AIDS-Defining Illnesses

In addition to supporting a laboratory-based diagnosis of AIDS, the presence of an AIDS-defining
illness can be the basis for an independent, presumptive diagnosis of AIDS in a person whose HIV seropositivity and CD4-cell count are unknown.

Patients who have a weakened immune system are more prone to experiencing a variety of infections and diseases, referred to as AIDS-defining illnesses. When an AIDS-defining illness occurs, it is a sign that a patient has entered the “late stage” of HIV infection and is developing AIDS. Many individuals discover they are HIV positive at this particular stage.

AIDS-defining illnesses fall under the following four categories:

• Opportunistic infections
• Diseases affecting the central and peripheral nervous system
• Malignancies
• Wasting syndrome

1) Opportunistic infections

Opportunistic infections are caused by bacteria, viruses, and other protozoa that a healthy body normally would be capable of fighting. Opportunistic infections frequently associated with HIV and AIDS include Pneumocystis carinii pneumonia (PCP), cerebral toxoplasmosis, cytomegalovirus (CMV) infection, and disseminated Mycobacterium avium complex (MAC) infection. Antibiotic prophylaxis may prevent the onset of certain illnesses.

1. Lung
   - PCP
   - Mycobacterium tuberculosis
2. Mouth
   - Oral/esophageal candidiasis
   - Oral hairy leukoplakia (OHL)
   - Kaposi’s sarcoma (KS)
3. Liver
   - MAC
   - CMV hepatitis
4. Cerebral
   - Toxoplasmosis
   - Progressive multifocal leukoencephalopathy (PML)
5. Colon
   - CMV colitis
6. Genitals
   - Herpes simplex virus (HSV) ulcers
   - Vaginal candidiasis
   - Genital warts (Human papillomavirus - HPV)
7. Eyes
   - CMV retinitis/uveitis

2) Diseases affecting the central and peripheral nervous system

Most patients will experience neurological problems during the course of the disease. AIDS dementia complex is an AIDS-defining illness characterized by cognitive and memory impairment, as well as an impaired ability to concentrate and perform complex tasks. This illness also may affect a patient’s motor ability and his or her behavior. Other conditions include peripheral neuropathy, myopathy, and myelopathy.

3) Malignancies

Kaposi’s sarcoma (KS) is a cancer associated with HIV and AIDS. Its etiology is unknown; however, genetic, environmental, and infectious agents (eg, human herpes virus-8) play a likely role in the development of KS. Kaposi’s sarcoma often appears as lesions on the skin and may also affect the lymph glands, the gastrointestinal tract, and the lungs. Other malignancies include lymphoma, non-Hodgkin’s lymphoma, and cervical malignancies.

4) Wasting syndrome

Inadequate nutrition, untreated infections, and metabolic disturbances are believed to contribute to the wasting syndrome of AIDS.