In order to be diagnosed with AIDS, HIV-positive individuals must present with a compromised immune system. This entails a low CD4 T cell count (less than 200 cells per cubic millimeter of blood or comprising less than 14 percent of the total lymphocytes) and the presence of specific infections that normally do not appear, or are very rare, in healthy individuals.
Fungal Infections
Some disease causing agents are usually handled by the human immune system without the person knowing they were exposed, but in individuals with a compromised immune system, such as HIV-infected patients, the pathogens cause symptoms and disease. In AIDS patients, fungal infection commonly leads to yeast infections, particularly candiadiasis (the causative agent in thrush), cryptococcosis, and penicilliosis. Pneumonia caused by Pneumocystis carnii, sometimes referred to as PCP (Pneumocystis carnii pneumonia), is particularly associated with AIDS and a major cause of death in HIV-infected patients.
Cancer
Certain vascular cancers are associated with AIDS. Kaposi’s sarcoma is one such tumor of the connective tissue, appearing as dark colored bumps on the skin and thought to be due to viral co-infection with human herpesvirus-8. Some forms of lymphoma, a cancer of the white blood cells, are also associated with HIV infection. Such forms of cancer include diffuse large B-cell non-Hodgkin’s lymphoma and Burkitt’s lymphoma.
Viral and Bacterial Co-infection
Cytomegalovirus is a common infectious agent that normally causes no symptoms or disease, with up to 85 percent of the adult population having had it at some point by the age of 40 as noted by KidsHealth. But in HIV-infected individuals, CMV disease can occur. Severe herpes simplex infection is also sometimes seen in AIDS patients, as well as treatment resistant tuberculosis. Mycobacteria infections and salmonella septicemia, an often fatal blood infection due to dissemination of the bacteria into the blood, are also possible in the presence of a compromised immune system.
Protozoal Disease
A number of protozoa, miscroscopic life forms, infect immunocompromised individuals. Histoplasmosis is the most common, but cryptosporidiosis (infection with Cryptosporidium enteritis that causes intestinal distress), toxoplasmosis infection of the brain, and microsporidiosis are also seen in AIDS patients.
Systemic Physiological Breakdown
AIDS wasting syndrome is a common physiological sign of the last stage of HIV infection. The syndrome is defined by an involuntary 10 percent loss of body weight plus chronic diarrhea or fever for 30 days or more in the absence of another disease. Nervous system disorders are also common in late stages of AIDS, including progressive multifocal leukoencephalopathy, and encephalopathy.
Hairy leukoplakia is an odd sign of HIV infection. It consists of white growth on the tongue indicative of a malfunctioning immune system in the absence of an oral infection. The appearance gives it the name “hairy”.
Opportunistic
The actual cause of death in AIDS patients is due to the infections that take advantage of the compromised immune system following years of HIV infection. As the virus destroys T cells, the body cannot protect itself, giving infectious agents opportunity to destroy. From common infectious agents to rare physiological breakdown caused by the absence of protective white blood cells, AIDS-defining conditions indicate the final stage of HIV infection.
Individuals infected with HIV can find information about preventing and treating opportunistic infections at Avert’s website.
Alicia Mae Prater - Alicia received her doctorate in Experimental Pathology in 2007. She has been a freelance writer and scientific editor since 2008.
Join the Conversation