Illustration of HIV.
Image from: Wikipedia
I admit, most of the general medicine categories will be rather broad topics. Truth be told, the main things you need to know about HIV and AIDS are more geared towards the opportunistic illnesses that arise from the immunodeficient state present in the late stages. You'll likely see some of those opportunistic conditions pop up in other sections, as we work through each article.
Key Facts
HIV retinopathy. HIV retinopathy is the most common ocular manifestation of HIV, and is in the differential diagnosis of multiple cotton-wool spots.
Image from: AAO
- HIV infection results in a decrease in T-helper-inducer cell and macrophage populations.
- B-lymphocytes are hyperfunctioning (cranking out antibodies in response to infection), but there are few T-helper cells, the entire immune response is attenuated.
- The CCR5 gene encodes for a T-cell surface receptor that allows HIV to enter the cell; some people have a defect in this gene and thus have a natural immunity to HIV.
- HIV is diagnosed by 2 ELISAs (screening) + a Western blot or IFA (confirmatory). An HIV p24 antigen or HIV-1 RNA PCR test may yield earlier positive results.
- The following vaccines are contraindicated in HIV patients:
- Live-attenuated influenza virus
- Varicella zoster virus
- Oral polio virus
- Smallpox
- Typhoid
- Yellow fever
- MMR (specifically the measles vaccine)
- 10% of HIV patients with a previous history of CMV retinitis starting on HAART therapy can develop immune recovery uveitis.
- The most common ocular finding in HIV is HIV retinopathy, which is a microangiopathy characterized by retinal hemorrhages and multiple cotton-wool spots. It is present in 70% of patients.
- CMV retinitis, herpes zoster infection, and Toxoplasmosis infections are the most common causes of vision loss in AIDS.
- HIV is found in tears, conjunctival and corneal epithelium, aqueous, retinal vascular endothelium, and retina. As a result, HIV infection is a contraindication for donating corneas.
- To disinfect instruments, instruments should be soaked for 5-10 minutes in one of the following solutions, then rinsed with tap water and dried:
- 3% hydrogen peroxide
- 1/10 dilution of bleach (5000 ppm chlorine)
- 70% ethanol
- 70% isopropanol
- Test contact lenses can be disinfected with hydrogen peroxide or heat.
Opportunistic Infections
CD4 Count (cells/μL)
200-500
150-200
< 100
Opportunistic Diseases
- Oral candidiasis
- Kaposi sarcoma
- Lymphoma
- HZO
- Disseminated TB
- Pneumocystis: most common opportunistic pneumonia in AIDS
- Toxoplasmosis
- Mycobacterium avium complex
- CMV (CD4 < 50): most common opportunistic infection in AIDS
Sample Questions (answers at the bottom of the page)
- Which of these statements best summarizes the lymphocyte activity in HIV infection?
A. B-lymphocyte activity is high, T-lymphocyte activity is high
B. B-lymphocyte activity is high, T-lymphocyte activity is low
C. B-lymphocyte activity is low, T-lymphocyte activity is high
D. B-lymphocyte activity is low, T-lymphocyte activity is low
- Which of the following tests will yield the fastest result for HIV testing?
A. ELISA + immunofluorescence assay
B. ELISA + Western blot
C. HIV PCR
D. No significant difference in time to diagnosis
- What is the most common ocular finding in HIV?
A. CMV retinitis
B. Toxoplasma chorioretinitis
C. Peripheral outer retinal necrosis
D. Cotton-wool spots
- What is the most common opportunistic infection in AIDS?
A. CMV retinitis
B. Pneumocystis pneumonia
C. Toxoplasma chorioretinitis
D. Oral candidiasis
- What is the most appropriate method for disinfecting a Goldmann applanation tip after measuring intraocular pressure on an HIV-positive patient?
A. Soak the tip in 3% hydrogen peroxide for 30 minutes, rinse with water, then dry
B. Rinse with water, soak the tip in 1/10 dilution of bleach for 5 minutes, then dry
C. Soak the tip in isopropyl alcohol for 3 minutes, rinse with water, then dry
D. Wipe the tip with isopropyl alcohol vigorously for 3 minutes, rinse with water, then dry
- How far does the CD4 count need to decrease before there is a risk for developing mycobacterium avium complex?
A. 50 cells/μL
B. 100 cells/μL
C. 200 cells/μL
D. 500 cells/μL
Sample Question Answers
- B. In HIV infection, B cells are hyperfunctioning, but there is minimal T cell response.
- C. HIV PCR and HIV p24 antigen may speed up positive diagnosis time. Typically the ELISA for HIV is run twice, followed by a confirmatory test of either a Western blot or an immunofluorescence assay (IFA).
- D. HIV retinopathy is the most common ocular manifestation of HIV, seen in up to 70% of patients. It can look very similar to diabetic retinopathy and other microangiopathies, and should be considered in the differential diagnosis of multiple cotton-wool spots.
- A. CMV retinitis remains the most common opportunistic infection in AIDS. Patients are at a higher risk for CMV retinitis when their CD4 count is less than 50 cells/μL. Pneumocystis is the most common opportunistic pneumonia in AIDS.
- C. Although the risk of HIV transmission is fairly low with ophthalmic devices, care should be taken to minimize the risk of transmission to other patients, as HIV has been detected in tears, cornea, and aqueous. The general rule for disinfecting is complete immersion in a strong cleaning solution (3% hydrogen peroxide, 1/10 dilution of bleach, 70% ethanol, or 70% isopropanol) for 3-5 minutes, followed by a rinse with water, then dried, prior to use. Use of a device prior to water rinse increases the risk of tissue damage from the cleaning solution.
- B. Mycobacterium avium complex (MAC) may present when the CD4 count falls below 100 cells/μL.
References and Additional Reading
- Basic and Clinical Science Course, Section 1: Update on General Medicine. American Academy of Ophthalmology, 2017-2018 edition.
Do you have any suggestions on what else might be important to know about HIV? Do you have any tips for helping to remember all of this information? Do you have any requests for specific topics to cover? Leave a comment or send us a message!