Hepatitis in common variable immunodeficiency

Autoimmune disorders associated with common variable immunodeficiency: prediction, diagnosis, and treatment

INTRODUCTION

Common variable immunodeficiency (CVID) is the most common symptomatic primary immunodeficiency. Due to the wide spectrum of the CVID manifestations, the differential diagnosis becomes complicated, ends in a diagnostic delay and increased morbidity and mortality rates. Autoimmunity is one of the important complications associated with CVID. While immunoglobulin replacement therapy has considerably decreased the mortality rate in CVID patients, mainly infection-related mortality, other complications such as autoimmunity appeared prevalent and, in some cases, life threatening.

AREAS COVERED

In this article, genetics, responsible immune defects, autoimmune manifestations in different organs, and the diagnosis and treatment processes in CVID patients are reviewed, after searching the literature about these topics.

EXPERT OPINION

Considering the many phenotypes of CVID and the fact that it remained undiagnosed until older ages, it is important to include various manifestations of CVID in the differential diagnosis. Due to the different manifestations of CVID, including autoimmune diseases, interdisciplinary collaboration of physicians from different fields is highly recommended, as discussed in the manuscript. Meanwhile, it is important to determine which patients could benefit from genetic diagnostic studies since such studies are not necessary for establishing the diagnosis of CVID.

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.

Liver disease accompanied by enteropathy in common variable immunodeficiency: Common pathophysiological mechanisms

Common variable immunodeficiency (CVID) is one of the inborn errors of immunity that have the greatest clinical impact. Rates of morbidity and mortality are higher in patients with CVID who develop liver disease than in those who do not. The main liver disorder in CVID is nodular regenerative hyperplasia (NRH), the cause of which remains unclear and for which there is as yet no treatment. The etiology of liver disease in CVID is determined by analyzing the liver injury and the associated conditions. The objective of this study was to compare CVID patients with and without liver–spleen axis abnormalities in terms of clinical characteristics, as well as to analyze liver and duodenal biopsies from those with portal hypertension (PH), to elucidate the pathophysiology of liver injury. Patients were divided into three groups: Those with liver disease/PH, those with isolated splenomegaly, and those without liver–spleen axis abnormalities. Clinical and biochemical data were collected. Among 141 CVID patients, 46 (32.6%) had liver disease/PH; 27 (19.1%) had isolated splenomegaly; and 68 (48.2%) had no liver–spleen axis abnormalities. Among the liver disease/PH group, patients, even those with mild or no biochemical changes, had clinical manifestations of PH, mainly splenomegaly, thrombocytopenia, and esophageal varices. Duodenal celiac pattern was found to correlate with PH (p < 0.001). We identified NRH in the livers of all patients with PH (n = 11). Lymphocytic infiltration into the duodenal mucosa also correlated with PH. Electron microscopy of liver biopsy specimens showed varying degrees of lymphocytic infiltration and hepatocyte degeneration, which is a probable mechanism of lymphocyte-mediated cytotoxicity against hepatocytes and enterocytes. In comparison with the CVID patients without PH, those with PH were more likely to have lymphadenopathy (p < 0.001), elevated β₂-microglobulin (p < 0.001), low B-lymphocyte counts (p < 0.05), and low natural killer-lymphocyte counts (p < 0.05). In CVID patients, liver disease/PH is common and regular imaging follow-up is necessary. These patients have a distinct immunological phenotype that may predispose to liver and duodenal injury from lymphocyte-mediated cytotoxicity. Further studies could elucidate the cause of this immune-mediated mechanism and its treatment options.

Liver Histology in Short Telomere Syndrome: A Case Report and Review of the Literature

Short telomere syndrome (STS) encompasses a broad family of genetically inherited conditions caused by various mutations in telomerase and other telomere maintenance genes, resulting in premature telomere shortening. STS involves a variety of clinical manifestations, including dyskeratosis congenita, premature achromotrichia, bone marrow failure, immunodeficiency, pulmonary fibrosis and liver disease. Liver histopathologic features in STS patients have not been well characterized. We report a 46-year-old male patient who presented for dyspnea. The patient had a complicated medical history significant for immune thrombocytopenic purpura and splenectomy, recurrent respiratory tract infections, pneumonia, primary immunodeficiency, and severe hepatopulmonary syndrome. He and his brother both developed gray hair by their late 20s. He had a long history of intermittently elevated liver enzymes starting at age 33. These clinical manifestations prompted an evaluation for a possible telomere biology disorder, which revealed the telomere length was critically short and fell at or below the first percentile for age, supporting the diagnosis. The liver biopsy showed marked portal inflammation with interface hepatitis, ductular reaction and frequent foci of lobular inflammation with focal hepatocyte dropout. Hepatocytes around the portal tracts demonstrated ballooning degeneration and occasional Mallory-Denk bodies. A trichrome stain highlighted bridging fibrosis. A literature review shows liver histology is available in only a small number of STS patients, demonstrating a variety of morphologic features. Our case and others suggest liver disease associated with STS exhibits a spectrum of histopathology. Being aware of these features is important for establishing the correct diagnosis of STS which is under recognized.

State-of-the-art diagnostic evaluation of common variable immunodeficiency

OBJECTIVE

To summarize the current understanding of diagnostic and postdiagnostic evaluation of common variable immunodeficiency (CVID).

DATA SOURCES

PubMed Central database.

STUDY SELECTIONS

Original research articles and review articles from 2015 to 2020 including seminal articles that shaped the diagnostic and postdiagnostic evaluation of CVID were incorporated. This work focuses on initial diagnosis of CVID, genetic evaluations, and postdiagnostic assessment of respiratory, gastrointestinal, and hepatobiliary diseases including spleen and lymph node enlargement.

RESULTS

CVID presents not only with frequent infections but also with noninfectious complications such as autoimmunity, gastrointestinal disease, chronic lung disease, granulomas, liver disease, lymphoid hyperplasia, splenomegaly, or malignancy. The risk of morbidity and mortality is higher in patients with CVID and noninfectious complications. Detailed diagnostic approaches, which may incorporate genetic testing, can aid characterization of individual CVID cases and shape treatment in some instances. Moreover, continued evaluation after CVID diagnosis is key to optimal management of this complex disorder. These postdiagnostic evaluations include pulmonary function testing, radiologic studies, and laboratory evaluations that may be conducted at frequencies determined by disease activity.

CONCLUSION

Although the diagnosis can be achieved similarly in all patients with CVID, those with noninfectious complications have distinct concerns during clinical evaluation. State-of-the-art workup of CVID with noninfectious complications typically includes genetic analysis, which may shape precision therapy, and thoughtful application of postdiagnostic tests that monitor the presence and progression of disease in the myriad of tissues that may be affected. Even with recent advancements, knowledge gaps in diagnosis, prognosis, and treatment of CVID persist, and continued research efforts are needed.

Spectrum of Hepatic Manifestations of Common Variable Immunodeficiency

Common variable immunodeficiency (CVID) has a heterogenous clinical presentation and can be challenging to diagnose. Distinct histologic changes have been linked with CVID in several organ systems, which can help identify the correct diagnosis. In this study we review a cohort of hepatic CVID biopsies, to better define the spectrum of histologic and biochemical alterations. We reviewed 26 liver biopsies from 24 patients with CVID, obtained at 4 institutions between 2010 and 2019. Histologic slides were examined, and pathologic, biochemical, and clinical features were recorded. A control cohort of 21 patients with nodular regenerative hyperplasia (NRH) but lacking CVID was also examined. Liver function tests were frequently abnormal, especially alkaline phosphatase (median: 193 IU/L) and aspartate transaminase (median: 56 U/L), elevated in 23 and 17 of 25 biopsies, respectively. Fifteen patients had CVID involvement of other organs. Histologic features of primary biliary cholangitis were present in 2 patients, with florid duct lesions and prominent bile duct injury, in association with positive antimitochondrial antibodies. Among the other 24 biopsies, mild to moderate portal and lobular inflammation were present in 18 and 17 of 24 biopsies, respectively. Overall, 22 of 24 biopsies showed NRH-like changes. Plasma cell were absent. A distinct pattern of pericellular fibrosis was present in 23 of 26 biopsies overall. Involvement ranged from focal centrizonal fibrosis to bridging fibrosis and was accompanied by increased intrasinusoidal lymphocytes in 13 of 24 biopsies. Pericellular fibrosis was identified in 1 of 21 biopsies in the control cohort. Additional findings included granulomatous inflammation or nonhepatocellular foreign body-type multinucleate giant cells, identified in 4 biopsies. Three of 6 examined biopsies also demonstrated focal hepatocellular copper deposition. Hepatic disease in CVID is often associated with elevated alkaline phosphatase and aspartate transaminase and is characterized histologically by the mild nonspecific portal and lobular hepatitis, absence of plasma cells, NRH-like changes, and less commonly, typical histologic features of primary biliary cholangitis. We have also identified a distinctive pattern of delicate pericellular fibrosis that is a helpful clue to the diagnosis of hepatic disease in CVID, especially when accompanied by NRH-like changes.

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 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.

Autoimmunity in common variable immunodeficiency

OBJECTIVE

Common variable immunodeficiency (CVID) is a primary immunodeficiency that is clinically heterogeneous, characterized by both infectious and noninfectious complications. Although the hallmark of disease presentation is commonly a history of recurrent sinopulmonary infections, autoimmunity and noninfectious inflammatory conditions are increasingly associated with CVID.

DATA SOURCES

A comprehensive literature search using PubMed of basic science and clinical articles was performed.

STUDY SELECTIONS

Articles discussing the association of autoimmunity with primary immunodeficiency, specifically CVID, were selected.

RESULTS

The most common autoimmune conditions are cytopenias, including immune thrombocytopenia purpura and hemolytic anemia, but organ-specific autoimmune/inflammatory complications involving the gastrointestinal, skin, joints, connective tissue, and respiratory tract. In most cases, immunoglobulin replacement therapy does not ameliorate or treat these inflammatory complications, and additional immunomodulatory treatments are needed.

CONCLUSION

Mechanisms producing these conditions are poorly understood but include cytokine and cellular inflammatory pathways, and loss of tolerance to self-antigens through the multiple signaling molecules and pathways common to tolerance and immune deficiency.

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.

Common Variable Immunodeficiency and Liver Involvement

Common variable immunodeficiency (CVID) is a primary B-cell immunodeficiency disorder, characterized by remarkable hypogammaglobulinemia. The disease can develop at any age without gender predominance. The prevalence of CVID varies widely worldwide. The underlying causes of CVID remain largely unknown; primary B-cell dysfunctions, defects in T cells and antigen-presenting cells are involved. Although some monogenetic defects have been identified in some CVID patients, it is likely that CVID is polygenic. Patients with CVID develop recurrent and chronic infections (e.g., bacterial infections of the respiratory or gastrointestinal tract), autoimmune diseases, lymphoproliferation, malignancies, and granulomatous lesions. Interestingly, autoimmunity can be the only clinical manifestation of CVID at the time of diagnosis and may even develop prior to hypogammaglobulinemia. The diagnosis of CVID is largely based on the criteria established by European Society for Immunodeficiencies and Pan-American Group for Immunodeficiency (ESID/PAGID) and with some recent modifications. The disease can affect multiple organs, including the liver. Clinical features of CVID patients with liver involvement include abnormal liver biochemistries, primarily elevation of alkaline phosphatase (ALP), nodular regenerative hyperplasia (NRH), or liver cirrhosis and its complications. Replacement therapy with immunoglobulin (Ig) and anti-infection therapy are the primary treatment regimen for CVID patients. No specific therapy for liver involvement of CVID is currently available, and liver transplantation is an option only in select cases. The prognosis of CVID varies widely. Further understanding in the etiology and pathophysiology will facilitate early diagnosis and treatments to improve prognosis.

Granulomas in the Liver, with a Focus on Infectious Causes

Hepatic granulomas are encountered in approximately 2% to 10% of liver biopsies. There are many potential infectious and noninfectious causes; granulomas can be generally classified by their morphology, which may be helpful in refining the differential diagnosis. This article provides a review of hepatic granulomas with an emphasis on infectious causes.

Indolent cytotoxic T cell lymphoproliferation associated with nodular regenerative hyperplasia: a common liver lesion in the context of common variable immunodeficiency disorder

Patients with common variable immunodeficiency disorder (CVID) are subject to lymphoproliferative disorders and predisposed to lymphoma. Some patients may also develop liver lesions. The purpose of this study was to define clinical and histopathological features of patients with CVID presenting with liver lesions suspicious of lymphoma. Four CVID cases corresponding to these criteria were retrieved from our files. Liver biopsy specimens were subjected to morphologic, immunophenotypic and molecular analysis. All patients presented with hepatosplenomegaly and two furthermore with lymphadenopathy. The clinical working diagnosis in the four cases was lymphoma. All liver biopsies revealed nodular regenerative hyperplasia (NRH), associated with mild to marked sinusoid lymphocytic infiltrate consisting of "activated" cytotoxic T cells (CD8+, Tia1+, granzyme B+, TCRβF1+, CD56-). EBER was negative in all cases. T cell clonality was found in one of the two interpretable cases. All patients had an indolent course and clinical symptoms regressed with immunoglobulin replacement. This study suggests that indolent proliferation in the liver sinusoid of cytotoxic T cell associated with NRH is a specific liver lesion in the context of CVID. In CVID patients clinically suspected of lymphoma, pathologists should avoid a misdiagnosis of aggressive T cell lymphoma with a risk of over treatment.

Common Variable Immunodeficiency: Diagnosis, Management, and Treatment

Common variable immunodeficiency (CVID) refers to a grouping of antibody deficiencies that lack a more specific genetic or phenotypic classification. It is the immunodeficiency classification with the greatest number of constituents, likely because of the numerous ways in which antibody production can be impaired and the frequency in which antibody production becomes impaired in human beings. CVID comprises a heterogeneous group of rare diseases. Consequently, CVID presents a significant challenge for researchers and clinicians. Despite these difficulties, both our understanding of and ability to manage this grouping of complex immune diseases has advanced significantly over the past 60 years.

Diagnosis and treatment of gastrointestinal disorders in patients with primary immunodeficiency

Gastrointestinal disorders such as chronic or acute diarrhea, malabsorption, abdominal pain, and inflammatory bowel diseases can indicate immune deficiency. The gastrointestinal tract is the largest lymphoid organ in the body, so it is not surprising that intestinal diseases are common among immunodeficient patients. Gastroenterologists therefore must be able to diagnose and treat patients with primary immunodeficiency. Immune-related gastrointestinal diseases can be classified as those that develop primarily via autoimmunity, infection, an inflammatory response, or malignancy. Immunodeficient and immunocompetent patients with gastrointestinal diseases present with similar symptoms. However, intestinal biopsy specimens from immunodeficient patients often have distinct histologic features, and these patients often fail to respond to conventional therapies. Therefore, early recognition of symptoms and referral to an immunologist for a basic immune evaluation is required to select appropriate treatments. Therapies for primary immunodeficiency comprise immunoglobulin replacement, antibiotics, and, in severe cases, bone marrow transplantation. Treatment of immunodeficient patients with concomitant gastrointestinal disease can be challenging, and therapy with immunomodulators often is required for severe disease. This review aims to guide gastroenterologists in the diagnosis and treatment of patients with primary immunodeficiency.

Aspergillosis after liver transplantation in the context of common variable immunodeficiency: case report

Common variable immunodeficiency (CVID) is the most common primary immune defect, resulting in hypogammaglobulinemia as well as deficits in cell-mediated immunity. Although it mainly manifests in immunodeficiency and related infection, CVID can also be associated with autoimmune phenomena such as immune thrombocytopenic purpura, hemolytic anemia, rheumatoid arthritis, lupus, primary biliary cirrhosis, and autoimmune hepatitis (AIH). AIH is a less common but serious complication of CVID, which can result in early cirrhosis, ascites, and even hepatocellular carcinoma. Here, we discuss a recent case of transplantation for cirrhosis secondary to AIH in the context of CVID. Although the patient's surgery occurred without complication, he rapidly developed fulminant alveolar hemorrhage and seizures, and died secondary to disseminated neuroaspergillosis.

Liver transplantation for severe hepatitis in patients with common variable immunodeficiency

CVID is a heterogeneous group of primary immunodeficiency diseases characterized by hypogammaglobulinemia, recurrent bacterial infections, and frequent autoimmune manifestations. The post-transplant course of liver transplant recipients with CVID is rarely described. We report two patients with CVID complicated by severe enteropathy who underwent living donor liver transplantation for liver failure because of severe hepatitis. The post-transplant course was complicated by recurrent acute rejection, leading to ductopenic rejection in one and recurrent hepatitis in the other. We reviewed the tissue samples histologically and immunohistochemically. Native livers showed submassive hepatocyte necrosis in one and cirrhotic liver with active hepatitis in the other, both with infiltration of CD8+ T cells accompanied by endothelialitis and bile duct damage; the intestine contained increased numbers of intraepithelial CD8+ T cells with apoptosis of epithelial cells. The liver allograft exhibited acute rejection, with prominent CD8+ T cells infiltrating the bile duct or endothelium. In the allograft following the diagnosis of post-transplant recurrent hepatitis, CD8+ T cells comprised the majority of infiltrating cells in portal areas spilling over into hepatic parenchyma. Our cases suggest that T cells contribute to the pathogenesis of CVID in native organs as well as allografts and may constitute evidence of T-cell deregulation in the pathogenesis of CVID.

Recognizing gastrointestinal and hepatic manifestations of primary immunodeficiency diseases

Given the complex immune function of the gastrointestinal (GI) tract, it is not surprising that many children with primary immunodeficiencies present with GI tract manifestations. Although many immunodeficiency disorders present with overt evidence of immune dysregulation, a few can present in older children with more subtle signs and symptoms. Such children may present first to a gastroenterologist with common symptoms, including malabsorption, diarrhea, hepatomegaly, or inflammatory bowel disease, which may actually be a manifestation of their underlying immune disorder. A thorough clinical history in combination with a careful review of histology from biopsies may reveal clues that one is dealing with a disease entity outside the norm and may prompt additional laboratory studies beyond the usual set of screening laboratory tests. Once the true underlying diagnosis is revealed, more appropriate therapy can be initiated. Additionally, more appropriate anticipatory guidance regarding the expected disease course, response to medications, and any additional risks that therapy may entail can be provided to the family.

Advances in hepatobiliary pathology: update for 2010

Recent publications on hepatology and hepatic pathology provide a wealth of new information on wideranging topics. Morphologic aspects of liver disease associated with hepatitis B and C viruses, autoimmune hepatitis, and HIV infection were addressed, as was the prevalent problem of nonalcoholic fatty liver disease. Advances in diagnosis and pathogenesis of primary biliary cirrhosis, primary sclerosing cholangitis, and the increasingly complex spectrum of IgG4 hepatobiliary diseases were also reported. The histologic and immunohistochemical features of the rare "calcifying nested stromal-epithelial tumor" of the liver were described in a 9-case series. For benign and malignant liver tumors, immunohistochemistry plays a major diagnostic role, and several recent studies demonstrate the value of immunostains in distinguishing between liver-cell adenoma and focal nodular hyperplasia.

More than just infections: an update on primary immune deficiencies

PURPOSE OF REVIEW

The general pediatrician should be empowered to utilize continuity of care for the recognition of unusual or severe patterns of infection. With the burgeoning field of genetics, primary immune deficiencies (PIDs) can be diagnosed and treated earlier to provide better outcomes for patients and families. Improved treatment modalities have redefined expectations for many infants born with PIDs.

RECENT FINDINGS

The prevalence of PIDs increases as researchers discover novel immunodeficiency syndromes and as clinicians increasingly recognize and diagnose nuanced presentations of immunodeficiency. Novel immunodeficiency syndromes associated with mutations in DOCK8, CARD9, and PRKDC recently have been described. For the first time in the United States, newborns from an entire state were screened for lymphopenia, allowing potentially life-saving early diagnosis of the most severe forms of PID before the onset of symptoms. Hematopoietic stem cell transplantation (HSCT) and gene therapy continue to be evaluated as curative treatments with increasing success rates for some of the most severe PIDs.

SUMMARY

The field of PID continues to expand and advancements have been made in earlier diagnosis and screening. Comparative effectiveness research into treatment modalities offered to patients with PID is leading to a better understanding of optimal therapies for specific PIDs. In the meantime, the advocacy efforts of established and emerging PID networks promote excellence in clinical recognition and treatment of PIDs in children.

Autoimmunity in common variable immunodeficiency

Common variable immunodeficiency (CVID) is the most common clinically significant primary immune defect. Although the hallmark of CVID is hypogammaglobulinemia, the intrinsic dysregulation of the immune system leads to defective T-cell activation and proliferation, as well as dendritic cell and cytokine defects. Although 70% to 80% of patients have had recurrent sinopulmonary infections, autoimmunity and inflammatory complications are also common. The most common autoimmune conditions are immune thrombocytopenic purpura and hemolytic anemia, but other autoimmune complications arise, including rheumatoid arthritis, pernicious anemia, primary biliary cirrhosis, thyroiditis, sicca syndrome, systemic lupus, and inflammatory bowel disease. Treatment of autoimmunity includes high-dose immunoglobulins, corticosteroids, selected immunosuppressants, and other immune modulators. This review focuses on autoimmune conditions associated with CVID, potential mechanisms of immune dysregulation, and therapeutic strategies.

Pathogenesis and treatment of gastrointestinal disease in antibody deficiency syndromes

Primary humoral immune deficiencies are characterized by limited antibody responses secondary to either impaired B-lymphocyte development or B-cell responses to T-lymphocyte signals. Given that the gastrointestinal tract is the largest lymphoid organ in the body, it is not surprising that intestinal diseases are common in immunodeficiency. These gastrointestinal diseases can be classified into one of 4 groups, infection, malignancy, inflammatory, and autoimmune, and can mimic other known disease processes, such as inflammatory bowel disease and celiac sprue. The exact pathogenesis of these gastrointestinal disorders in the setting of systemic immunodeficiency is still under investigation. However, studies suggest that defects in antibody deficiency alone do not result in gastrointestinal disease but rather that defects in cellular immunity are also involved. Treatment is difficult given an already immunocompromised state, and often therapy with immunomodulators is required for more severe processes.