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Author Anonymous (Edited by Ayokunle Olubaniyi and Alison Leibowitz)
Exam Type USMLE Step 2 CK
Main Category Internal medicine
Sub Category Infectious Disease, Infectious Disease
Prompt A 23-year-old HIV-positive woman recently started on HAART therapy comes to the health center for a checkup. Her CD4 count has been decreasing over the last 5 months, although she remains asymptomatic. Physical examination is unremarkable but her current CD4 count is 192 cells/mm3.

Which of the following prophylactic medications is most appropriate at this time?

Answer A [[AnswerA::Isoniazid and rifampin.]]
Answer A Explanation [[AnswerAExp::These are used in the treatment of tuberculosis.]]
Answer B [[AnswerB::Penicillin G]]
Answer B Explanation This is usually used to treat syphilis in HIV-positive patients. It is not used as a prophylactic medication against PCP.
Answer C [[AnswerC::Valacyclovir.]]
Answer C Explanation [[AnswerCExp::Valaciclovir is effective in preventing cytomegalovirus among patients with HIV.]]
Answer D Trimethoprim/sulfamethoxazole
Answer D Explanation This is the drug of choice for the prevention of PCP among HIV-positive patients with CD4+ T cell count of <200 cells/µLcells/mm3.
Answer E Ketoconazole.
Answer E Explanation [[AnswerEExp::This is effective in treating opportunistic fungal infections e.g., candidiasis, among HIV-positive patients.]]
Right Answer D
Explanation [[Explanation::Pneumocystis pneumonia (PCP) is relatively rare in people with normal immune systems but common among people with weakened immune systems, such as premature or severely malnourished children, the elderly, and especially AIDS patients, in whom it is most commonly observed today. PCP can also develop in patients who are taking immunosuppressive medications (e.g. patients who have undergone solid organ transplantation) and in patients who have undergone bone marrow transplantation.

HIV-infected adults and adolescents, including pregnant women and those on antiretroviral therapy, should receive chemoprophylaxis against PCP if they have a CD4+ count of <200 cells/µL (AI). The drug of choice is trimethoprim/sulfamethoxazole (TMP-SMX).
Educational Objective: PCP is an opportunistic infection commom among HIV-positive patients with a CD4+ T cell count of <200 cells/mm3. The drug of choice is TMP-SMX.
References: "The risk of Pneumocystis carinii pneumonia among men infected with human immunodeficiency virus type 1. Multicenter AIDS Cohort Study Group". N. Engl. J. Med. 322 (3): 161–5. doi:10.1056/NEJM199001183220304

"Risk factors for primary Pneumocystis carinii pneumonia in human immunodeficiency virus-infected adolescents and adults in the United States: reassessment of indications for chemoprophylaxis". J. Infect. Dis. 178 (4): 1126–32.


Approved No
Keyword HIV, HIV opportunistic infections, Pneumocystis carinii prophylaxis
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