Gastrointestinal pathology in patients with common variable immunodeficiency and X-linked agammaglobulinemia

Navigating the Complexities of Common Variable Immunodeficiency Enteropathy: From Established Therapies to Emerging Interventions

Common Variable Immunodeficiency (CVID) is a prevalent primary immunodeficiency in adults, marked by low immunoglobulin levels and recurrent infections. This review examines the gastrointestinal complications of CVID, including both infectious and non-infectious manifestations. It highlights therapeutic strategies, from antimicrobials to novel biologics, and the role of immune modulation. The review also explores the impact of gut microbiota dysbiosis on CVID pathogenesis and emphasizes the need for personalized treatment approaches and routine cancer screening due to the elevated risk of gastrointestinal malignancy in CVID patients.

The Histologic Spectrum of Rituximab-Associated Common Variable Immunodeficiency-Like Enteropathy

Rituximab (RTX) is a monoclonal anti-CD20 antibody widely used to treat B-cell neoplasms and autoimmune conditions. RTX has recently been linked to an enteropathy characterized by diarrhea, malabsorption, and hypogammaglobulinemia, closely resembling common variable immunodeficiency (CVID) enteropathy. We present the first dedicated histopathologic assessment of RTX-associated CVID-like enteropathy. Study inclusion criteria were the presence of diarrhea, weight loss, or other gastrointestinal symptoms in the setting of current/prior RTX use and associated hypogammaglobulinemia. Twenty-two patients (15 male:7 female; mean age at biopsy/resection, 63.4 years) across 9 tertiary medical centers met inclusion criteria and had small bowel (N = 20) and/or colon (N = 17) specimens (biopsies/resections) available for review; 71.4% of specimens dated from ≤5 years of last RTX dose. Cases were systematically evaluated by gastrointestinal pathologists at each institution. Key histologic features in the small bowel included sparse/absent lamina propria plasma cells (N = 10; 50%), intraepithelial lymphocytosis (N = 12; 60%), villous atrophy (N = 11; 55%), increased crypt apoptotic bodies (N = 6; 30%), and active inflammation (N = 5; 25%). Common features in the colon included sparse/absent plasma cells (N = 7; 41.2%), increased crypt apoptotic bodies (N = 7; 41.2%), active inflammation (N = 5; 29.4%), and intraepithelial lymphocytosis (N = 4; 23.5%). Goblet cell loss was appreciated in small bowel and/or colon specimens from 2 patients. Follow-up biopsies (interval, 2 months to 4 years) were available for 7 patients and largely recapitulated the histology of the index specimens, though 1 patient demonstrated improvement in villous blunting and intraepithelial lymphocytosis. In summary, the histologic spectrum of post-RTX CVID-like enteropathy encompasses lamina propria plasma cell depletion, increased crypt apoptotic bodies, small bowel villous atrophy, and goblet cell loss. While the underlying pathophysiology remains uncertain, the clinicopathologic picture may reflect post-RTX B-cell/plasma cell impairment. Although histologic findings may be subtle and variable, pathologists should be aware of this entity and should seek a history of RTX use in patients whose biopsies exhibit these CVID enteropathy-like features.

Chimeric antigen receptor (CAR) T-cell therapy-related gastrointestinal toxicity: Histologic features and morphologic mimics

Chimeric antigen receptor (CAR) T-cell therapy is a contemporary treatment modality for hematologic malignancies, with potential future applications in solid tumors. While the clinical side effects of CAR T-cell therapy are well-documented, histologic correlations of gastrointestinal (GI) toxicity remain underreported. This study prospectively identified 5 sets of GI biopsies from 3 patients presenting with CAR T-cell therapy-associated GI toxicity. Patients exhibited symptoms such as abdominal pain, hematochezia, non-bloody diarrhea, weight loss, and fever/chills, occurring 1.5-8 months post-therapy. Histologic examination revealed a graft versus host disease (GVHD)-like pattern of injury in colon biopsies, characterized by epithelial apoptosis, crypt dropout, and neuroendocrine cell nests. One duodenal biopsy showed intraepithelial lymphocytosis and villous blunting, mimicking celiac disease. A notable paucity of CD20-positive B-cells and CD38-positive plasma cells was observed in both colonic and small intestinal biopsies. Two patients required biologic agents for treatment, while one patient improved with corticosteroids but succumbed to an upper respiratory infection. The findings underscore the necessity of correlating symptom onset with therapy timing to achieve accurate diagnosis of CAR T-cell therapy-associated GI toxicity.

Gastrointestinal pathology in Good's syndrome, thinking beyond common variable immunodeficiency: a clinicopathological observation

Good's syndrome (GS) is a rare immunodeficiency associated with thymoma, characterized by increased susceptibility to bacterial, viral, and fungal infections, along with autoimmune manifestations. Gastrointestinal symptoms are common in GS, yet its clinical and histopathological features remain underrecognized. Due to significant overlap in clinical presentation and immunological profiles, GS is frequently misdiagnosed as common variable immunodeficiency (CVID). While gastrointestinal pathology in CVID has been well-documented, data on gastrointestinal manifestations in GS are limited. In this study, we analyzed two cases of GS, both demonstrating marked reduction of plasma cells across multiple gastrointestinal sites, with variable intraepithelial lymphocytosis and mild to moderate villous blunting in the duodenum and features secondary to chronic norovirus infection in one case, and an invasive adenocarcinoma with notable depletion of lamina propria plasma cells in the other. Accurate recognition of GS is essential for pathologists and clinicians, given its poorer prognosis compared to CVID.

T-cells are significantly reduced in the luminal gastrointestinal tract of patients with "complete" 22q11.2 deletion syndrome (DiGeorge syndrome): Utilization of chromogenic multiplex immunohistochemistry to define cellular populations

Patients with 22q11.2 deletion syndrome or DiGeorge syndrome commonly report gastrointestinal symptoms in addition to more widely understood cardiac and immunodeficiency abnormalities. However, the morphologic features of gastrointestinal tract pathology in these patients are poorly understood. We previously reported that plasma cells are essentially absent from the luminal gastrointestinal tract of patients with "complete" DiGeorge syndrome. Herein, we add to the current understanding of the luminal gastrointestinal tract changes in patients with DiGeorge syndrome. Patients with cytogenetically confirmed DiGeorge syndrome were identified after approval from our institutional review board. Gastrointestinal tract biopsies from patients with DiGeorge syndrome that were severely immunosuppressed (complete DiGeorge syndrome, DGS-I), partially immunocompromised (partial DiGeorge syndrome, DGS), and from control patients were reviewed. Two panels of chromogenic multiplex immunohistochemistry (IHC) were performed to evaluate the immune cell infiltrate in the lamina propria of the duodenum and colon. "Panel #1" was composed of antibodies targeting CD3, CD20, and CD68. "Panel #2" was composed of antibodies targeting CD4, CD8, CD56, and TCRϒδ. Assessment of cell types identified by these antibody targets demonstrated a significant reduction of duodenal and colonic T-cells in patients with complete DiGeorge syndrome. In addition to establishing the morphologic phenotype of the luminal gastrointestinal tract of patients with DiGeorge syndrome, we also highlight our chosen technology of chromogenic multiplex IHC as a relatively accessible research and diagnostic tool with wide potential to be utilized across various disease processes.

Gastrointestinal Disease in Common Variable Immunodeficiency Disorder (CVID): Histological Patterns, Diagnostic Clues and Pitfalls for the Pathologist and Gastroenterologist

Background/Objectives: Gastrointestinal diseases are a major cause of morbidity in common variable immunodeficiency disorder (CVID), clinically often mimicking other conditions including celiac disease and inflammatory bowel disease (IBD). Hence, diagnosis of CVID remains challenging. This study aims to raise awareness and highlight histopathological clues for CVID in intestinal biopsies, emphasizing diagnostic pitfalls for the pathologist/gastroenterologist. Methods: We reviewed 63 (18 duodenal, 23 ileal, 22 colonic) biopsies and case histories from seven CVID patients, obtained over a 31-year period, with attention to active inflammation, intraepithelial lymphocytes, plasma cells, lymphoid hyperplasia, crypt/villous architecture, subepithelial collagen, apoptosis, granulomas, and infections. Clinical information of 41 pathology requests was reviewed. Results: Gastrointestinal symptoms were variable. Histological features included IBD-like (3/7), celiac disease-like (2/7), graft-versus-host disease (GVHD)-like (2/7), lymphocytic sprue/colitis-like (3/7), collagenous colitis-like (2/7), and acute colitis-like (4/7) patterns, often overlapping (2/7) and/or changing over time (3/7). Lymphoid hyperplasia was seen in 3/7 patients; 1/7 had giardiasis; and 5/7 had few plasma cells, usually only in part of the gut (3/5). Clinical information of 12/41 (29%) pathology requests mentioned known/suspected CVID, despite being known in 33/41 (80%). Conclusions: Clinical/histological features of CVID in the gut are diverse, often mimicking IBD, microscopic colitis, celiac disease and/or GVHD, hence the importance of adequate clinical information. Some histological features are atypical of these established entities and may indicate CVID, as may overlapping/changing histological patterns and/or few plasma cells in part of the gut. Awareness of the heterogenous clinical presentation and histopathological indicators of CVID may improve diagnosis.

The Natural History of Inflammatory Bowel Disease in Adults With Common Variable Immunodeficiency: A Case Series From a Single US Tertiary Care Center

Background

Common variable immunodeficiency (CVID) predisposes patients to inflammatory bowel disease (IBD). There are limited studies characterizing adults with concomitant CVID and IBD (CVID-IBD).

Methods

Demographics, clinical courses, endoscopic findings, and disease-specific therapies were obtained in adults ≥18 years with CVID-IBD over a 5-year period.

Results

We identified 11 patients with CVID-IBD, 6 with Crohn's disease (CD), and 5 with ulcerative colitis (UC). The presenting symptoms in 10 (91%) were abdominal pain and diarrhea. A majority of patients were diagnosed with IBD before CVID. Patients with CVID-IBD were diagnosed with CVID at an older age compared to patients with CVID only. The most prevalent endoscopic finding in CD was either erythema or erosions in the ileum, whereas in UC, it was pancolitis. One patient with CD and 1 with UC required treatment with immunomodulators to achieve remission. Three patients with CD and 2 with UC required treatment with biologics to achieve remission. Eight received intravenous immunoglobulin (IVIG) for CVID. Four patients with CD and 1 with UC were diagnosed with either leukemia or lymphoma, and the most common malignancy was chronic lymphocytic leukemia (n = 3).

Conclusions

This is one of few studies evaluating demographic, clinical, endoscopic, histologic features, and therapeutic management in patients with CVID-IBD. Further studies are required to elucidate long-term differences in the clinical course and treatment of patients with CVID-IBD.

Paucity of gastrointestinal plasma cells in common variable immunodeficiency

PURPOSE OF REVIEW

Common variable immunodeficiency enteropathy (CVID-E) is a noninfectious complication of CVID caused by chronic inflammation of the gastrointestinal (GI) tract. Based on literature, a paucity or lack of plasma cells, although not obligatory for diagnosis, is a pathognomonic feature of CVID and more frequent in CVID-E. However, there is no consensus on standardized histopathological analysis of this feature in biopsies. In this systematic review, we highlight methods of reproducible plasma cell quantification of biopsies in CVID and describe the plasma cell counts and classes as presented in the literature.

RECENT FINDINGS

Reduced plasma cell counts are commonly found over the entire GI tract, except for in the oesophagus. Immunoglobulin A+ (IgA+) plasma cells appear to be the most commonly reduced plasma cell class in CVID, yet there is scarce literature on the predictive value of low IgA+ plasma cell counts in CVID-E.

SUMMARY

We propose two optimized methodologies of quantification using a cut-of value of <10 plasma cells per HPF at 40× magnification, or a proportion of ≥1-5% of total mononuclear cells, recorded over ≥3 sections, and in ≥2 biopsies, as the most conservative agreeable definitions for a paucity of plasma cells to be used in diagnostics and further research.

Endoscopic characterization of gastrointestinal manifestations in children with undifferentiated recurrent fever

BACKGROUND AND STUDY AIMS

Systemic autoinflammatory diseases are characterized by recurrent or chronic inflammation, and monogenic forms are increasingly defined. However, a group of patients without genetic diagnosis is called the syndrome of undifferentiated recurrent fever (SURF). This study analyzed the clinical and endoscopic features of patients with SURF presenting with gastrointestinal (GI) symptoms.

PATIENTS AND METHODS

Between 2019 and 2022, GI endoscopy were performed in patients with SURF who presented with GI symptoms. Clinical, genetic, laboratory, and endoscopy findings were analyzed.

RESULTS

Fifteen patients were included in the study, eight (53.3 %) were girls. The mean age was 10.5 ± 5.80 years, and the median age at symptom onset was 4 (0.3-16) years. All patients experienced fever and abdominal pain. Thirteen patients (86.7 %) experienced diarrhea, 11 (73.3 %) reported myalgia, and 10 (66.7 %) had joint involvement. Lymphoid follicles in the terminal ileum mucosa were detected in 10 patients (66.7 %), and nodular lymphoid hyperplasia in the terminal ileum was the histopathological finding in 12 patients (80 %).

CONCLUSIONS

The current study found that patients with SURF experiencing gastrointestinal symptoms have excessive lymph node formation in the terminal ileal mucosa due to an exaggerated inflammatory response. This may be the cause of their GI symptoms.

CVID-Associated Intestinal Disorders in the USIDNET Registry: An Analysis of Disease Manifestations, Functional Status, Comorbidities, and Treatment

Common variable immunodeficiency (CVID) has been subdivided into five phenotypes, including one marked by non-infectious enteropathies that lead to significant morbidity and mortality. We examined a large national registry of patients with CVID to better characterize this population and understand how the presence of enteropathy influences nutritional status, patient function, and the risk of additional non-infectious disorders in CVID patients. We also sought to illustrate the range of treatment strategies for CVID-associated enteropathies. We extracted patient data from the United States Immunodeficiency Network (USIDNET) database, which included 1415 patients with CVID, and compared those with and without intestinal disorders. Demographic and genetic profiles, functional status, and treatments targeting intestinal disorders are reported. Intestinal disorders were present in 20% of patients with CVID, including chronic diarrhea, inflammatory bowel disease, malabsorption, and others. Compared to those without enteropathies, this patient subset exhibited significantly lower Karnofsky-Lansky functional scores, greater reliance on nutritional support, higher rates of vitamin deficiencies, and increased prevalence of hematologic disorders, liver disease, pulmonary disease, granulomatous disease, and lymphoma. Genetic data were reported for only 5% of the cohort. No mutations segregated significantly to patients with or without intestinal disease. Corticosteroids were most frequently used for treatment. Patients with CVID-associated intestinal disorders exhibit higher rates of autoimmune and inflammatory comorbidities, lymphoma, malnutrition, and debility. We review recent studies implicating specific pathways underlying this immune dysregulation. Further studies are needed to evaluate the role of targeted immunomodulatory therapies for CVID-associated intestinal disorders.

Gut inflammation and tumorigenesis: every site has a different tale to tell

Gut inflammation has been correlated with cancerogenesis by disrupting gastrointestinal homeostasis. Numerous chronic inflammatory disorders of the tubular gastrointestinal tract (e.g., gastroesophageal reflux disease, Helicobacter pylori-induced and autoimmune chronic gastritis, celiac disease, and inflammatory bowel diseases) have been variably associated with an increased neoplastic risk. Gastrointestinal inflammation-induced neoplasms include epithelial tumors (esophageal squamous cell carcinoma and adenocarcinoma, gastric adenocarcinoma and neuroendocrine tumors, small bowel adenocarcinoma and neuroendocrine tumors, and colorectal cancer) and lymphomas (such as gastric marginal zone lymphomas and enteropathy-associated T cell lymphoma). In the last decades, numerous studies have investigated the pathogenetic mechanisms and the microenvironmental/microbiome changes that trigger genetic and/or epigenetic alterations eventually leading to tumorigenesis, often through a histologically recognizable inflammation-dysplasia-carcinoma cancerogenic sequence. In the present review, an overview of the current knowledge on the links between inflammatory diseases and neoplasms of the tubular GI tract, applying a site-by-site approach, is provided.

Fresh-Frozen Plasma as a Low-Cost Replacement of Intravenous Immunoglobulin for the Treatment of Symptomatic Hypogammaglobulinemia

Hypogammaglobulinemia commonly presents with chronic diarrhea. Unfortunately, these patients require intravenous immunoglobulin (IVIG) transfusions of 400-800 mg/kg every 3-4 weeks as a standard treatment for hypogammaglobulinemia. Repeated transfusion of IVIG is costly, and many patients may not be able to afford it. We report the case of a young male with chronic small intestinal diarrhea who was later diagnosed with hypogammaglobulinemia. We treated the patient with fresh-frozen plasma (FFP) and the patient responded favorably. FFP transfusion may be an affordable alternative to IVIG in the treatment of hypogammaglobulinemia.

CVID-associated intestinal disorders in the USIDNET registry: An analysis of disease manifestations, functional status, comorbidities, and treatment

Common variable immunodeficiency (CVID) has been subdivided into five phenotypes, including one marked by non-infectious enteropathies that lead to significant morbidity and mortality. We examined a large national registry of patients with CVID to better characterize this population and understand how the presence of enteropathy influences nutritional status, patient function, and the risk of additional non-infectious disorders in CVID patients. We also sought to illustrate the range of treatment strategies for CVID-associated enteropathies. We extracted patient data from the United States Immunodeficiency Network (USIDNET) database, which included 1415 patients with CVID, and compared those with and without intestinal disorders. Demographic and genetic profiles, functional status, and treatments targeting intestinal disorders are reported. Intestinal disorders were present in 20% of patients with CVID, including chronic diarrhea, inflammatory bowel disease, malabsorption, and others. Compared to those without enteropathies, this patient subset exhibited significantly lower Karnofsky-Lansky functional scores, greater reliance on nutritional support, higher rates of vitamin deficiencies, and increased prevalence of hematologic disorders, liver disease, pulmonary disease, granulomatous disease, and lymphoma. Genetic data were reported for only 5% of the cohort. No mutations segregated significantly to patients with or without intestinal disease. Corticosteroids were most frequently used for treatment. Patients with CVID-associated intestinal disorders exhibit higher rates of autoimmune and inflammatory comorbidities, lymphoma, malnutrition, and debility. We review recent studies implicating specific pathways underlying this immune dysregulation. Further studies are needed to evaluate the role of targeted immunomodulatory therapies for CVID-associated intestinal disorders.

An Expert Opinion/Approach: Clinical Presentations, Diagnostic Considerations, and Therapeutic Options for Gastrointestinal Manifestations of Common Variable Immune Deficiency

Common variable immunodeficiency (CVID) is the most common symptomatic primary immunodeficiency. It is characterized by impaired B-cell differentiation. Although patients can be diagnosed with CVID anytime during their lifetime, most patients have symptoms for 5-9 years before their diagnosis. The diagnosis of CVID starts with a detailed history focusing on the infectious and noninfectious manifestations of the disease. In patients who are suspected to experience CVID, quantitative immunoglobulins (Ig) should be checked to confirm the diagnosis. IgG should be at least 2 times less than the age-specific SD along with either a low IgA or IgM and with evidence of impaired vaccine response. CVID is usually associated with infectious and/or noninfectious conditions, the latter of which can be inflammatory, autoimmune, lymphoproliferative, or malignant, among other manifestations. Ig therapy has positively affected the disease course of patients with infectious complications but has limited effect on the noninfectious manifestations because the noninfectious complications are related to immune dysregulation involving B cells and T cells rather than primarily due to antibody deficiency. When the gastrointestinal (GI) system is involved, patients with CVID may display signs and symptoms that mimic several GI conditions such as celiac disease, pernicious anemia, or inflammatory bowel diseases. The inflammatory bowel disease-like condition is usually treated with steroids, 5-aminosalicylates, thiopurines, or biologic agents to control the inflammation. In this review, the clinical presentations, diagnostic considerations, and therapeutic options for GI manifestations of CVID will be discussed to facilitate the individualized management of these often-complex patients.

Malabsorption Syndromes and Food Intolerance

Feeding intolerance is ubiquitous in neonatal intensive care units with as many signs and symptoms as possible diagnoses. Optimizing nutrition is paramount in both preterm and term infants. Determining the cause of feeding intolerance and adjusting nutrition interventions is an important part of the daily care of newborns. This review discusses the role of malabsorption and food intolerance as possible causes of nutrition difficulties in the newborn.

ECCO Topical Review on Clinicopathological Spectrum and Differential Diagnosis of Inflammatory Bowel Disease

INTRODUCTION

Many diseases can imitate inflammatory bowel disease [IBD] clinically and pathologically. This review outlines the differential diagnosis of IBD and discusses morphological pointers and ancillary techniques that assist with the distinction between IBD and its mimics.

METHODS

European Crohn's and Colitis Organisation [ECCO] Topical Reviews are the result of an expert consensus. For this review, ECCO announced an open call to its members and formed three working groups [WGs] to study clinical aspects, pathological considerations, and the value of ancillary techniques. All WGs performed a systematic literature search.

RESULTS

Each WG produced a draft text and drew up provisional Current Practice Position [CPP] statements that highlighted the most important conclusions. Discussions and a preliminary voting round took place, with subsequent revision of CPP statements and text and a further meeting to agree on final statements.

CONCLUSIONS

Clinicians and pathologists encounter a wide variety of mimics of IBD, including infection, drug-induced disease, vascular disorders, diverticular disease, diversion proctocolitis, radiation damage, and immune disorders. Reliable distinction requires a multidisciplinary approach.

Primary Hypogammaglobulinaemia with Inflammatory Bowel Disease-Like Features: An ECCO CONFER Multicentre Case Series

BACKGROUND

Hypogammaglobulinaemia is a disorder characterized by low serum immunoglobulin levels and a high prevalence of gastrointestinal manifestations. In some cases, clinical and endoscopic features are indistinguishable from those of inflammatory bowel disease [IBD].

METHODS

This was a multicentre case series performed as a part of the European Crohn's and Colitis Organisation [ECCO] Collaborative Network of Exceptionally Rare case reports [CONFER] project.

RESULTS

This report includes 27 patients with primary hypogammaglobulinaemia and IBD-like features: 20 males and seven females, median age 45.6 years (interquartile range [IQR] 35.2-59). Crohn's disease-like features were noted in 23 patients, and four patients had ulcerative colitis-like features. The diagnosis of hypogammaglobulinaemia preceded a diagnosis of IBD-like features in 20 patients [median of 7 years prior, IQR 2.6-20.6 years], and followed the appearance of IBD-like features in seven cases [median of 1 year after, IQR 0.45-5.6 years]. Hypogammaglobulinaemia aetiologies were common variable immunodeficiency [66.6%], agammaglobulinaemia [7.4%], selective IgA-deficiency [11.1%], Good's syndrome [7.4%], IgG subclass deficiency with IgA deficiency [3.7%] and hyper-IgM [3.7%]. In addition to antibiotics and intravenous immunoglobulin [IVIG] for hypogammaglobulinaemia, 12 patients received IBD-related treatment including 5-aminosalicylate agents [two patients], corticosteroids [one patient], thiopurines [three patients], anti-tumour necrosis factor [four patients] and vedolizumab [two patients]. By the end of the follow-up (44.5 months [IQR 18-81]), 21/27 [77%] patients were in clinical remission.

CONCLUSION

This case series describes IBD-like features in patients with hypogammaglobulinaemia. The diagnosis of IBD-like features mainly occurred after that of hypogammaglobulinaemia, with successful recovery in the majority of cases after appropriate treatment.

The Diagnosis of Common Variable Immunodeficiency After Multisystem Dysfunction

Common variable immunodeficiency (CVID) is a primary immunodeficiency caused by the lack of B cell differentiation into plasma cells, thereby leading to decreased serum immunoglobulins. Patients with this condition are predisposed to recurrent infections and are more likely to develop certain cancers and autoimmune diseases. We report the case of a 53-year-old female suffering from recurrent pulmonary infections and a history of non-Hodgkin lymphoma (NHL) who had a poor response to the measles, mumps, and rubella (MMR) and varicella vaccines as a child, and was infected with coronavirus disease 2019 (COVID-19) twice in 2020. Testing of her antibody titers in order to determine suitability for Streptococcus pneumoniae (S. pneumoniae) vaccination found an overall decrease in major immunoglobulin classes (IgG, IgM, and IgA) and B cells with normal morphology. The diagnosis of CVID was made, and prompt treatment with intravenous immunoglobulins (IVIG) brought her IgG levels up from 282 to 680 mg/dL within three months. This case highlights the importance for providers to keep immunological dysfunction on their differentials for patients with atypical presentations involving multiple organ systems.

Gut inflammation in CVID: causes and consequences

INTRODUCTION

There is a wide spectrum of noninfectious gastrointestinal pathology, causing considerable morbidity and mortality in CVID, where both etiology and effective therapy are under debate.

AREAS COVERED

This review will focus on the noninfectious inflammation in the GI tract in CVID patients, covering the both the upper and lower GI tract inflammation, including the liver. The controversy of the CVID enteropathy definition and that of gluten-free diet for celiac-like disease in CVID will be discussed. Furthermore, the review will cover the link between GI inflammation and GI cancer. Finally, the role of gut microbiota, IgA, and genetics and its relationship with CVID enteropathy is scrutinized. The authors reviewed literature from PubMed.

EXPERT OPINION

The heterogeneity and the unknown mechanism behind CVID enteropathy, and thereby the lack of effective treatment, is one of the key challenges in the field of CVID. Celiac-like disease in CVID is due to immune dysregulation, and a gluten-free diet is therefore not indicated. Gut microbial dysbiosis and mucosal IgA can initiate systemic and local inflammation and is involved in the immune dysregulation in CVID. Considering the heterogeneity of CVID enteropathy, personalized medicine is probably the future for these patients.

A Pattern-based Pathology Approach to Very Early-onset Inflammatory Bowel Disease: Thinking Beyond Crohn Disease and Ulcerative Colitis

Very early-onset inflammatory bowel disease (VEO-IBD), IBD diagnosed in children younger than 6 years old, is phenotypically and genetically distinct from older onset IBD. Monogenic and digenic causative defects, particularly in primary immunodeficiency and intestinal epithelial barrier genes, have been identified in a subset of patients with VEO-IBD allowing for targeted therapies and improved outcomes. However, these findings are the minority, thus strategies to correctly diagnose patients, including identification of specific histopathologic findings with correlating clinical and laboratory features may provide critical and necessary insight into mechanisms of disease pathogenesis and subsequent therapeutic options. In this article, we review the pathologic findings seen in patients with VEO-IBD and outline a pattern-based approach to diagnosis using examples from primary immunodeficiencies with gastrointestinal manifestations.

Common variable immunodeficiency disorders: What generalists should know

Primary immune deficiency disorders (PIDDs) are common and underdiagnosed. Predominant antibody deficiencies (PADs) are the most common type of immune deficiency and comprise 55% of the immune deficiencies diagnosed.^[1] Although immunoglobulin A (IgA) deficiency remains the most common type of PID, common variable immunodeficiency disorders remain the most common symptomatic PID for which medical therapy is sought.

Plasma cells are essentially absent in the luminal gastrointestinal tract of patients with "complete" 22q11.2 deletion syndrome (DiGeorge syndrome)

Gastrointestinal symptoms are commonly reported in patients with 22q11.2 deletion syndrome or DiGeorge syndrome (DGS) in addition to the dominant cardiac manifestations and immunodeficiency. But literature providing specific morphologic details of the gastrointestinal tract pathology is very limited. Here, we provide the first comprehensive morphologic description of the luminal gastrointestinal tract changes in patients with DGS. Cytogenetically confirmed DGS patients were identified, clinical and laboratory data were reviewed to determine the severity of immunodeficiency, and patients were stratified into mildly immunocompromised, that is, partial DiGeorge anomaly or severely immunosuppressed, that is, complete DiGeorge anomaly groups. Gastrointestinal tract biopsies from these patients were retrospectively reviewed and compared with those from controls without the history of DGS. Patients with immunosuppressed DGS showed a near complete absence of plasma cells in the stomach, duodenum, and colon lamina propria by hematoxylin and eosin evaluation. Immunohistochemistry for CD138 used to highlight plasma cells confirmed this finding. The notable absence of plasma cells adds to the existing knowledge of the pathophysiology underlying DGS and expands the differential diagnostic considerations for this finding, which has been previously described in common variable immunodeficiency. It also provides a useful morphologic marker observable by the readily accessible light microscopy. Second, patients with DGS showed a mild increase in epithelial cell apoptosis in their colon. This finding is significant because of its overlap with morphologic features of gastrointestinal graft versus host disease as thymus transplantation is being used as a treatment option for patients with complete DGS.

Histopathology of Celiac Disease. Position Statements of the Italian Group of Gastrointestinal Pathologists (GIPAD-SIAPEC)

Celiac Disease (CeD) is an immune-mediated inflammatory disorder of the small intestine, affecting genetically susceptible individuals when exposed to gluten. Small intestinal biopsy interpretation has been the “gold standard” for celiac disease (CeD) for over 50 years. Despite today’s availability of sensitive and specific serological tests, the histopathological features from mucosal biopsy play a key role in diagnosing when CeD is suspected. Such a diagnostic approach requires a multidisciplinary team to optimize both tissue sampling and interpretation via the interaction between the pathologist and the gastroenterologist. Pathologists of the Italian Group of Gastrointestinal Pathology (GIPAD-SIAPEC), together with a member (TR) of the Italian Society of Technicians (AITIC) and an expert gastroenterologist (CC), provide position statements as a practical tool for reading and interpreting the report.

Moreover, a position statement was formulated about the recently described condition known as Non-Celiac Gluten Sensitivity (NCGS). Within such a diagnostic setting, both the architectural abnormalities of the duodenal mucosa, namely glandular hyperplasia, and villous atrophy and the number of intraepithelial T-lymphocytes should be well highlighted. Ancillary tests such as anti-CD3 stain are useful for an accurate count of the intraepithelial T lymphocytes when CeD or NCGS is suspected. Moreover, anti-CD3 and anti-CD8 stains are recommended in patients not responding to the gluten-free diet (GFD) to confirm a diagnosis of Refractory Celiac Disease (RCeD). Diagnostic clues about the differential diagnosis of both CeD and RCeD have also been rendered.

Crohn's-like Enteritis in X-Linked Agammaglobulinemia: A Case Series and Systematic Review

BACKGROUND

X-linked agammaglobulinemia (XLA) is an inherited primary immunodeficiency that usually manifests clinically with recurrent sinopulmonary infections. Gastrointestinal manifestations are mostly driven by acute infections and disturbed mucosal immunity, but there is a notable prevalence of inflammatory bowel disease (IBD). Differentiating between XLA-associated enteritis, which can originate from recurrent infections, and IBD can be diagnostically and therapeutically challenging.

OBJECTIVE

This study presents a critical appraisal of the clinical, radiological, endoscopic, and histological features associated with XLA-associated Crohn disease (CD)-like enteritis.

METHODS

We report 3 cases and performed a systematic review of the literature describing the diagnoses and outcomes.

RESULTS

An XLA-related enteropathy presented in adolescence with an ileocolonic CD-like phenotype without perianal disease. Abdominal pain, noninfectious diarrhea, and weight loss were the most common symptoms. Imaging and endoscopic findings closely resemble CD. However, histologically, it presents without nodular lymphoid hyperplasia and only 2 studies reported the presence of granulomas. In addition, in XLA-associated enteritis, immunohistochemistry showed the absence or marked reduction in B cells and plasma cells.

CONCLUSIONS

An XLA-associated enteritis is a distinct pathological process that presents clinically in a manner similar to ileocolonic CD. It is important to evaluate for infectious diarrhea, which is common in XLA and can mimic IBD clinically. Complete multidisciplinary evaluation is, therefore, recommended for XLA patients with persistent gastrointestinal symptoms. Although more research is needed, therapeutic selection for XLA-associated enteritis is like that of IBD, and the possible risk of drug interactions and complications from increasing immunosuppression should be considered.

Gastrointestinal Disease in Patients with Common Variable Immunodeficiency: A Retrospective Observational Study

BACKGROUND

Gastrointestinal (GI) symptoms are common among patients with common variable immunodeficiency disorder (CVID) yet remain poorly understood.

AIMS

The aim of this study was to characterize the demographic, clinical, endoscopic and histologic features of patients with CVID and GI symptoms.

METHODS

We conducted a retrospective observational study of all patients with CVID at a large Canadian tertiary care centre between January 2000 and May 2018.

RESULTS

We included 95 patients with CVID. The mean age of patients at the time of CVID diagnosis was 38.2(±16.0). Fifty-three (56%) patients were female. Sixty-four (67%) patients had GI symptoms, with a mean age of onset for GI symptoms of 43.4(±15.1) years. The most common symptoms were bowel movement changes (n = 55 [58%]) and abdominal pain (n = 44 [46%]). Patients with GI symptoms were more likely to have anemia (n = 23 [36%] versus n = 3 [10%], P = 0.0129), iron deficiency (n = 16 [25%] versus n = 2 [7%], P = 0.0481), and have received GI antibiotics (n = 37 [58%] versus n = 0, P < 0.0001) and proton pump inhibitors for reflux (n = 24 [38%] versus n = 3 [10%], P = 0.0067). The most common GI infections were Giardia lamblia (n = 14 [15%]) and Clostridium difficile (n = 4 [4%]). Forty-three (45%) patients with GI symptoms underwent colonoscopy, esophagogastroduodenoscopy or both. The most common findings were inflammation, nodular lymphoid hyperplasia, reduced plasma cells and increased intraepithelial lymphocytes.

CONCLUSIONS

This is the largest study on CVID patients in a North American setting. The majority of patients experienced GI symptoms. Future studies should study response to treatment for GI disease among patients with CVID.

Primary Humoral Immune Deficiencies: Overlooked Mimickers of Chronic Immune-Mediated Gastrointestinal Diseases in Adults

In recent years, the incidence of immune-mediated gastrointestinal disorders, including celiac disease (CeD) and inflammatory bowel disease (IBD), is increasingly growing worldwide. This generates a need to elucidate the conditions that may compromise the diagnosis and treatment of such gastrointestinal disorders. It is well established that primary immunodeficiencies (PIDs) exhibit gastrointestinal manifestations and mimic other diseases, including CeD and IBD. PIDs are often considered pediatric ailments, whereas between 25 and 45% of PIDs are diagnosed in adults. The most common PIDs in adults are the selective immunoglobulin A deficiency (SIgAD) and the common variable immunodeficiency (CVID). A trend to autoimmunity occurs, while gastrointestinal disorders are common in both diseases. Besides, the occurrence of CeD and IBD in SIgAD/CVID patients is significantly higher than in the general population. However, some differences concerning diagnostics and management between enteropathy/colitis in PIDs, as compared to idiopathic forms of CeD/IBD, have been described. There is an ongoing discussion whether CeD and IBD in CVID patients should be considered a true CeD and IBD or just CeD-like and IBD-like diseases. This review addresses the current state of the art of the most common primary immunodeficiencies in adults and co-occurring CeD and IBD.

Gastrointestinal findings in 26 adults with common variable immunodeficiency: The fickle nature of the disease manifests in gastrointestinal biopsies

BACKGROUND/AIMS

The aim of the present study was to demonstrate the histopathological findings in gastrointestinal (GI) biopsies in adults with common variable immunodeficiency (CVID).

MATERIALS AND METHODS

A total of 172 GI biopsies of 26 patients with CVID obtained over a 16-year period were reevaluated. Findings were analyzed using descriptive analyzes and χ2 test.

RESULTS

Female-to-male ratio was 1.36. The median age at diagnosis was 36±13.94 (16-72) years. Chronic esophagitis was noted in 3 patients. The absence of plasma cells in the stomach, duodenum, and colon was observed in 16, 14, and 9 patients, respectively. Divergent results for the presence of plasma cells in concurrent stomach and duodenum samples were found in 11 (44%) patients. Nodular lymphoid hyperplasia (NLH) was notable in the duodenum (56%). The mean number of eosinophils in one high-power field was significantly higher in duodenal biopsies with NLH (27.21 vs. 14.37, p=0.002). Active inflammation was more prominent in the colon (91%) than in the stomach (65%) and duodenum (60%). Helicobacter pylori infection was found in 57.6%, including a case with persistent infection by the coccoid form. Celiac-like villous blunting and increased intraepithelial lymphocytes were seen in 40% and 24%, respectively. In addition, 23% had giardiasis associated with acute duodenitis and duodenal NLH (p<0.05).

CONCLUSION

CVID gastroenteropathy is a challenging entity, and due to the heterogeneity in the presence and distribution of plasma cells throughout the GI tract and diverse disease course, multiple concurrent biopsies may be needed for tissue diagnosis. Duodenal CVID may present with villous alterations and giardiasis, and NLH appears to be an important clue in the duodenum. The association between duodenal NLH and eosinophil infiltration deserves further investigation.

Differential regulation of claudin-2 and claudin-15 expression in children and adults with malabsorptive disease

Intestinal Na+-nutrient cotransport depends on claudin-2 and claudin-15 mediated Na+ recycling. Expression of these proteins is coordinately regulated during postnatal development. While expression of claudin-2 and claudin-15 has been studied in inflammatory bowel disease (IBD) and celiac disease (CD), it has not been assessed in other malabsorptive diseases, and no reports have compared expression in children and adults. We used quantitative immunofluorescence microscopy to assess claudin-2 and claudin-15 expression in duodenal biopsies from children and adults with malabsorptive disease and healthy controls. Consistent with previous work in rodents, claudin-2 expression in healthy children was markedly greater, and claudin-15 expression was less, than that in adults. Claudin-2 expression was increased in adults with CD and downregulated in children with graft-versus-host disease (GVHD). In contrast, claudin-15 expression was reduced in adults with GVHD and common variable immunodeficiency (CVID). These data show that one of the two Na+/water pore-forming claudins is upregulated in CD and downregulated in GVHD and CVID. The specific claudin whose expression changes, however, reflects the age of the patient (child or adult). We conclude that contributions of claudin-2 and claudin-15 to pathophysiology of and responses to diarrhea in children and adults with GVHD and CVID differ from those in CD and IBD.

Heterogeneity of Liver Disease in Common Variable Immunodeficiency Disorders

Common variable immunodeficiency (CVID) is the most frequent primary immunodeficiency (PID) in adulthood and is characterized by severe reduction of immunoglobulin serum levels and impaired antibody production in response to vaccines and pathogens. Beyond the susceptibility to infections, CVID encompasses a wide spectrum of clinical manifestations related to a complex immune dysregulation that also affects liver. Although about 50% CVID patients present persistently deranged liver function, burden, and nature of liver involvement have not been systematically investigated in most cohort studies published in the last decades. Therefore, the prevalence of liver disease in CVID widely varies depending on the study design and the sampling criteria. This review seeks to summarize the evidence about the most relevant causes of liver involvement in CVID, including nodular regenerative hyperplasia (NRH), infections and malignancies. We also describe the clinical features of liver disease in some monogenic forms of PID included in the clinical spectrum of CVID as ICOS, NFKB1, NFKB2, CTLA-4, PI3Kδ pathway, ADA2, and IL21-R genetic defects. Finally, we discuss the clinical applications of the various diagnostic tools and the possible therapeutic approaches for the management of liver involvement in the context of CVID.

Gastrointestinal Disorders Associated with Primary Immunodeficiency Diseases

There are now 354 inborn errors of immunity (primary immunodeficiency diseases (PIDDs)) with 344 distinct molecular etiologies reported according to the International Union of Immunological Sciences (IUIS) (Clin Gastroenterol Hepatol 11: p. 1050-63, 2013, Semin Gastrointest Dis 8: p. 22-32, 1997, J Clin Immunol 38: p. 96-128, 2018). Using the IUIS document as a reference and cross-checking PubMed ( www.ncbi.nlm.nih.pubmed.gov ), we found that approximately one third of the 354 diseases of impaired immunity have a gastrointestinal component [J Clin Immunol 38: p. 96-128, 2018]. Often, the gastrointestinal symptomatology and pathology is the heralding sign of a PIDD; therefore, it is important to recognize patterns of disease which may manifest along the gastrointestinal tract as a more global derangement of immune function. As such, holistic consideration of immunity is warranted in patients with clinically significant gastrointestinal disease. Here, we discuss the manifold presentations and GI-specific complications of PIDDs which could lead patients to seek advice from a variety of clinician specialists. Often, patients with these medical problems will engage general pediatricians, surgeons, gastroenterologists, rheumatologists, and clinical immunologists among others. Following delineation of the presenting concern, accurate and often molecular diagnosis is imperative and a multi-disciplinary approach warranted for optimal management. In this review, we will summarize the current state of understanding of PIDD gastrointestinal disease involvement. We will do so by focusing upon gastrointestinal disease categories (i.e., inflammatory, diarrhea, nodular lymphoid hyperplasia, liver/biliary tract, structural disease, and oncologic disease) with an intent to aid the healthcare provider who may encounter a patient with an as-yet undiagnosed PIDD who presents initially with a gastrointestinal symptom, sign, or problem.

Vedolizumab therapy in common variable immune deficiency associated enteropathy: A case series

A number of gastrointestinal complications occur in common variable immunodeficiency (CVID). Infections are one cause, but various forms of severe non-infectious enteropathy also lead to substantial morbidity. The presence of T cell lymphocytic infiltrates in the mucosa have suggested that vedolizumab, a humanized monoclonal antibody which binds to alpha4 beta7 integrin and inhibits the migration of effector T-lymphocytes into gastrointestinal tissues, would be an effective treatment. A previous report of 3 CVID cases suggested benefit in 2 subjects. In this study 7 CVID patients with severe enteropathy were treated with vedolizumab. Four of the 7 completed vedolizumab induction therapy but 3 subjects had acute decompensation during induction and treatment was stopped. While one subject showed improvement, 6 of the 7 patients were withdrawn from therapy. While vedolizumab may be of use in some CVID subjects, it was not ultimately found helpful in most of these patients.

Gastrointestinal Manifestations and Complications of Primary Immunodeficiency Disorders

Gastrointestinal (GI) involvement can be the presenting disease manifestation in patients with primary immunodeficiency disorders (PIDs). Infections and noninfectious diarrhea are frequent manifestations; however, malignancy and inflammatory and autoimmune-related GI diseases are also described. GI symptoms and disease seen in association with PIDs can mimic other diseases but are often resistant to conventional treatments owing to alternate disease mechanisms. Despite the advances in treatments for these conditions, therapy for immunodeficiency-related GI disease is often empiric.

Aberrant X chromosome skewing and acquired clonal hematopoiesis in adult-onset common variable immunodeficiency

Advances in genomic medicine have elucidated an increasing number of genetic etiologies for patients with common variable immunodeficiency (CVID). However, there is heterogeneity in clinical and immunophenotypic presentations and a limited understanding of the underlying pathophysiology of many cases. The primary defects in CVID may extend beyond the adaptive immune system, and the combined defect in both the myeloid and lymphoid compartments suggests the mechanism may involve bone marrow output and earlier progenitors. Using the methylation profile of the human androgen receptor (AR) gene as a surrogate epigenetic marker for bone marrow clonality, we examined the hematopoietic compartments of patients with CVID. Our data show that clonal hematopoiesis is common among patients with adult-onset CVID who do not have associated noninfectious complications. Nonblood tissues did not show a skewed AR methylation status, supporting a model of an acquired clonal hematopoietic event. Attenuation of memory B cell differentiation into long-lived plasma cells (CD20^–CD27⁺CD38⁺CD138⁺) was associated with marked changes in the postdifferentiation methylation profile, demonstrating the functional consequence of clonal hematopoiesis on humoral immunity in these patients. This study sheds light on a potential etiology of a subset of patients with CVID, and the findings suggest that it is a stage of an acquired lymphocyte maturation disorder.

Clonal hematopoiesis is common among a subset of patients with common variable immunodeficiency (CVID), suggesting that CVID may be a stage of lymphoid dysplasia.

Primary Immunodeficiency and the Gut

This article presents the most common gastrointestinal, hepatic, and pancreatic manifestations of the primary immunodeficiency diseases, including the appropriate laboratory testing, endoscopic evaluation, and recommendations for further management.

Humoral immunodeficiencies: conferred risk of infections and benefits of immunoglobulin replacement therapy

Primary immunodeficiency (PID) diseases result from genetic defects of the immune system that increase a patient's susceptibility to infections. The types of infections that occur in patients with PID diseases are dictated largely by the nature of the immunodeficiency, which can be defined by dysfunction of cellular or humoral defenses. An increasing number of PID diseases, including those with both cellular and humoral defects, have antibody deficiency as a major feature, and as a result can benefit from immunoglobulin replacement therapy. In fact, the most common PID diseases worldwide are antibody deficiencies and include common variable immunodeficiency, congenital agammaglobulinemia, hyper‐IgM syndrome, specific antibody deficiency, and Good syndrome. Although immunoglobulin replacement therapy is the cornerstone of treatment for the majority of these conditions, a thorough understanding of the specific infections for which these patients are at increased risk can hasten diagnosis and guide additional therapies. Moreover, the infection trends in some patients with PID disease who have profound defects of cellular immunity, such as autosomal‐dominant hyper‐IgE syndrome (Job/Buckley syndrome) or dedicator of cytokinesis 8 (DOCK8) deficiency, suggest that select patients might benefit from immunoglobulin replacement therapy even if their immunodeficiency is not limited to antibody defects. In this review, we provide an overview of the predisposition to infections seen in PID disease that may benefit from immunoglobulin replacement therapy.

Overview in the clinical management of patients with seronegative villous atrophy

Differential diagnosis and management of enteropathies found in the context of seronegative villous atrophy (VA) are still a clinical challenge. Although seronegative coeliac disease may be the most frequent cause of serology-negative VA, other conditions must be taken into account in the differential diagnosis of seronegative VA. The rarity of these enteropathies with frequent overlapping of histological features may result in misclassification of such patients as affected by a seronegative or a refractory form of coeliac disease with consequent inappropriate treatments and long-term morbidity. The aim of this review is to summarize the current knowledge and to provide an evidence base and practical algorithmic approach for the investigation and management of seronegative VA.

A High Prevalence of Gastrointestinal Manifestations in Common Variable Immunodeficiency

OBJECTIVES

Common variable immunodeficiency (CVID) is associated with a spectrum of autoimmune complications. We studied the prevalence of gastrointestinal (GI) manifestations and infections in patients with CVID.

METHODS

Complete clinical data of 132 Finnish patients with CVID (106 probable and 26 possible CVID) followed up between 2007 and 2016 were collected to a structured database. Data on endoscopies, histology, and laboratory studies were retrieved from patient files.

RESULTS

Most common referral indications were diarrhea and/or weight loss (47%-67%). Patients with probable CVID had higher fecal calprotectin and α1-antitrypsin and lower blood vitamin B12 than patients with possible CVID. Gastroscopy and colonoscopy were done to 71 (67%) and 63 (59%) patients with probable CVID, respectively. Endoscopies showed that 15% of them had chronic active gastritis and 17% atrophic gastritis and 3% had gastric adenocarcinoma. A celiac sprue-like condition was found in 7 patients (10%), of whom 3 responded to a gluten-free diet. Colonoscopies demonstrated unspecific colitis (14%), ulcerative colitis (8%), microscopic colitis (10%), and Crohn's disease (2%). Colonic polyps were noted in 30% of patients, and 3% had lower GI malignancies. Thirty-five patients with CVID had bacterial or parasitic gastroenteritis; chronic norovirus was detected in 4 patients with probable CVID. Patients with GI inflammation had higher levels of fecal calprotectin and blood CD8 T lymphocytes but lower counts of CD19CD27 memory B cells and/or CD19 B cells. Immunophenotype with low B-cell counts was associated with higher fecal calprotectin levels.

DISCUSSION

Patients with CVID had a high prevalence of GI manifestations and infections of the GI tract. GI inflammation was associated with a distinct immunophenotype and elevated fecal calprotectin.

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.

CVID enteropathy is characterized by exceeding low mucosal IgA levels and interferon-driven inflammation possibly related to the presence of a pathobiont

Common variable immunodeficiency (CVID), the most common symptomatic primary antibody deficiency, is accompanied in some patients by a duodenal inflammation and malabsorption syndrome known as CVID enteropathy (E-CVID).The goal of this study was to investigate the immunological abnormalities in CVID patients that lead to enteropathy as well as the contribution of intestinal microbiota to this process.We found that, in contrast to noE-CVID patients (without enteropathy), E-CVID patients have exceedingly low levels of IgA in duodenal tissues. In addition, using transkingdom network analysis of the duodenal microbiome, we identified Acinetobacter baumannii as a candidate pathobiont in E-CVID. Finally, we found that E-CVID patients exhibit a pronounced activation of immune genes and down-regulation of epithelial lipid metabolism genes. We conclude that in the virtual absence of mucosal IgA, pathobionts such as A. baumannii, may induce inflammation that re-directs intestinal molecular pathways from lipid metabolism to immune processes responsible for enteropathy.

Gastrointestinal Presentations of Common Variable Immunodeficiency: Hiding in Plain Sight

Primary immunodeficiency disorders typically have an onset in childhood. The suspicion for these conditions usually arises from a history of recurrent respiratory, gastrointestinal, or cutaneous infections with a history often dating back to infancy or early childhood. However, adults can also be affected. Common variable immunodeficiency, which usually has an onset/diagnosis in adulthood, is the most common symptomatic primary immunodeficiency. However, as its presentation could be manifold, its diagnosis is often delayed. The gastrointestinal tract is the second most affected system after the respiratory tract; symptoms associated with the gastrointestinal tract are often intractable. As patients with common variable immunodeficiency are often misdiagnosed, a high index of suspicion and clinical correlation is required for the appropriate diagnosis of this potentially debilitating condition.

Apoptotic colopathy: a pragmatic approach to diagnosis

‘Apoptotic colopathy’ is an umbrella term signifying a pattern of injury where the gastrointestinal biopsy shows a colitic picture with apoptosis as the predominant histological feature. Although the entities within apoptotic colopathy share a common histological feature— ‘apoptosis’, there is a list of varied clinical differential diagnoses that produce this similar histological pattern of injury. These include graft-versus-host disease, drug-induced injury due to multiple drugs (in particular, mycophenolate mofetil, check point inhibitor therapy and some others), infections (particularly cytomegalovirus, adenovirus and some others), immune disorders and other miscellaneous causes. However, the management of these varied differentials is strikingly different, thus necessitating an algorithmic approach for accurate diagnosis and optimal patient management. A definitive diagnosis requires interpretation of varied histological findings in the appropriate clinical context including clinical history, drug history and laboratory findings. This review will focus on the histopathological findings of varied entities that can manifest as ‘apoptotic colopathy’ on assessment of colonic biopsies.

B Cell Defects Observed in Nod2 Knockout Mice Are a Consequence of a Dock2 Mutation Frequently Found in Inbred Strains

Phenotypic differences among substrains of laboratory mice due to spontaneous mutations or pre-existing genetic variation confound the interpretation of targeted mutagenesis experiments and contribute to challenges with reproducibility across institutions. Notably, C57BL/6 Hsd mice and gene-targeted mice that have been backcrossed to this substrain have been reported to harbor a duplication in exons 28 and 29 of Dock2 In this study, we demonstrate the presence of this Dock2 variant in the widely used Nod2-/- mice. Nucleotide-binding oligomerization domain-containing protein 2 (NOD2) is a cytosolic innate immune receptor associated with inflammatory bowel disease susceptibility. Consistent with a role of NOD2 in an immunological disorder, Nod2-/- mice bred at our institution displayed multiple B cell defects including deficiencies in recirculating B cells, marginal zone B cells, and B1a cells in vivo, as well as defects in class switch recombination in vitro. However, we found that these effects are due to the Dock2 variant and are independent of Nod2 deletion. Despite originating from the same gene-targeted founder mice, Nod2-/- mice from another source did not harbor the Dock2 variant or B cell defects. Finally, we show that Dock2-/- mice display the same B cell defects as mice harboring the Dock2 variant, confirming that the variant is a loss-of-function mutation and is sufficient to explain the alterations to the B cell compartment observed in Nod2-/- mice. Our findings highlight the effects of confounding mutations from widely used inbred strains on gene-targeted mice and reveal new functions of DOCK2 in B cells.

Inflammatory and infectious manifestations of immunodeficiency in the gastrointestinal tract

Immune compromise may result from genetic abnormalities, HIV/AIDS, or consequences of therapy for neoplastic and autoimmune diseases. Many immunocompromised patients develop severe gastrointestinal symptoms, particularly diarrhea, accompanied by non-specific or mild endoscopic abnormalities; mucosal biopsy with pathologic interpretation has a major role in the diagnosis and management of these patients. Immunocompromised individuals are at risk for all the diseases that affect those with a healthy immune system, but they are also prone to other illnesses that rarely affect immunocompetent patients. This review discusses the gastrointestinal manifestations of primary and acquired immunodeficiency, chemotherapy-related injury, and infections that show a predilection for immunocompromised patients. Key histologic features and relevant differential diagnoses are emphasized.