ACRN Opportunistic Infections Management 1 — Questions and Answers
Question 1: At what CD4 count threshold is prophylaxis for Pneumocystis jirovecii pneumonia (PCP) recommended?
- Less than 500 cells/mm³
- Less than 350 cells/mm³
- Less than 200 cells/mm³ (Correct answer)
- Less than 100 cells/mm³
Correct answer: Less than 200 cells/mm³
PCP prophylaxis is initiated when the CD4 count falls below 200 cells/mm³, the threshold at which cellular immunity is severely compromised.
Question 2: A patient with HIV presents with fever, dry cough, and hypoxia. Chest X-ray shows bilateral interstitial infiltrates and the CD4 count is 150 cells/mm³. Which opportunistic infection is most likely?
- Mycobacterium avium complex (MAC)
- Pneumocystis jirovecii pneumonia (PCP) (Correct answer)
- CMV pneumonitis
- Cryptococcal pneumonia
Correct answer: Pneumocystis jirovecii pneumonia (PCP)
PCP classically presents with bilateral interstitial infiltrates, dry cough, and progressive hypoxia in patients with CD4 < 200 cells/mm³.
Question 3: Mycobacterium avium complex (MAC) most commonly occurs when the CD4 count drops below:
- 200 cells/mm³
- 150 cells/mm³
- 100 cells/mm³
- 50 cells/mm³ (Correct answer)
Correct answer: 50 cells/mm³
MAC disseminated disease typically develops when the CD4 count falls below 50 cells/mm³, making it one of the latest-stage opportunistic infections.
Question 4: A patient with HIV and CD4 of 45 cells/mm³ presents with headache, stiff neck, and altered mental status. CSF India ink preparation reveals encapsulated yeast. What is the diagnosis?
- Toxoplasma encephalitis
- CMV encephalitis
- Cryptococcal meningitis (Correct answer)
- Progressive multifocal leukoencephalopathy
Correct answer: Cryptococcal meningitis
India ink staining identifying encapsulated yeast in CSF is a classic diagnostic finding for Cryptococcal meningitis caused by Cryptococcus neoformans.
Question 5: Toxoplasma gondii encephalitis typically occurs in HIV patients when the CD4 count falls below:
- 200 cells/mm³
- 150 cells/mm³
- 100 cells/mm³ (Correct answer)
- 50 cells/mm³
Correct answer: 100 cells/mm³
Toxoplasma encephalitis generally develops when the CD4 count drops below 100 cells/mm³, placing it at a CD4 threshold between PCP and MAC.
Question 6: Which drug is the preferred first-line prophylaxis for PCP in HIV patients with CD4 < 200 cells/mm³?
- Dapsone
- Atovaquone
- Trimethoprim-sulfamethoxazole (TMP-SMX) (Correct answer)
- Pentamidine
Correct answer: Trimethoprim-sulfamethoxazole (TMP-SMX)
TMP-SMX (one double-strength tablet daily) is the preferred PCP prophylaxis due to superior efficacy and the added benefit of covering Toxoplasma gondii.
Question 7: CMV retinitis is an AIDS-defining illness that most commonly occurs when CD4 count falls below:
- 200 cells/mm³
- 150 cells/mm³
- 100 cells/mm³
- 50 cells/mm³ (Correct answer)
Correct answer: 50 cells/mm³
CMV retinitis is typically seen in severely immunocompromised patients with CD4 < 50 cells/mm³ and can lead to irreversible vision loss if untreated.
ACRN Opportunistic Infections Management 1
At what CD4 count threshold is prophylaxis for Pneumocystis jirovecii pneumonia (PCP) recommended?