AIDS: Encyclopedia II - AIDS - Symptoms and Complications

AIDS - Symptoms and Complications

The symptoms of AIDS are primarily the result of conditions that do not normally develop in individuals with healthy immune systems. Most of these conditions are infections caused by bacteria, viruses, fungi and parasites that are normally controlled by the elements of the immune system that HIV damages. Opportunistic infections are common in people with AIDS ^[18]. Nearly every organ system is affected. People with AIDS also have an increased risk of developing various cancers such as Kaposi sarcoma, cervical cancer and cancers of the immune system known as lymphomas.

Additionally, people with AIDS often have systemic symptoms of infection like fevers, sweats (particularly at night), swollen glands, chills, weakness, and weight loss ^[19][20]. After the diagnosis of AIDS is made, the current average survival time with antiretroviral therapy is estimated to be between 4 to 5 years ^[21], but because new treatments continue to be developed and because HIV continues to evolve resistance to treatments, estimates of survival time are likely to continue to change. Without antiretroviral therapy, progression to death normally occurs within a year ^[22]. Most patients die from opportunistic infections or malignancies associated with the progressive failure of the immune system ^[23].

The rate of clinical disease progression varies widely between individuals and has been shown to be affected by many factors such as host susceptibility ^[24][25][26], health care and co-infections ^[27][28], and peculiarities of the viral strain ^[29][30][31]. Also, the specific opportunistic infections that AIDS patients develop depends in part on the prevalence of these infections in the geographic area in which the patient lives.

AIDS - The major pulmonary illnesses

• Pneumocystis jiroveci pneumonia: Pneumocystis jiroveci pneumonia (originally known as Pneumocystis carinii pneumonia, often abbreviated PCP) is relatively rare in normal, immunocompetent people but common among HIV-infected individuals. Before the advent of effective treatment and diagnosis in Western countries it was a common immediate cause of death. In developing countries, it is still one of the first indications of AIDS in untested individuals, although it does not generally occur unless the CD4 count is less than 200 per µl. ^[32]

• Tuberculosis: Among infections associated with HIV, tuberculosis (TB) is unique in that it may be transmitted to immunocompetent persons via the respiratory route, is easily treatable once identified, may occur in early-stage HIV disease, and is preventable with drug therapy. However, multi-drug resistance is a potentially serious problem. Even though its incidence has declined because of the use of directly observed therapy and other improved practices in Western countries, this is not the case in developing countries where HIV is most prevalent. In early-stage HIV infection (CD4 count >300 cells per µl), TB typically presents as a pulmonary disease. In advanced HIV infection, TB may present atypically and extrapulmonary TB is common infecting bone marrow, bone, urinary and gastrointestinal tracts, liver, regional lymph nodes, and the central nervous system.^[33]

AIDS - The major gastro-intestinal illnesses

• Esophagitis: Esophagitis is an inflammation of the lining of the lower end of the esophagus (gullet or swallowing tube leading to the stomach). In HIV infected individuals, this could be due to fungus (candidiasis), virus (herpes simplex-1 or cytomegalovirus). In rare cases, it could be due to mycobacteria ^[34].

• Unexplained chronic diarrhea: In HIV infection, there are many possible causes of diarrhea, including common bacterial (Salmonella, Shigella, Listeria, Campylobacter, or Escherichia coli) and parasitic infections, and uncommon opportunistic infections such as cryptosporidiosis, microsporidiosis, Mycobacterium avium complex (MAC) and cytomegalovirus (CMV) colitis. Diarrhea may follow a course of antibiotics (common for Clostridium difficile). It may also be a side effect of several drugs used to treat HIV, or it may simply accompany HIV infection, particularly during primary HIV infection. In the later stages of HIV infection, diarrhea is thought to be a reflection of changes in the way the intestinal tract absorbs nutrients, and may be an important component of HIV-related wasting.^[35]

AIDS - The major neurological illnesses

• Toxoplasmosis: Toxoplasmosis is a disease caused by the single-celled parasite called Toxoplasma gondii. T. gondii usually infects the brain causing toxoplasma encephalitis. It can also infect and cause disease in the eyes and lungs.^[36]

• Progressive multifocal leukoencephalopathy: Progressive multifocal leukoencephalopathy (PML) is a demyelinating disease, in which the myelin sheath covering the axons of nerve cells is gradually destroyed, impairing the transmission of nerve impulses. It is caused by a virus called JC virus which occurs in 70% of the population in latent form, causing disease only when the immune system has been severly weakened, as is the case for AIDS patients. It progresses rapidly, usually causing death within months of diagnosis.^[37]

• HIV-associated dementia: HIV-1 associated dementia (HAD) is a metabolic encephalopathy induced by HIV infection and fueled by immune activation of brain macrophages and microglia.^[38] These cells are actively infected with HIV and secrete neurotoxins of both host and viral origin. Specific neurologic impairments are manifested by cognitive, behavioral, and motor abnormalities that occur after years of HIV infection and is associated with low CD4+ T cell levels and high plasma viral loads. Prevalence is between 10-20% in Western countries^[39] and has only been seen in 1-2% of India based infections.^[40][41]

• Cryptococcal meningitis This infection of the meninges (the membrane covering the brain and spinalcord) by the fungus Cryptococcus neoformans can cause fevers, headache, fatigue, nausea, and vomiting. Patients may also develop seizures and confusion. If untreated, it can be lethal.

AIDS - The major HIV-associated malignancies

Patients with HIV infection are susceptible to a number of malignancies.^[42][43] The most common is Kaposi's sarcoma, and the appearance of this tumor in young gay men in 1981 was one of the first signals of the AIDS epidemic. In addition, patients with HIV infection have a higher incidence of certain high grade B cell lymphomas, especially Burkitt-like and large cell lymphomas. These tumors, as well as aggressive cervical cancer in women, confer a diagnosis of AIDS in patients with HIV infection. HIV-infected patients are also at increased risk of certain other tumors, such as Hodgkin's disease and anal and rectal carcinomas. However, the incidence of many common tumors, such as breast cancer or colon cancer, are not increased in HIV-infected patients. Most AIDS-associated malignancies are caused by co-infection of patients with an oncogenic DNA virus, especially Epstein-Barr virus (EBV), Kaposi's sarcoma-associated herpesvirus (KSHV), and human papillomavirus (HPV). In areas where HAART is extensively used to treat AIDS, the incidence of many AIDS-related malignancies has decreased, but at the same time malignancies overall have become the most common cause of death of HIV-infected patients.^[44]

AIDS - Other opportunistic infections

Patients with AIDS and severe immunosuppression often develop opportunistic infections that present with non-specific symptoms, especially low grade fevers and weight loss. These include infection with Mycobacterium avium-intracellulare and cytomegalovirus (CMV). CMV can also cause colitis, as described above, and CMV retinitis can cause blindness.

Adapted from the Wikipedia article "Symptoms and Complications", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki