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  • Recurrent infections and diarrhea are the most common gastrointestinal manifestations of immunodeficiency.
  • Some pathogens (eg, Mycobacterium avium complex), are unique to immunocompromised hosts; others (eg, Cryptosporidium, Giardia lamblia) cause self-limited diarrhea in healthy hosts but chronic diarrhea in immunosuppressed patients.
  • In patients without a specific diagnosis after routine study, endoscopic evaluation with biopsy is important in establishing the diagnosis.
  • Candida species, herpes simplex virus, cytomegalovirus, and Mycobacterium species are the most frequent causative agents of infectious esophagitis in an immunocompromised host.
  • In immunocompromised patients, opportunistic infections are a major cause of abdominal pain and can evolve rapidly.
  • The frequency of intestinal lymphomas is increased in patients with common variable immunodeficiency.

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The gastrointestinal (GI) tract is the largest lymphoid organ and dysfunction of the GI tract is one of the most common manifestations of immunodeficiency. Some studies have suggested that 50–90% of patients with secondary (acquired) immunodeficiency syndromes, such as full-blown AIDS, develop significant GI symptoms. The most common GI manifestations of immunodeficiency are infection and malignancy, which correlate with the progressive deterioration of host defense systems. Patients often develop diarrhea, abdominal pain, dysphagia, and odynophagia, as well as nausea, vomiting, weight loss, and GI bleeding. The overall goal of evaluation is, therefore, to identify treatable causes of the symptoms and to preserve the function of the GI tract.

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The impaired host immune system results from either primary inherited defects or secondary acquired deficiencies resulting from infectious agents (eg, HIV) or pathologic insults, including nutritional deficiencies or the iatrogenic effects of medical interventions (eg, immunosuppressive therapies). In addition, the chronic disease burden associated with advanced age and, to a lesser degree, the poorly understood physiologic decline of host defense systems associated with aging play an important role in the development of GI symptoms in geriatric populations. A detailed description of the nature and mechanisms of the GI manifestations of each individual primary and acquired (secondary) immunodeficiency is beyond the scope of this chapter. However, a comprehensive understanding of the composition and development of the immune defense systems of the GI tract and their alterations in pathologic conditions is essential for the clinical management of GI problems associated with immunodeficiency patients.

Castle SC, Uyemura K, Fulop T, et al. Host resistance and immune responses in advanced age. Clin Geriatr Med. 2007;23:463–479.   [PubMed: 17631228]

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Pathophysiology of Gastrointestinal Defense Systems

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The intestinal epithelium serves as the major frontier of self-protection from exogenous injurious events. To defend against the vast quantity of infectious agents and toxins and ensure homeostasis of the gut epithelium for nutritional absorption, the body relies on the proper development and maintenance of the immunologic defense systems associated with the intestinal epithelium, which employs both innate and adaptive immune systems. Abnormalities occurring during normal development of the GI defense systems or inability to maintain the function of these systems, stemming from congenital abnormalities, nutritional defects, or insults from toxins (eg, ...

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