Acquired Immunodeficiency Syndrome (AIDS - HIV)
Overview
Plain-Language Overview
Acquired Immunodeficiency Syndrome (AIDS - HIV) is a condition caused by the human immunodeficiency virus that attacks the body's immune system, specifically targeting CD4+ T cells. This weakens the body's ability to fight infections and certain cancers. As the immune system becomes severely damaged, people with AIDS become vulnerable to opportunistic infections and illnesses that a healthy immune system would normally control. The disease primarily affects the immune system, leading to progressive immune failure. Without treatment, AIDS can be life-threatening due to these infections and complications.
Clinical Definition
Acquired Immunodeficiency Syndrome (AIDS - HIV) is a chronic, progressive condition caused by infection with the human immunodeficiency virus (HIV), a retrovirus that targets and destroys CD4+ T lymphocytes, leading to profound immunosuppression. The hallmark of AIDS is a critically low CD4+ T cell count (usually <200 cells/μL) or the presence of specific opportunistic infections or AIDS-defining malignancies such as Kaposi sarcoma or Pneumocystis jirovecii pneumonia. The virus integrates into host DNA via the enzyme reverse transcriptase, causing persistent infection and immune system decline. The clinical significance lies in the increased susceptibility to life-threatening infections and cancers due to the loss of cell-mediated immunity. AIDS represents the most advanced stage of HIV infection and requires prompt diagnosis and management.
Inciting Event
Exposure to infected bodily fluids such as blood, semen, vaginal secretions, or breast milk.
Initial infection typically occurs via mucosal surfaces during sexual contact.
Needle-stick injury or sharing of contaminated injection equipment.
Vertical transmission from an HIV-positive mother to her child.
Rarely, transmission through blood transfusion with infected blood products.
Latency Period
The acute retroviral syndrome occurs 2-4 weeks after initial infection.
Clinical latency phase can last several years with gradual CD4+ decline.
Progression to AIDS typically occurs within 8-10 years without treatment.
Opportunistic infections emerge as CD4+ count falls below 200 cells/mm³.
Latency duration varies based on viral strain, host genetics, and treatment.
Diagnostic Delay
Early symptoms are often nonspecific and mistaken for common viral illnesses.
Lack of routine HIV screening in asymptomatic individuals delays diagnosis.
Stigma and fear may prevent patients from seeking timely testing.
Misattribution of symptoms to other chronic infections or malignancies.
Limited access to healthcare and diagnostic facilities in resource-poor settings.
Clinical Presentation
Signs & Symptoms
Fever, night sweats, and weight loss as constitutional symptoms of HIV infection.
Chronic diarrhea due to opportunistic gastrointestinal infections.
Oral thrush and esophagitis from Candida albicans overgrowth.
Progressive cognitive decline or focal neurologic signs indicating CNS involvement.
Recurrent bacterial infections due to immunodeficiency.
History of Present Illness
Initial presentation may include fever, lymphadenopathy, rash, and pharyngitis during acute infection.
Asymptomatic period follows with gradual onset of weight loss, chronic diarrhea, and night sweats.
Development of opportunistic infections such as Pneumocystis jirovecii pneumonia or Candida esophagitis.
Neurologic symptoms like memory loss, confusion, or focal deficits may appear in advanced disease.
Patients often report recurrent infections and persistent fatigue as immunodeficiency worsens.
Past Medical History
History of sexually transmitted infections increases suspicion for HIV.
Previous blood transfusions or organ transplants before screening implementation.
Intravenous drug use with shared needles is a significant risk factor.
Prior episodes of opportunistic infections or unusual malignancies suggest immunodeficiency.
Lack of prior HIV testing or incomplete antiretroviral therapy adherence.
Family History
No direct hereditary transmission, but vertical transmission from mother to child is critical.
Family members may share risk behaviors increasing exposure likelihood.
Genetic factors such as CCR5-Δ32 mutation can confer resistance in some individuals.
No familial syndromes directly cause AIDS but familial clustering of risk factors occurs.
Awareness of family members with HIV infection can prompt earlier testing and diagnosis.
Physical Exam Findings
Generalized lymphadenopathy often present in early HIV infection.
Oral candidiasis with white plaques that can be scraped off the mucosa.
Kaposi sarcoma lesions appearing as violaceous plaques or nodules on the skin or mucosa.
Cachexia and wasting syndrome in advanced AIDS due to chronic infection and malnutrition.
Neurologic deficits such as focal weakness or cognitive impairment in HIV-associated neurocognitive disorders.
Diagnostic Workup
Diagnostic Criteria
Diagnosis of AIDS is established by confirming HIV infection through serologic tests such as ELISA followed by confirmatory Western blot or nucleic acid testing. AIDS is defined by a CD4+ T cell count below 200 cells/μL or the presence of one or more AIDS-defining illnesses including certain opportunistic infections or malignancies. Clinical history and laboratory evaluation of immune status are essential to differentiate between HIV infection and progression to AIDS.
Pathophysiology
Key Mechanisms
HIV infects and depletes CD4+ T cells, leading to progressive immunodeficiency.
Reverse transcriptase converts viral RNA into DNA, enabling integration into host genome.
Chronic immune activation causes immune exhaustion and lymphoid tissue destruction.
Loss of cell-mediated immunity predisposes to opportunistic infections and malignancies.
Viral mutation leads to immune evasion and resistance to antiretroviral therapy.
| Involvement | Details |
|---|---|
| Organs | Lymph nodes are critical sites of HIV replication and immune cell interaction. |
Brain can be affected by HIV-associated neurocognitive disorders due to viral invasion and inflammation. | |
Lungs are commonly involved in opportunistic infections in AIDS patients. | |
| Tissues | Lymphoid tissue is a major site of HIV replication and CD4+ T cell depletion. |
Gut-associated lymphoid tissue (GALT) is an early and significant site of CD4+ T cell loss in HIV infection. | |
| Cells | CD4+ T cells are the primary target of HIV infection and their depletion leads to immunodeficiency. |
Macrophages serve as reservoirs for HIV and contribute to viral persistence and dissemination. | |
Dendritic cells facilitate HIV transmission to T cells and initiate immune responses. | |
| Chemical Mediators | Cytokines such as IL-2 and TNF-alpha are dysregulated in HIV infection, contributing to immune activation and pathogenesis. |
Reverse transcriptase is the viral enzyme targeted by multiple antiretroviral drugs to inhibit HIV replication. | |
Integrase is a viral enzyme essential for integration of HIV DNA into the host genome and a key drug target. |
Treatments
Pharmacological Treatments
Nucleoside Reverse Transcriptase Inhibitors (NRTIs)
- Mechanism:
Inhibit HIV reverse transcriptase by acting as nucleoside analogs causing chain termination during viral DNA synthesis.
- Side effects:
Lactic acidosis
Hepatotoxicity
Bone marrow suppression
- Clinical role:
First-line
Non-Nucleoside Reverse Transcriptase Inhibitors (NNRTIs)
- Mechanism:
Bind directly to HIV reverse transcriptase causing allosteric inhibition of viral DNA synthesis.
- Side effects:
Rash
Hepatotoxicity
Neuropsychiatric symptoms
- Clinical role:
First-line
Protease Inhibitors (PIs)
- Mechanism:
Inhibit HIV protease, preventing cleavage of viral polyproteins and production of mature infectious virions.
- Side effects:
Hyperlipidemia
Insulin resistance
Lipodystrophy
- Clinical role:
First-line
Integrase Strand Transfer Inhibitors (INSTIs)
- Mechanism:
Block HIV integrase enzyme, preventing integration of viral DNA into host genome.
- Side effects:
Insomnia
Headache
Elevated creatine kinase
- Clinical role:
First-line
CCR5 Antagonists
- Mechanism:
Block CCR5 co-receptor on host cells, preventing HIV entry.
- Side effects:
Hepatotoxicity
Respiratory infections
- Clinical role:
Second-line
Fusion Inhibitors
- Mechanism:
Prevent fusion of HIV envelope with host cell membrane by binding gp41.
- Side effects:
Injection site reactions
Increased risk of bacterial pneumonia
- Clinical role:
Second-line
Non-pharmacological Treatments
Use of condoms and safe sex practices to prevent HIV transmission.
Regular monitoring of CD4 count and viral load to guide therapy and detect treatment failure.
Nutritional support and management of opportunistic infections to improve quality of life.
Counseling and psychosocial support to enhance adherence to antiretroviral therapy.
Prevention
Pharmacological Prevention
Pre-exposure prophylaxis (PrEP) with tenofovir/emtricitabine to prevent HIV acquisition.
Post-exposure prophylaxis (PEP) initiated within 72 hours after potential HIV exposure.
Antiretroviral therapy (ART) to suppress viral replication and prevent disease progression.
Prophylactic antibiotics such as trimethoprim-sulfamethoxazole to prevent Pneumocystis jirovecii pneumonia.
Vaccination against preventable infections like pneumococcus and influenza.
Non-pharmacological Prevention
Consistent condom use to reduce sexual transmission of HIV.
Needle exchange programs to prevent transmission among intravenous drug users.
Routine HIV screening in high-risk populations for early detection and treatment.
Safe blood transfusion practices to avoid HIV transmission.
Counseling and education on risk reduction and adherence to therapy.
Outcome & Complications
Complications
Opportunistic infections such as Pneumocystis jirovecii pneumonia and toxoplasmosis.
AIDS-defining malignancies including Kaposi sarcoma and non-Hodgkin lymphoma.
HIV-associated neurocognitive disorders ranging from mild impairment to dementia.
Immune reconstitution inflammatory syndrome (IRIS) after initiation of antiretroviral therapy.
Wasting syndrome with severe weight loss and muscle atrophy.
| Short-term Sequelae | Long-term Sequelae |
|---|---|
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Differential Diagnoses
Acquired Immunodeficiency Syndrome (AIDS - HIV) versus Primary Immunodeficiency Disorders
Acquired Immunodeficiency Syndrome (AIDS - HIV) | Primary Immunodeficiency Disorders |
|---|---|
Usually presents in adulthood after years of asymptomatic HIV infection | Typically presents in infancy or early childhood |
Characterized by progressive depletion of CD4+ T cells | Often involves congenital defects in B cells, T cells, or phagocytes with variable lymphocyte counts |
Positive HIV antibody/antigen test and detectable HIV RNA viral load | Genetic testing reveals mutations in immune-related genes |
Acquired Immunodeficiency Syndrome (AIDS - HIV) versus Acute Viral Infections (e.g., Infectious Mononucleosis)
Acquired Immunodeficiency Syndrome (AIDS - HIV) | Acute Viral Infections (e.g., Infectious Mononucleosis) |
|---|---|
Chronic progressive immunodeficiency without spontaneous resolution | Self-limited illness lasting weeks with spontaneous resolution |
Lymphopenia with marked CD4+ T cell depletion | Lymphocytosis with atypical lymphocytes |
Positive HIV antibody/antigen test and HIV RNA PCR | Positive heterophile antibody test or EBV serology |
Acquired Immunodeficiency Syndrome (AIDS - HIV) versus Chronic Corticosteroid Use
Acquired Immunodeficiency Syndrome (AIDS - HIV) | Chronic Corticosteroid Use |
|---|---|
No history of immunosuppressive medication use; risk factors include unprotected sex or IV drug use | History of prolonged corticosteroid therapy or immunosuppressive drugs |
Selective CD4+ T cell depletion due to viral infection | Generalized immunosuppression affecting multiple immune cells including neutrophils and lymphocytes |
Requires antiretroviral therapy for immune restoration | Immunosuppression improves with tapering corticosteroids |
Acquired Immunodeficiency Syndrome (AIDS - HIV) versus Tuberculosis (TB) Infection
Acquired Immunodeficiency Syndrome (AIDS - HIV) | Tuberculosis (TB) Infection |
|---|---|
Caused by HIV, a retrovirus | Caused by Mycobacterium tuberculosis |
Imaging may show opportunistic infections or lymphadenopathy without classic TB cavitation | Chest imaging shows upper lobe cavitary lesions or miliary pattern |
Positive HIV antibody/antigen test and HIV RNA PCR | Positive acid-fast bacilli smear or culture |
Acquired Immunodeficiency Syndrome (AIDS - HIV) versus Leukemia or Lymphoma
Acquired Immunodeficiency Syndrome (AIDS - HIV) | Leukemia or Lymphoma |
|---|---|
Decreased CD4+ T cells without malignant cells | Presence of abnormal or immature white blood cells (blasts) in peripheral blood or bone marrow |
Chronic immunodeficiency with opportunistic infections over months to years | Rapidly progressive with systemic symptoms like weight loss and night sweats |
Positive HIV serology and viral load without malignant cells | Bone marrow biopsy showing malignant infiltration |