Acquired immunodeficiency syndrome
Acquired immunodeficiency syndrome: Excerpt from Professional Guide to Diseases (Eighth Edition)
Acquired immunodeficiency syndrome (AIDS) is a serious secondary immunodeficiency disorder caused by the human immunodeficiency virus (HIV). Both diseases are characterized by the progressive destruction of cell-mediated (T-cell) immunity with subsequent effects on humoral (B-cell) immunity because of the pivotal role of the CD4+ helper T cells in immune reactions. The resultant immunodeficiency makes the patient susceptible to opportunistic infections, unusual cancers, and other abnormalities. (See Common infections and neoplasms in HIV and AIDS.)
The Centers for Disease Control and Prevention (CDC) first described AIDS in 1981. Since then, the CDC has declared a case surveillance definition for AIDS and modified it several times, most recently in January 2000.
Causes and incidence
AIDS results from infection with HIV, which has two forms: HIV-1 and HIV-2. Both forms of HIV have the same modes of transmission and similar opportunistic infections associated with AIDS, but studies indicate that HIV-2 develops more slowly and presents with milder symptoms than HIV-1.
Transmission occurs through contact with infected blood or body fluids and is associated with identifiable high-risk behaviors. It’s disproportionately represented in:
❑ homosexual and bisexual men
❑ persons who use illicit I.V. drugs
❑ neonates of infected females
❑ recipients of contaminated blood or blood products (incidence dramatically decreased since mid-1985)
❑ heterosexual partners of persons in the former groups.
Signs and symptoms
A person with HIV may remain asymptomatic for months or years. Initially, laboratory evidence or seroconversion to HIV antibodies may be the only clinical evidence of infection. However, as the disease progresses, the patient may develop generalized adenopathy and nonspecific signs and symptoms, such as weight loss, fatigue, night sweats, and fevers. As the patient’s T-cell count lowers further, neurologic symptoms, opportunistic infections, and certain normally rare cancers may develop. HIV also destroys lymph nodes and immunologic organs, leading to major dysfunctions of the immunological system. Eventually, HIV advances to AIDS. (Some individuals, termed nonprogressors, develop AIDS very slowly or not at all. They seem to have genetic differences that prevent the virus from attaching to certain immune receptors.)
PEDIATRIC TIP The clinical course varies slightly in children, who have a shorter incubation time (mean, 17 months.) Signs and symptoms resemble those in adults, except for findings related to sexually transmitted disease (STD). Children show virtually all of the opportunistic infections observed in adults, with a higher incidence of bacterial infections: otitis media, pneumonias other than that caused by Pneumocystis carinii, sepsis, chronic salivary gland enlargement, and lymphoid interstitial pneumonia.
Diagnosis
CONFIRMING DIAGNOSIS Signs and symptoms may occur at any time after infection with HIV, but AIDS isn’t officially diagnosed until the patient’s CD4+ T-cell count falls below 200 cells/µl.
The most commonly performed tests, antibody tests, indicate HIV infection indirectly by revealing HIV antibodies. The recommended protocol requires initial screening of individuals and blood products with an enzyme-linked immunosorbent assay (ELISA). A positive ELISA should be repeated and then confirmed by an alternate method, usually the Western blot or an immunofluorescence assay. The radioimmunoprecipitation assay is considered more sensitive and specific than the Western blot, but because it requires radioactive materials, it’s a poor choice for routine screening. In addition, antibody testing isn’t reliable. Because people produce detectable levels of antibodies at different rates — a “window” varying from a few weeks to as long as 35 months in one documented case — an HIV-infected person can test negative for HIV antibodies. Antibody tests are also unreliable in neonates because transferred maternal antibodies persist for 6 to 10 months. To overcome these problems, direct tests are used, including antigen tests (p24 antigen), HIV cultures, nucleic acid probes of peripheral blood lymphocytes, and the polymerase chain reaction. (See Laboratory tests for diagnosing and tracking HIV and assessing immune status, page 396.)
Additional tests to support the diagnosis and help evaluate the severity of immunosuppression include CD4+ and CD8+ T-lymphocyte subset counts, erythrocyte sedimentation rate, complete blood cell count, serum beta2-microglobulin, p24 antigen, neopterin levels, and anergy testing. Because many opportunistic infections in AIDS patients are reactivations of previous infections, patients are also tested for associated neoplasms, infections, and STDs.
Treatment
There is no cure for either HIV or AIDS. However, significant advances have been made to help patients control signs and symptoms and impair disease progression. Because HIV can become resistant to any drug, health care professionals use combination treatments and multiple drug regimens to suppress the virus. Patients on medication remain infectious.
An effective method of treatment is highly active antiretroviral therapy (HAART). HAART aims to reduce the number of HIV particles in the blood as measured by viral load, thus increasing T-cell counts and improving the immunologic system’s functioning. A regular and vigilant medication regimen is critical or resistance will develop because HIV strains mutate and can become resistant to HAART relatively easily.
The nucleoside analogues (sometimes called reverse transcriptase inhibitors) have been the mainstay of AIDS therapy in recent years. These drugs interfere with viral reverse transcriptase, which impairs HIV’s ability to turn its ribonucleic acid into deoxyribonucleic acid for insertion into the host cell.
Antiretroviral therapy typically begins when the patient’s CD4+ T-cell count drops to less than 500/µl or when the patient develops an opportunistic infection. Most clinicians recommend starting the patient on a combination of these drugs in an attempt to gain the maximum benefit and to inhibit the production of resistant mutant strains of HIV. The drug combinations and dosages are then altered, depending on the patient’s response.
Increasingly, physicians are basing changes in therapy on the patient’s viral load rather than on his CD4+ T-cell count. Because the CD4+ count is influenced by the total white blood cell count, changes in the CD4+ count may have nothing to do with changes in the patient’s HIV status. Many physicians suggest that patients on antiretroviral therapy have their viral load checked every 3 months.
The increasing use of protease inhibitors (PIs) has greatly increased the life expectancy of patients with AIDS. These drugs block the enzyme protease, which HIV needs to produce virions, the viral particles that spread the virus to other cells. The use of PIs dramatically reduces viral load — sometimes to undetectable levels — while producing a corresponding increase in the CD4+ T-cell count and, because they act at a different site than nucleoside analogues, the PIs don’t produce additional adverse effects when added to a patient’s regimen.
Antiviral therapy includes the use of multiple combined drug therapies that suppress the replication of the HIV virus in the body. After antiviral therapy is initiated, treatment should be aggressive. Initially, highly active antiviral therapy, consisting of a triple drug therapy regimen — a PI and two non-nucleoside reverse transcriptase inhibitors — is recommended. In addition to these primary treatments, anti-infectives are used to combat opportunistic infections (some are used prophylactically to help patients resist opportunistic infections), and antineoplastic drugs are used to fight associated neoplasms. Supportive treatments help maintain nutritional status and relieve pain and other distressing physical and psychological symptoms.
Special considerations
❑ Advise health care workers and the public to use precautions in all situations that risk exposure to blood, body fluids, and secretions. Diligently practicing standard precautions can prevent the inadvertent transmission of AIDS and other infectious diseases that are transmitted by similar routes.
❑ Recognize that a diagnosis of AIDS is profoundly distressing because of the disease’s social impact and discouraging prognosis. The patient may lose his job and financial security as well as the support of family and friends. Do your best to help him cope with an altered body image, the emotional burden of serious illness, and the threat of death, and encourage and assist the patient in learning about AIDS societies and support programs.
Pictures
Book Source Details
- Book Title: Professional Guide to Diseases (Eighth Edition)
- Author(s): Springhouse
- Year of Publication: 2005
- Copyright Details: Professional Guide to Diseases (Eighth Edition), Copyright © 2005 Lippincott Williams & Wilkins.
More About Immune deficiency conditions
More Medical Textbooks Online about Immune deficiency conditions
Review other book chapters online related to Immune deficiency conditions:
Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
» Next page: Severe combined immunodeficiency disease (Handbook of Diseases)
Rate This Website
What do you think about the features of this website?
Take our user survey and have your say:
Website User Survey
Medical Tools & Articles:
Next articles:
Tools & Services:
Medical Articles:
Forums & Message Boards
- Ask or answer a question at the Boards:
