Acquired Immunodeficiency Syndrome (AIDS) represents the most advanced stage of human immunodeficiency virus (HIV) infection. HIV weakens the immune system, and AIDS manifests when this weakening becomes severe. It signifies a profound compromise of the body’s defenses, making individuals highly susceptible to various illnesses that a healthy immune system would typically manage.
The Immune System and AIDS Progression
HIV primarily targets and destroys CD4+ T cells, which are a type of white blood cell crucial for the immune system’s function. Upon entering the body, HIV binds to the CD4 molecule on these helper T cells and replicates within them, leading to their destruction.
As HIV continues to replicate and destroy CD4+ T cells, the CD4 cell count in the blood gradually declines. This reduction severely impairs the immune system’s capacity to combat infections. The body becomes vulnerable to opportunistic infections and certain cancers.
Key AIDS-Defining Conditions
A diagnosis of AIDS is often made when an individual with HIV develops specific opportunistic infections or cancers, known as AIDS-defining conditions. These conditions emerge because the severely weakened immune system can no longer control pathogens that are usually harmless.
- Pneumocystis pneumonia (PCP) is a common fungal lung infection, often presenting with fever, a dry cough, and shortness of breath.
- Kaposi’s sarcoma (KS) is a type of cancer forming growths on the skin, lymph nodes, or internal organs. These lesions typically appear as painless, discolored patches or nodules.
- AIDS-related wasting syndrome involves involuntary and significant weight loss, often accompanied by persistent fever, chronic diarrhea, or weakness. It signifies a loss of lean body mass.
- Cryptosporidiosis is a parasitic infection causing chronic, severe diarrhea, leading to dehydration and malnutrition.
- Toxoplasmosis of the brain, caused by a parasite, often manifests with neurological symptoms like headaches, confusion, seizures, or focal weakness.
- Cytomegalovirus (CMV) retinitis is a serious eye infection that can cause floaters, blurred vision, or blind spots, potentially leading to vision loss or blindness if untreated.
Common Physical Signs
Beyond the specific AIDS-defining conditions, individuals with advanced HIV often exhibit a range of more general physical signs due to the compromised immune system. These broader manifestations can indicate advanced disease progression.
Persistent fever and chronic fatigue are frequently reported, contributing to a general feeling of unwellness. Unexplained and significant weight loss, not attributed to changes in diet or exercise, is another common sign. Chronic diarrhea can also be a persistent issue, further contributing to weight loss and nutritional deficiencies.
Swollen lymph nodes, particularly in the neck, armpits, or groin, may persist for extended periods. Skin rashes and lesions, sometimes discolored or purplish, can appear on various parts of the body. Neurological symptoms, such as memory loss, difficulty concentrating, depression, or other cognitive changes, can also develop.
Confirming an AIDS Diagnosis
A formal diagnosis of AIDS relies on specific medical criteria established by health organizations. The primary criteria include a significantly low CD4 cell count and/or the presence of one or more AIDS-defining conditions.
A CD4 cell count below 200 cells per cubic millimeter of blood is a key indicator of AIDS, regardless of whether opportunistic infections are present. For comparison, a healthy immune system typically has CD4 counts between 500 and 1,500 cells/mm³. The presence of any AIDS-defining condition, even with a CD4 count above 200, also leads to an AIDS diagnosis.
While viral load tests measure the amount of HIV in the blood and are crucial for monitoring the effectiveness of antiretroviral therapy, they are not a direct diagnostic criterion for AIDS. Viral load indicates how actively the virus is replicating, but the CD4 count and the manifestation of opportunistic infections are the definitive factors for an AIDS diagnosis.