Gastrointestinal Manifestations of Acquired Immunodeficiency Syndrome

Radiologic-Pathologic Correlation

Abstract Introduction

Opportunistic Infections AIDS-Associated Neoplasms Conclusion

Source Information References

Introduction

It is currently estimated that more than 14 million people have been infected with the human immunodeficiency virus (HIV) type 1 worldwide and that this number may exceed 40 million by the year 2000 (1). HIV is the third human retrovirus that has been identified, but it differs strikingly from the first two (human T-cell lymphotropic virus types I and II) in that it consistently leads to destruction of the cellular immune system. This destruction causes susceptibility to opportunistic infections and neoplasms and eventually results in death. The cellular receptor for HIV is the CD4 molecule on the surface of T-helper lymphocytes and, at lower density, on macrophages and microglial cells. After cellular invasion via this receptor, HIV genetic information is incorporated into the cell's chromosomal DNA. Although most patients are asymptomatic for years, viral replication remains active throughout the course of infection (2). Destruction of CD4 cells is central to immune impairment in these patients, and quantitation of these cells provides a clinically useful marker of the level of this compromise.

When HIV-infected patients become immunocompromised to the extent that normally nonpathogenic organisms produce clinical infections, they are said to have the acquired immunodeficiency syndrome (AIDS). Recently, the U.S. Centers for Disease Control and Prevention modified their definition of AIDS to include patients with CD4 cell counts below 200 cells per microliter (normal range, 800 1,200 cells per microliter), independent of the occurrence of an AIDS-defining illness (3).

A major defense mechanism of the gastrointestinal system occurs in the lymphoid tissue that underlies its mucosa. With HIV disease progression, the function of this lymphoid tissue becomes dysregulated and impaired, and the gastrointestinal tract becomes a common site of pathologic involvement of both opportunistic infections and AIDS-related neoplasms. Each anatomic segment of the gastrointestinal tract is susceptible, but the relative frequency of specific infections and neoplasms differs, as do the resulting signs and symptoms. Involvement of the luminal organs may produce odynophagia, dysphagia, malabsorption, diarrhea, wasting, and malnutrition. Involvement of the solid organs may produce pain, fever, hepatosplenomegaly, hyperamylasemia, and jaundice. Clinically, as radiologically, the signs and symptoms are often atypical because the host immune response may be greatly modified by the HIV infection.

AIDS-related illnesses within the gastrointestinal system are categorized according to the two main causes, infections (especially opportunistic) and AIDS-associated neoplasms. Immune dysfunction, as reflected by the CD4 cell count, is a major risk factor in these diseases (Table 1). In this article, the diseases found commonly within these categories are discussed and illustrated, with special attention given to the gastrointestinal manifestations.

Abstract Introduction

Opportunistic Infections AIDS-Associated Neoplasms Conclusion

Source Information References