Acquired Immunodeficiency Syndrome (AIDS) represents the most advanced stage of infection with the Human Immunodeficiency Virus (HIV). At this point, the immune system experiences severe damage, leaving the body highly vulnerable. The term “end stage” signifies a critical weakening of the body’s defenses, where it can no longer effectively combat certain diseases. This profound immunosuppression leads to the emergence of specific complications that define this advanced stage.
Understanding the End Stage of AIDS
The end stage of AIDS is primarily defined by a low count of CD4 cells, which are crucial immune cells. This count typically falls below 200 cells per cubic millimeter of blood (cells/mm³), indicating severe immune system compromise. Alternatively, the presence of specific illnesses, regardless of the CD4 count, can also signify progression to AIDS. This severe immune weakening makes the body highly susceptible to infections and cancers that a healthy immune system would normally control.
Defining Opportunistic Infections
Opportunistic infections (OIs) are a primary category of end-stage complications in AIDS. These infections are caused by various germs, including viruses, bacteria, fungi, and parasites, which typically do not cause illness in people with healthy immune systems. Their emergence signals the progression to AIDS.
One common fungal infection is Pneumocystis pneumonia (PCP), which targets the lungs and can lead to severe respiratory illness. Although less frequent due to modern treatments, PCP remains a concern for individuals with untreated HIV. Toxoplasmosis, caused by a parasite, is another serious OI that frequently affects the brain, leading to neurological symptoms like headaches, confusion, and seizures. This parasitic infection commonly manifests when CD4 cell counts fall below 100 cells/mm³.
Cryptococcosis is a fungal infection that often impacts the lungs or brain, causing conditions like meningitis, an inflammation of the membranes surrounding the brain and spinal cord. It is a leading cause of death among people with HIV/AIDS in some parts of the world, particularly when CD4 counts are below 100 cells/mm³. Cytomegalovirus (CMV) retinitis, a viral infection, is a cause of vision loss and can lead to blindness by damaging the retina. This viral infection becomes active when CD4 cell counts drop below 50 cells/mm³.
Another bacterial infection is Mycobacterium avium complex (MAC), which can cause a life-threatening, disseminated infection throughout the body. Symptoms include fever, night sweats, weight loss, and abdominal pain. MAC is particularly prevalent in individuals with low CD4 counts, below 50 cells/mm³.
AIDS-Related Malignancies
The compromised immune system in AIDS increases the risk of developing certain cancers, known as AIDS-related malignancies. The immune system normally identifies and eliminates cancerous cells or controls cancer-causing viruses. When this surveillance fails, these specific cancers can emerge.
Kaposi’s sarcoma (KS) is a type of cancer that forms lesions on the skin, in the mouth, and can affect internal organs like the lungs and digestive tract. It is associated with human herpesvirus 8 (HHV-8) and is considered an AIDS-defining condition. Non-Hodgkin lymphoma (NHL) is another cancer that starts in white blood cells and can develop in various parts of the body, including the brain and spinal fluid.
Invasive cervical cancer, caused by the human papillomavirus (HPV), is also more common and often more aggressive in women with AIDS. The immune response struggles to suppress the HPV infection, allowing abnormal cells to proliferate.
Other Severe Manifestations
Beyond infections and cancers, AIDS can lead to other severe conditions that impact an individual’s health and quality of life.
AIDS Wasting Syndrome is characterized by involuntary weight loss exceeding 10% of body weight, often accompanied by chronic diarrhea, weakness, or fever. This complex condition involves both fat and muscle loss and is not solely attributable to other infections. The body enters a hypermetabolic state, where it burns more calories than it takes in, contributing to this decline.
HIV-associated neurocognitive disorder (HAND), previously known as AIDS dementia complex, encompasses a spectrum of cognitive, motor, and behavioral impairments. In its severe form, HIV-associated dementia (HAD) can cause memory loss, difficulty concentrating, problems with speech, and a decline in motor skills. This condition results from HIV affecting the brain directly, rather than through opportunistic infections, causing inflammation and damage to brain cells. HIV-associated nephropathy (HIVAN) is a kidney disease that can progress to kidney failure. It is characterized by specific kidney damage and is common in individuals with high viral loads and low CD4 counts.