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{{WBRQuestion
{{WBRQuestion
|QuestionAuthor={{Rim}}
|QuestionAuthor={{YD}} (Reviewed by {{YD}})
|ExamType=USMLE Step 1
|ExamType=USMLE Step 1
|MainCategory=Microbiology
|MainCategory=Microbiology
Line 21: Line 21:
|MainCategory=Microbiology
|MainCategory=Microbiology
|SubCategory=Infectious Disease
|SubCategory=Infectious Disease
|Prompt=A 44 year old man with history of multiple unprotected sexual encounters was found to have a positive HIV ELISA during a local screening campaign. He was referred to an HIV clinic where he was advised to monitor his CD4 counts once every month. A trend of his CD4 counts for past 10 months are shown below. At which of the following CD4 values would you advise the patient to receive azithromycin prophylaxis?
|Prompt=A 44-year-old man with history of multiple unprotected sexual encounters was found to have a positive HIV ELISA during a local screening campaign. He was referred to an HIV clinic where he was advised to regularly monitor his CD4 counts. The patient admits that he has been non-compliant with his anti-retroviral therapy. A trend of his CD4 counts for the past 10 months are illustrated in the graph below. At which CD4 values should the physician first advise the prophylactic administration of azythromycin?
 
[[Image:CD4count.jpg|600px]]
[[Image:CD4count.jpg|600px]]
|Explanation=Azithromycin is used in patients with HIV who progressed to AIDS with a CD4 count lower than 50 cells/mL for the prophylaxis for disseminated mycobacterium avium complex (MAC) infections. Organisms of the Mycobacterium avium complex (MAC) are Mycobacterium avium and intracellulare. They are ubiquitous in the environment and have many modes of transmission thus justifying the need for prophylaxis. However, it is important to note that MAC are not communicable. The table below summarizes the AIDS associated illnesses and the corresponding CD4 counts at which they are observed.
|Explanation=Azithromycin is a macrolide antibiotic that binds to 23S rRNA of the 50S ribosomal subunit and inhibits protein synthesis via inhibition of translocation. Azythromycin may be administered to treat cases of atypical pneumonias and gram-positive cocci infections in patients allergic to penicillin. In addition, azythromycin may be administered prophylactically to HIV-positive patients whose CD4 counts are below 50 cells/mm3 to prevent the development of disseminated Mycovacterium Avium Complex (MAC). Mycobacterium avium complex (MAC) includes the following organisms: ''M. avium'' and ''M. intracellulare''.  
 


The table below summarizes the AIDS associated illnesses and the corresponding CD4 counts at which they are observed.
The following table summarizes the association between opportunistic infections and CD4 counts in HIV patients.
[[Image:AIDS_illnesses_CD4.jpg|500px]]
[[Image:AIDS_illnesses_CD4.jpg|500px]]
|AnswerA=A
|AnswerA=A
|AnswerAExp=Usually a CD4>500 cells/mL is considered normal does not present with AIDS associated illness.
|AnswerAExp=CD4 > 500 cells/mm3 is considered normal. Individuals with CD4 > 500 cells/mm3 do not require prophylactic administration of azythromycin.  
|AnswerB=B
|AnswerB=B
|AnswerBExp=A CD4<300 cells/mL is associated with oral thrush and Kaposi's sarcoma but not disseminated MAC.
|AnswerBExp=HIV patients with CD4 between 200 and 500 cells/mm3 may develop oral candidiasis and Kaposi's sarcoma. Prophylactic administration of drugs is not recommended when CD4 counts are > 200 cells/mm3.
|AnswerC=C
|AnswerC=C
|AnswerCExp=A CD4<200 cells/mL is associated most importantly with Pneumocystis jirovecii pneumonia and requires Bactrim (TMP/SMX) prophylaxis not azithromycin.
|AnswerCExp=HIV patients with CD4 < 200 cells/mm3 may develop ''Pneumocystis jirovecii'' pneumonia, progressive multifocal leukoencephalopathy JC virus, or cryptosporidium-associated diarrhea. HIV patients with CD4 < 200 cells/mm3 require TMP-SMX prophylaxis against ''P. jirovecii'' pneumonia.
|AnswerD=D
|AnswerD=D
|AnswerDExp=A CD4<100 cells/mL is associated most importantly with cerebral toxoplasmosis as well as Pneumocystis jirovecii pneumonia both covered by Bactrim (TMP/SMX) prophylaxis.
|AnswerDExp=HIV patients with CD4 < 100 cells/mm3 may develop cerebral toxoplasmosis, disseminated histoplasmosis, or candida esophagitis. HIV patients with CD4 < 100 cells/mm3 require TMP-SMX prophylaxis against both ''P. jirovecii'' pneumonia and toxoplasmosis.
|AnswerE=E
|AnswerE=E
|AnswerEExp=Disseminated MAC is usually seen in patient with a CD4<50. Prophylaxis is recommended once counts drop below that threshold. Azithromycin once weekly (1200mg) is the preferred agent.
|AnswerEExp=HIV patients with CD4 < 50 cells/mm3 may develop cryptococcal meningitis, CMV retinitis, and disseminated mycobacterium avium complex (MAC). HIV patients with CD4 < 50 cells/mm3 require once-weekly azythromycin against MAC.
|EducationalObjectives=Disseminated MAC is usually seen in AIDS patients with a CD4<50 cell/mL. Azithromycin prophylaxis once weekly is recommended.
|EducationalObjectives=HIV patients with CD4 < 50 cells/mm3 may develop cryptococcal meningitis, CMV retinitis, and disseminated mycobacterium avium complex (MAC). HIV patients with CD4 < 50 cells/mm3 require once-weekly azythromycin against MAC.
|References=Jung AC, Paauw DS. Diagnosing HIV-related disease: using the CD4 count as a guide. J Gen Intern Med. 1998;13(2):131-6.
|References=Jung AC, Paauw DS. Diagnosing HIV-related disease: using the CD4 count as a guide. J Gen Intern Med. 1998;13(2):131-6.<br>
First Aid 2014 page 169, 188
|RightAnswer=E
|RightAnswer=E
|WBRKeyword=CD4 count, AIDS, Disseminated MAC
|WBRKeyword=CD4 count, AIDS, Disseminated MAC, Mycobaterium avium complex, Azythromycin, Prophylaxis, Prophylactic, MAC, HIV, AIDS, Opportunistic infections, Opportunistic infection
|Approved=No
|Approved=No
}}
}}

Revision as of 20:50, 17 October 2014
Author [[PageAuthor::Yazan Daaboul, M.D. (Reviewed by Yazan Daaboul, M.D.)]]
Exam Type ExamType::USMLE Step 1
Main Category MainCategory::Microbiology
Sub Category SubCategory::Infectious Disease
Prompt [[Prompt::A 44-year-old man with history of multiple unprotected sexual encounters was found to have a positive HIV ELISA during a local screening campaign. He was referred to an HIV clinic where he was advised to regularly monitor his CD4 counts. The patient admits that he has been non-compliant with his anti-retroviral therapy. A trend of his CD4 counts for the past 10 months are illustrated in the graph below. At which CD4 values should the physician first advise the prophylactic administration of azythromycin?

]]

Answer A AnswerA::A
Answer A Explanation [[AnswerAExp::CD4 > 500 cells/mm3 is considered normal. Individuals with CD4 > 500 cells/mm3 do not require prophylactic administration of azythromycin.]]
Answer B AnswerB::B
Answer B Explanation [[AnswerBExp::HIV patients with CD4 between 200 and 500 cells/mm3 may develop oral candidiasis and Kaposi's sarcoma. Prophylactic administration of drugs is not recommended when CD4 counts are > 200 cells/mm3.]]
Answer C AnswerC::C
Answer C Explanation [[AnswerCExp::HIV patients with CD4 < 200 cells/mm3 may develop Pneumocystis jirovecii pneumonia, progressive multifocal leukoencephalopathy JC virus, or cryptosporidium-associated diarrhea. HIV patients with CD4 < 200 cells/mm3 require TMP-SMX prophylaxis against P. jirovecii pneumonia.]]
Answer D AnswerD::D
Answer D Explanation [[AnswerDExp::HIV patients with CD4 < 100 cells/mm3 may develop cerebral toxoplasmosis, disseminated histoplasmosis, or candida esophagitis. HIV patients with CD4 < 100 cells/mm3 require TMP-SMX prophylaxis against both P. jirovecii pneumonia and toxoplasmosis.]]
Answer E AnswerE::E
Answer E Explanation [[AnswerEExp::HIV patients with CD4 < 50 cells/mm3 may develop cryptococcal meningitis, CMV retinitis, and disseminated mycobacterium avium complex (MAC). HIV patients with CD4 < 50 cells/mm3 require once-weekly azythromycin against MAC.]]
Right Answer RightAnswer::E
Explanation [[Explanation::Azithromycin is a macrolide antibiotic that binds to 23S rRNA of the 50S ribosomal subunit and inhibits protein synthesis via inhibition of translocation. Azythromycin may be administered to treat cases of atypical pneumonias and gram-positive cocci infections in patients allergic to penicillin. In addition, azythromycin may be administered prophylactically to HIV-positive patients whose CD4 counts are below 50 cells/mm3 to prevent the development of disseminated Mycovacterium Avium Complex (MAC). Mycobacterium avium complex (MAC) includes the following organisms: M. avium and M. intracellulare.

The table below summarizes the AIDS associated illnesses and the corresponding CD4 counts at which they are observed. The following table summarizes the association between opportunistic infections and CD4 counts in HIV patients.
Educational Objective: HIV patients with CD4 < 50 cells/mm3 may develop cryptococcal meningitis, CMV retinitis, and disseminated mycobacterium avium complex (MAC). HIV patients with CD4 < 50 cells/mm3 require once-weekly azythromycin against MAC.
References: Jung AC, Paauw DS. Diagnosing HIV-related disease: using the CD4 count as a guide. J Gen Intern Med. 1998;13(2):131-6.
First Aid 2014 page 169, 188]]

Approved Approved::No
Keyword WBRKeyword::CD4 count, WBRKeyword::AIDS, WBRKeyword::Disseminated MAC, WBRKeyword::Mycobaterium avium complex, WBRKeyword::Azythromycin, WBRKeyword::Prophylaxis, WBRKeyword::Prophylactic, WBRKeyword::MAC, WBRKeyword::HIV, WBRKeyword::AIDS, WBRKeyword::Opportunistic infections, WBRKeyword::Opportunistic infection
Linked Question Linked::
Order in Linked Questions LinkedOrder::
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