Acquired immunodeficiency syndrome (AIDS) results from infection with the human immunodeficiency virus (HIV), which primarily targets and destroys CD4+ T lymphocytes. Over time, this leads to severe immune deficiency, predisposing individuals to life-threatening opportunistic infections and malignancies. AIDS represents a major public health challenge worldwide.
Etiology and Pathogenesis
HIV is a single-stranded RNA virus belonging to the genus Lentivirus in the family Retroviridae. The virus exists in three variants: HIV-1, HIV-2, and HIV-0. HIV specifically targets CD4+ T cells through its envelope glycoprotein gp120, which binds to CD4 receptors, allowing the virus to enter and replicate within these cells. As replication progresses, destruction of CD4+ T cells intensifies, resulting in immune suppression and a weakened defense against various pathogens. In the AIDS stage, the CD4+ T cell count may drop below 200 cells/mm3. HIV is also capable of infecting monocytes and macrophages.
Stages of Disease
The disease progression is classified into three stages:
Acute Phase
This phase typically occurs within six months of HIV infection. Some individuals may experience mild, transient symptoms resembling a common cold, such as sore throat, fever, fatigue, sweating, nausea, vomiting, and diarrhea. These symptoms generally last 1–3 weeks before spontaneously resolving.
Asymptomatic Phase
This phase generally lasts 4–8 years. During this time, HIV continues to replicate, gradually impairing the immune system, and the CD4+ T cell count steadily declines. Symptoms such as lymphadenopathy may develop. Individuals in this phase remain infectious.
AIDS Phase
This final stage represents advanced disease. Immune function deteriorates entirely, leading to severe systemic illnesses, neurological complications (e.g., AIDS-related encephalopathy), opportunistic infections (caused by pathogens that do not typically infect immunocompetent individuals, such as viruses, fungi, mycobacteria, and protozoa), secondary malignancies (such as Kaposi sarcoma and non-Hodgkin lymphoma), and other complications. Death often results from secondary opportunistic infections, central nervous system disease, cachexia, or malignancies.
Clinical Manifestations
Head and neck lesions occur in 40%–70% of AIDS patients and include:
Ear Involvement
Kaposi sarcoma (KS) may occur in the external ear, presenting as multiple, idiopathic, hemorrhagic tumors that appear as purplish-red papules or nodules or as diffuse, infiltrative, hemorrhagic plaques. Pneumocystis jirovecii infection in the external ear often manifests as multinucleated cysts. Central nervous system or auditory nerve involvement may cause tinnitus, vertigo, sensorineural hearing loss, or facial paralysis. HIV may be isolated from middle ear effusion, while fungi, protozoa, viruses, or mycobacteria may also be cultured from middle ear exudates in cases of otitis media.
Nasal and Sinus Involvement
Secondary infections of the nasal and sinus mucosa may result in mucosal swelling, nasal obstruction, purulent rhinorrhea, or epistaxis. Herpes virus infections may cause large herpetic ulcers extending from the nasal vestibule to the nasal septum and outward to the nasal ala and surrounding facial areas. Kaposi sarcoma or lymphoma in the nasal region may also present with nasal obstruction, persistent foul-smelling rhinorrhea, or epistaxis. Examination may reveal purplish nodular tumors in the affected regions.
Oral and Pharyngeal Involvement
Candidiasis is the most common upper respiratory tract manifestation. Reports indicate that 42% of HIV-infected patients experience oral candidiasis, presenting as hairy leukoplakia on the lateral tongue, dorsal tongue, or buccal mucosa. These lesions are characterized by rough, white plaques a few millimeters thick that are adherent and difficult to scrape off, representing an early and specific sign of HIV infection. Within 16–31 months of follow-up, 48%–83% of affected patients may progress to AIDS. Kaposi sarcoma often occurs on the palate, buccal mucosa, gingiva, or posterior pharyngeal wall as elevated purplish nodules. Infections such as Kaposi sarcoma and candidiasis may also involve the larynx, leading to hoarseness, stridor, or airway obstruction. Severe cases may require tracheostomy.
Neck Involvement
Cervical lymphadenopathy is an early symptom, frequently observed in the posterior cervical triangle. Kaposi sarcoma may affect the skin of the head and neck and spread to the lymph nodes, causing rapid enlargement. Cervical masses should also be evaluated for non-Hodgkin lymphoma or mycobacterial infections. Fine-needle aspiration biopsy is useful for diagnosis and differential diagnosis. Viral infections may lead to parotid gland enlargement.
Diagnosis
The diagnosis is based on medical history, clinical manifestations, and laboratory test results.
Detailed Medical History
A thorough history includes information about same-sex activity, high-risk sexual behavior, intravenous drug use, and exposure to blood products.
Opportunistic Infections
Manifestations such as Pneumocystis jirovecii pneumonia and Kaposi sarcoma are key diagnostic indicators. Persistent low-grade fever, chronic diarrhea, weight loss, generalized lymphadenopathy, and candidiasis involving the oral and pharyngeal regions may serve as precursors to AIDS and warrant attention.
Indicators of Immune Deficiency: A reduced CD4+ T cell count is characteristic. According to the revised 1991 diagnostic criteria from the U.S. Centers for Disease Control and Prevention (CDC), a CD4+ T lymphocyte count of <200/μL confirms the diagnosis of AIDS. Additionally, a CD4+/CD8+ ratio of <1 can also indicate immune deficiency.
Laboratory Testing: Diagnostic methods include viral isolation and culture, antigen testing, antibody testing, and viral nucleic acid detection. Positive results from screening tests require confirmatory testing to eliminate false positives. HIV antibodies can typically be detected approximately two months after infection.
Treatment
Antiretroviral Drugs
Globally, six major categories and more than 30 antiretroviral drugs are available, including nucleoside reverse transcriptase inhibitors (NRTIs), non-nucleoside reverse transcriptase inhibitors (NNRTIs), protease inhibitors (PIs), integrase strand transfer inhibitors (INSTIs), fusion inhibitors (FIs), and CCR5 inhibitors. Five classes of antiretroviral drugs (including combination therapies) are commonly used: NRTIs, NNRTIs, PIs, INSTIs, and FIs. Zidovudine (AZT), an inhibitor of reverse transcriptase, suppresses HIV replication but has significant toxicity, including bone marrow suppression with prolonged use. Similar mechanisms of action are observed with drugs such as zalcitabine (DDC) and didanosine (DDI). Nevirapine (NVP) and delavirdine are NNRTIs that bind non-competitively to HIV reverse transcriptase, reducing viral replication. The "cocktail therapy" approach combines protease inhibitors with multiple antiretroviral drugs, significantly improving AIDS control rates.
Immunomodulatory Drugs
Alpha-interferon exhibits antiviral replication inhibition and immunoregulatory activity, and its early use may reduce opportunistic infections. Agents such as interleukin-2 (IL-2), granulocyte-macrophage colony-stimulating factor (GM-CSF), and granulocyte colony-stimulating factor (G-CSF) may increase peripheral white blood cell counts, enhancing immune defense and decreasing opportunistic infections.
Prevention and Treatment of Opportunistic Infections
The occurrence of opportunistic infections can be roughly predicted based on CD4+ T cell counts, and prophylactic treatment may lower the risk of Pneumocystis jirovecii pneumonia. Treatments for different opportunistic infections include:
- For protozoal infections: sulfamethoxazole-trimethoprim (SMZ-TMP) or pentamidine.
- For viral infections: acyclovir or foscarnet sodium.
- For fungal infections: amphotericin B or imidazole antifungal drugs.
- For bacterial infections: antibiotics are selected based on culture and drug sensitivity results.
Other Treatments
This includes treatment for malignancies, supportive care, and symptomatic management.
Prevention
Improving public awareness about AIDS prevention, including knowledge of transmission routes, clinical manifestations, and protection measures, is essential.
Strengthening screening and quarantine measures is vital. Blood and blood products must undergo HIV testing, and AIDS prevention efforts at ports of entry should be intensified.
HIV-positive individuals are prohibited from donating blood, organs, or other tissues. Women living with HIV should avoid pregnancy.
Sexual contact with HIV-positive individuals, AIDS patients, or high-risk populations should be avoided, and condom use is encouraged.
Personal items such as toothbrushes and razors that may become contaminated with blood should not be shared.
Disposable medical injection equipment should be used whenever possible, and reusable equipment should undergo strict disinfection protocols.
Healthcare workers should adopt protective measures when exposed to blood or bodily fluids of HIV-positive individuals or AIDS patients.
Efforts to combat drug abuse, prostitution, and commercial sex must be intensified, and long-term monitoring should focus on high-risk populations.