Overview
Definition
Human Immunodeficiency Virus (HIV) is a retrovirus that attacks the immune system, specifically CD4+ T cells. AIDS (Acquired Immunodeficiency Syndrome) is the most advanced stage.
Epidemiology
Global pandemic. Transmitted via sexual contact, blood (IV drug use), and vertically (mother-to-child).
Etiology & Risk Factors
- HIV-1 (most common globally) and HIV-2 (mostly in West Africa)
- Virus uses reverse transcriptase to integrate its RNA into the host cell's DNA, leading to progressive CD4 cell destruction.
Clinical Symptoms
- Acute Retroviral Syndrome (2-4 weeks post-infection): Mononucleosis-like symptoms (fever, lymphadenopathy, sore throat, maculopapular rash)
- Clinical Latency (can last years): Generally asymptomatic
- AIDS (CD4 < 200 cells/µL): Opportunistic infections, severe weight loss (HIV wasting syndrome), Kaposi's sarcoma
Clinical Approach
Diagnosis
- Screening: 4th Generation HIV-1/2 Antigen/Antibody immunoassay (detects p24 antigen and HIV antibodies)
- Confirmation: HIV-1/HIV-2 antibody differentiation assay
- Monitoring: CD4+ count (assesses immune function) and HIV RNA viral load (assesses treatment efficacy)
Management
- Antiretroviral Therapy (ART) for ALL patients regardless of CD4 count
- Standard regimen: 2 Nucleoside Reverse Transcriptase Inhibitors (NRTIs, e.g., Tenofovir/Emtricitabine) PLUS an Integrase Strand Transfer Inhibitor (INSTI, e.g., Dolutegravir or Bictegravir)
- Prophylaxis: Bactrim for PCP pneumonia when CD4 < 200, Azithromycin for MAC when CD4 < 50
Complications
- Opportunistic Infections: Pneumocystis jirovecii pneumonia (PCP), Toxoplasmosis, Cryptococcal meningitis, Cytomegalovirus (CMV) retinitis
- Malignancies: Primary CNS Lymphoma, Kaposi Sarcoma, Cervical Cancer