageal reflux disease and primary esophageal motility disorders. The most common symptom is dysphagia, with a normal appearing esophagus on endoscopy, though esophageal rings, webs, nodularities, furrows and strictures have been described. Multiple treatment modalities have been used such as proton pump inhibitors and topical steroids. Esophageal dilation seems to be therapeutic when dysphagia is present along with esophageal narrowing secondary to webs, rings or strictures. The natural history of the disease remains unclear and needs to be better delineated. Overall, lymphocytic esophagitis seems to have a chronic and benign course, except for two cases of esophageal perforation in the literature, thought to be secondary to this entity.

Microscopic colitis: a missed diagnosis among patients with moderate to severe irritable bowel syndrome

OBJECTIVE

Irritable bowel syndrome (IBS) is a very common condition in general practise, affecting 10-20% of the population in the Western world. The clinical picture of diarrhoea-predominant IBS (IBS-D) resembles other chronic diarrhoeic conditions, such as microscopic colitis (MC). It is impossible to separate these by clinical examinations or lab-tests that can be done in general practise. The aim of this study was to detect any missed diagnoses when only using a symptom-based approach for the diagnosis of IBS.

MATERIAL AND METHODOLOGY

We examined 87 participants diagnosed with IBS by the Rome III criteria. All the participants underwent full clinical examination, lab-tests and colonoscopy including mucosa biopsies for histological examination.

RESULTS

The histological analysis revealed four cases of MC in participants who for years had been diagnosed with IBS. We found no biochemical or clinical markers that made it possible to differentiate between IBS and MC. MC was only found in the participants diagnosed with IBS-D.

CONCLUSION

When long-lasting, unresolved diarrhoeic conditions are present in patients over 45-50 years of age, colonoscopy with biopsy should be performed to rule out MC and other pathologies before diagnosing IBS. In younger patients with pronounced watery diarrhoea, one should consider colonoscopy individually if there is no response to IBS-treatment.

Towards a new paradigm of microscopic colitis: Incomplete and variant forms

Microscopic colitis (MC) is a chronic inflammatory bowel disease that has emerged in the last three decades as a leading cause of chronic watery diarrhoea. MC classically includes two main subtypes: lymphocytic colitis (LC) and collagenous colitis (CC). Other types of histopathological changes in the colonic mucosa have been described in patients with chronic diarrhoea, without fulfilling the conventional histopathological criteria for MC diagnosis. Whereas those unclassified alterations remained orphan for a long time, the use of the term incomplete MC (MCi) is nowadays universally accepted. However, it is still unresolved whether CC, LC and MCi should be considered as one clinical entity or if they represent three related conditions. In contrast to classical MC, the real epidemiological impact of MCi remains unknown, because only few epidemiological studies and case reports have been described. MCi presents clinical characteristics indistinguishable from complete MC with a good response to budesonide and cholestiramine. Although a number of medical treatments have been assayed in MC patients, currently, there is no causal treatment approach for MC and MCi, and only empirical strategies have been performed. Further studies are needed in order to identify their etiopathogenic mechanisms, and to better classify and treat MC.

Revisiting Pathological Criteria for Earlier Diagnosis of Coeliac Disease

OBJECTIVES

The diagnosis of coeliac disease (CD) remains sometimes difficult because the histological criteria are not fully met. The aim of this study was to refine histological diagnostic criteria of CD.

METHODS

One hundred seventy-five duodenal bulb D1 (n = 79) and duodenal D2 (n = 96) biopsies of 96 patients with CD (58 girls, mean age 7 years), 135 normal D2 biopsies (69 girls, mean age 12 years), and 64 D2 biopsies of other digestive disorders (DDs) (39 girls, mean age 13 years) obtained from children during a period of 4 years were reviewed.

RESULTS

Interobserver agreement was greater for the classification of Corazza-Villanacci than for Marsh-Oberhuber (κ = 0.812 vs κ = 0.409, respectively). Between 40 and 70 intraepithelial lymphocytes (IELs) per 100 epithelial cells (ECs), 32% of patients were CD, whereas 50% had other DD. Above 70 IELs per 100 EC, 53% were CD, and only 6% had other DD. In CD, IELs were significantly located above EC nuclei compared with other DD, (12 IELs/100 EC vs 2 IELs/100 EC, respectively). In 21% of CD cases, D2 were normal and the diagnosis could only be made on D1. Finally, 6% of CD cases showed isolated increase of IELs in D1 without architectural modification.

CONCLUSIONS

D1 allowed diagnosis of CD in 21% of cases and IEL >70 per 100 EC correlated strongly with CD. Between 40 and 70 IELs per 100 EC, CD is very likely but other DD must be considered. Finally, the preferential localisation of IELs above EC nuclei favours CD, and increased IEL in D1 may be the sole abnormality.

The Role of T-Cell Subsets in Chronic Inflammation in Celiac Disease and Inflammatory Bowel Disease Patients: More Common Mechanisms or More Differences?

Background

Chronic intestinal inflammation due to noninfectious causes represents a growing health issue all over the world. Celiac disease as well as inflammatory bowel diseases (IBD) like Crohn's disease and ulcerative and microscopic colitis involve uncontrolled T-cell activation and T-cell-mediated damage as common denominators. Therefore, diagnosis and treatment decisions clearly benefit from the knowledge of the intricacies of the systemic and the local T-cell activity.

Summary

Depending on the cytokine milieu, CD4⁺ T cells can differentiate into proinflammatory T helper 1 (Th1), anti-inflammatory Th2, antimicrobial Th17, pleiotropic Th9, tissue-instructing Th22 cells, and in the regulatory compartment forkhead box protein 3⁺ Treg, suppressive Tr1 or Th3 cells. Additionally, follicular Th cells provide B-cell help in antibody class switching; cytotoxic CD8⁺ T cells target virus-infected or tumor cells. This review discusses our current knowledge on the contribution of defined T-cell subpopulations to establishing and maintaining chronic intestinal inflammation in either of the above entities. It also puts emphasis on the differences in the prevalence of these diseases between Eastern and Western countries.

Key Messages

In celiac disease, the driving role of T cells in the lamina propria and in the epithelium mainly specific for two defined antigens is well established. Differences in genetics and lifestyle between Western and Eastern countries were instrumental in understanding underlying mechanisms. In IBD, the vast amount of potential antigens and the corresponding antigen-specific T cells makes it unlikely to find universal triggers. Increased mucosal CD4⁺ regulatory T cells in all four entities fail to control or abrogate local inflammatory processes. Thus, prevailing differences in the functional T-cell subtypes driving chronic intestinal inflammation in celiac disease and IBD at best allow some overlap in the treatment options for either disease.

Pathological and Clinical Correlation between Celiac Disease and Helicobacter Pylori Infection; a Review of Controversial Reports

There are overwhelming reports and descriptions about celiac associated disorders. Although there is a clear genetic association between celiac disease (CD) and some gastrointestinal disorders, there are controversial reports claiming an association between CD and Helicobacter pylori (H. pylori) infection. Different studies indicated the possible association between lymphocytic gastritis and both CD and H. pylori infection, although this evidence is not consistently accepted. Also it was shown that an increase in intraepithelial lymphocytes count is associated with both H. pylori infection and celiac disease. Therefore the following questions may raise: how far is this infection actually related to CD?, which are the underlying patho-mechanisms for these associations? what are the clinical implications? what is the management? and what would be the role of gluten free diet in treating these conditions? PubMed (PubMed Central), Ovid, ISI of web knowledge, and Google scholar were searched for full text articles published between 1985 and 2015. The associated keywords were used, and papers described particularly the impact of pathological and clinical correlation between CD and H. pylori infection were identified. In this review we tried to answer the above questions and discussed some of the recent developments in the pathological and clinical aspects of CD and H. pylori infection.

CD3 immunohistochemical staining in diagnosis of lymphocytic colitis

Microscopic colitis (MC) is a common cause of chronic watery diarrhea. Traditionally, MC encompasses the 2 subgroups lymphocytic colitis (LC) and collagenous colitis, but recently, an additional subgroup, MC incomplete, has been introduced. Distinguishing between the subgroups relies exclusively on histopathologic evaluation. In the present study, 4 pathologists evaluated 156 archived biopsies originally diagnosed as LC or LC incomplete (LCi). Each pathologist assigned a diagnosis of LC, LCi, or nonspecific inflammation to all cases at 2 independent assessments. At the first assessment, hematoxylin and eosin (HE) stainings were available. At the second assessment, a supplementary CD3 immunohistochemical staining was also available. The aim was to evaluate whether a supplementary CD3 would increase the diagnostic agreement among pathologists, and whether a CD3 stain would change the diagnosis based on HE staining only. After the complete assessment, the cases were divided into 3 groups, that is, full agreement, partial agreement, and disagreement. The CD3 staining increased the number of cases with full agreement from 60 to 78. One hundred thirty-one cases with agreement or partial diagnostic agreement based on HE + CD3 were compared with the HE diagnoses. In 44 (34%) of 131 cases, CD3 changed the diagnosis. Cases assigned to the LCi category based on HE were often changed by a supplementary CD3. Conclusively, it is recommended to use a CD3 before giving the histopathologic diagnosis of LCi.

Inverse Association Between Helicobacter pylori Gastritis and Microscopic Colitis

BACKGROUND

Inflammatory bowel disease is known to be inversely associated with Helicobacter pylori infection of the upper gastrointestinal tract. We hypothesized that a similar inverse association also applied to microscopic colitis.

METHODS

The associations between microscopic colitis and presence of H. pylori-positive chronic active gastritis (CAG), H. pylori-negative CAG, intestinal metaplasia, or gastric atrophy were expressed as odds ratios with their 95% confidence intervals. Multivariate logistic regression analyses were used to adjust these associations for sex, age, percentage residents per ZIP code with white, black, Hispanic, or Asian ethnicity, percentage with college education, average housing values, annual income, and population size of individual ZIP codes.

RESULTS

H. pylori-positive CAG was less common among patients with than without microscopic colitis (odds ratio = 0.61; 95% confidence interval, 0.52-0.70). Intestinal metaplasia also occurred less frequently among patients with than without microscopic colitis (0.75, 0.65-0.86). These inverse associations remained unaffected by adjustments for parameters of ethnicity and socioeconomic status. In contradistinction with H. pylori-positive CAG, H. pylori-negative CAG was more common in patients with than without microscopic colitis (1.54, 1.17-1.97).

CONCLUSIONS

H. pylori infection and microscopic colitis are inversely associated. This observation is consistent with similar inverse associations found between H. pylori and inflammatory bowel disease. These relationships may provide clues about the yet unknown etiology of microscopic colitis.

The coeliac stomach: gastritis in patients with coeliac disease

BACKGROUND

Lymphocytic gastritis (LG) is an uncommon entity with varying symptoms and endoscopic appearances. This condition, as well as two forms of H. pylori-negative gastritis [chronic active gastritis (CAG) and chronic inactive gastritis (CIG)], appears to be more common in patients with coeliac disease (CD) based on single-centred studies.

AIM

To compare the prevalence of LG, CAG and CIG among those with normal duodenal histology (or nonspecific duodenitis) and those with CD, as defined by villous atrophy (Marsh 3).

METHODS

We analysed all concurrent gastric and duodenal biopsy specimens submitted to a national pathology laboratory during a 6-year period. We performed multiple logistic regression to identify independent predictors of each gastritis subtype.

RESULTS

Among patients who underwent concurrent gastric and duodenal biopsy (n = 287,503), the mean age was 52 and the majority (67%) were female. Compared to patients with normal duodenal histology, LG was more common in partial villous atrophy (OR: 37.66; 95% CI: 30.16-47.03), and subtotal/total villous atrophy (OR: 78.57; 95% CI: 65.37-94.44). CD was also more common in CAG (OR for partial villous atrophy 1.93; 95% CI: 1.49-2.51, OR for subtotal/total villous atrophy 2.42; 95% CI: 1.90-3.09) and was similarly associated with CIG (OR for partial villous atrophy 2.04; 95% CI: 1.76-2.35, OR for subtotal/total villous atrophy 2.96; 95% CI: 2.60-3.38).

CONCLUSIONS

Lymphocytic gastritis is strongly associated with coeliac disease, with increasing prevalence correlating with more advanced villous atrophy. Chronic active gastritis and chronic inactive gastritis are also significantly associated with coeliac disease. Future research should measure the natural history of these conditions after treatment with a gluten-free diet.

Low Prevalence of Colon Polyps in Chronic Inflammatory Conditions of the Colon

OBJECTIVES

Previous studies have reported a low prevalence of colon polyps in patients with microscopic colitis. The aim of the study was to test whether such inverse associations applied to other inflammatory diseases of the colon.

METHODS

In a case-control study among 130,204 patients undergoing colonoscopy for the work-up of diarrhea, we compared the prevalence of colon polyps in a case population of patients with inflammatory bowel disease (IBD), microscopic colitis, histologic signs of active colitis, diverticulitis, or ischemic colitis, and in a control population with normal colon mucosa. Case and control subjects were compared using odds ratios and their 95% confidence intervals adjusted for age and sex.

RESULTS

In 11,176 patients with microscopic colitis, the prevalence of hyperplastic polyps, serrated adenomas, and tubular adenomas were all reduced: odds ratios=0.46 (95% confidence intervals=0.43-0.49), 0.24 (0.19-0.30), and 0.35 (0.33-0.38), respectively. In 4,435 patients with IBD, the corresponding values were: 0.18 (0.15-0.21), 0.24 (0.16-0.35), and 0.18 (0.15-0.21), respectively. In 6,501 patients with histologically active colitis, the corresponding values were: 0.58 (0.53-0.63), 0.57 (0.46-0.70), and 0.63 (0.58-0.68), respectively. No such consistent reduction in polyp prevalence was found in patients with diverticulitis or ischemic colitis.

CONCLUSIONS

Chronic inflammatory conditions of the colon are associated with a decreased prevalence of colon polyps.

Microscopic colitis

Microscopic colitis (MC) is the common denominator for lymphocytic and collagenous colitis (CC). It is now recognized as a relatively frequent cause of diarrhea that equals the prevalence of inflammatory bowel disease. Patients are typically middle-aged women, but disease may occur at every age. Patients with MC report watery, non-bloody diarrhea in the absence of endoscopic and radiologic abnormalities. Lymphocytic colitis is characterized by an increased number of intraepithelial lymphocytes, and CC by a thickened subepithelial collagen band, whereas in both an increased mononuclear infiltration of the lamina propria is found. The pathogenesis of MC is largely unknown, but may relate to autoimmunity, adverse reactions to drugs or (bacterial) toxins, and abnormal collagen metabolism in the case of CC. Budesonide is so far the only drug that has proven efficacy in randomized controlled trials both for the induction and maintenance of remission. Patients who are nonresponsive, dependent or who experience side effects on budesonide may benefit from thiopurine or anti-TNF treatment, but these options are still experimental. The long-term prognosis of MC is good; it does not appear to predispose to malignancies and can in some cases be self-limiting. Further research and randomized clinical trials are required to expand our understanding of the natural course and the pathogenesis of MC.