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Acquired Immunodeficiency Syndrome (AIDS)
Acquired immunodeficiency syndrome (AIDS) is the advanced stage of infection caused by the human immunodeficiency virus (HIV). It is characterized by progressive destruction of cell-mediated immunity, particularly CD4⁺ T lymphocytes, which leads to opportunistic infections, malignancies, and systemic complications. A diagnosis of AIDS is made in a person with confirmed HIV infection when the CD4 cell count falls below 200 cells/mm³ (or <14% of total lymphocytes) or when specific aids-defining conditions are present, even if symptoms otherwise minimal.< />pan>
In the United States, approximately 1.2 million people are living with HIV, and a subset have progressed to AIDS. New diagnoses occur disproportionately among Black/African American and Latino/Hispanic populations, and the majority of cases are among men, particularly gay, bisexual, and other men who have sex with men (MSM). The most commonly affected age group is 25 to 59 years. Although there is no proven hereditary predisposition, individuals with certain genetic mutations, such as CCR5 deletions, are less susceptible to HIV infection and may progress more slowly to AIDS. Without treatment, HIV can also be transmitted vertically from mother to fetus or neonate.
Clinical presentation varies widely. Some individuals are asymptomatic, while others present with nonspecific symptoms such as fever, weight loss, anorexia, and fatigue. As immune function declines, patients develop opportunistic infections involving the lungs (e.g., Pneumocystis jirovecii pneumonia, tuberculosis), central nervous system (e.g., toxoplasmosis, cryptococcosis, progressive multifocal leukoencephalopathy), gastrointestinal tract (e.g., chronic cryptosporidiosis, CMV colitis), eyes (e.g., CMV retinitis), and skin. AIDS-related malignancies include Kaposi sarcoma, primary CNS lymphoma, invasive cervical cancer, and high-grade B-cell non-Hodgkin lymphomas.
HIV infection is caused by HIV-1 (most common worldwide) or HIV-2 (less common, mainly in West Africa). Transmission occurs through sexual contact, needle sharing during injection drug use, transfusion of contaminated blood products, and vertical transmission from mother to child during pregnancy, delivery, or breastfeeding.
Diagnosis relies on HIV antibody/antigen testing, followed by assessment of immune and virologic status. Key laboratory studies include CD4 cell count to gauge immunodeficiency and HIV viral load (HIV RNA PCR) to guide therapy and monitor treatment response. Additional evaluation commonly includes screening for sexually transmitted infections, hepatitis A, B, and C, syphilis, toxoplasmosis, and tuberculosis. Imaging studies such as chest radiography or CT and brain MRI or CT are used when pulmonary or neurologic symptoms suggest opportunistic disease.
The cornerstone of management is early and sustained antiretroviral therapy (ART), which should be initiated in all patients with HIV regardless of CD4 count. ART suppresses viral replication, allows immune recovery, reduces opportunistic infections, and dramatically improves survival. Modern regimens typically combine two nucleoside reverse transcriptase inhibitors with an integrase inhibitor, and are generally well tolerated. In addition to ART, patients with AIDS often require prophylactic therapy to prevent infections such as Pneumocystis jirovecii pneumonia and Mycobacterium avium complex until immune reconstitution occurs.
Nonpharmacologic management includes maintaining adequate nutrition, practicing safe sex, avoiding needle sharing, and minimizing exposure to opportunistic pathogens. Vaccinations against influenza, pneumococcus, hepatitis A and B, meningococcus, COVID-19, and Tdap are recommended, while live vaccines are generally avoided in patients with advanced immunosuppression.
The prognosis of HIV/AIDS has changed dramatically. With consistent access to ART and expert medical follow-up, HIV is now a chronic, manageable condition, and many patients enjoy near-normal life expectancy and quality of life. All individuals diagnosed with HIV or AIDS should be referred to clinicians experienced in HIV care to ensure optimal treatment, monitoring, and prevention of complications.
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