WBR0434: Difference between revisions

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{{WBRQuestion
{{WBRQuestion
|QuestionAuthor={{Rim}}
|QuestionAuthor={{Rim}}, {{AJL}} {{Alison}}
|ExamType=USMLE Step 1
|ExamType=USMLE Step 1
|MainCategory=Microbiology
|MainCategory=Microbiology
Line 20: Line 20:
|MainCategory=Microbiology
|MainCategory=Microbiology
|SubCategory=Neurology
|SubCategory=Neurology
|Prompt=A 28 year old HIV-positive female patient presents to the emergency department with high grade fever, headache, and new onset tonic-clonic seizures.  The patient also explains she has been anorexic and very weak recently.  Laboratory work-up reveals CD4 count = 80 cells/µL per year.  Head computer tomography (CT) scan shows multiple ring enhancing lesions in the frontal lobes.  The patient requires treatment with a medication that has which of the following mechanisms of action?
|Prompt=A 28-year-old HIV-positive female presents to the emergency room with a high grade fever, headache, weakness, and tonic-clonic seizures.  The patient has a recent history of anorexia.  Laboratory work-up reveals CD4 count = 80 cells/µL per year.  Head computer tomography (CT) scan demostrates multiple ring enhancing lesions in the frontal lobes.  The patient requires treatment with a medication that uses which of the following mechanisms of action?
|Explanation=[[Cerebral toxoplasmosis]] is caused by [[Toxoplasma gondii]], an opportunistic parasitic infection that often infects HIV-positive patients with CD4 counts < 100 cells/µL per year.  [[Toxoplasmosis]] causes a clinical syndrome of fever, headache, and new-onset seizures typically in an HIV-positive patient.  Multiple [[ring-enhancing lesions]] on head CT scan are characteristic.  Treatment of cerebral toxoplasmosis includes [[pyrimethamine]], a [[dihydrofolate reductase inhibitor]], and [[sulfadiazine]], a [[sulfa drug]] that is a dihydropteroate synthetase inhibitor.
|Explanation=[[Cerebral toxoplasmosis]], caused by ''[[Toxoplasma gondii]]'', is an opportunistic parasitic infection that frequently infects HIV-positive patients with CD4 counts < 100 cells/µL per year.  [[Toxoplasmosis]] manifest with fever, headache, and new-onset seizures.  Multiple [[ring-enhancing lesions]] upon cranial CT scan are characteristic.  Treatment of [[cerebral toxoplasmosis]] includes [[pyrimethamine]], a [[dihydrofolate reductase inhibitor]], and [[sulfadiazine]], a [[sulfa drug]] that is a [[dihydropteroate synthetase]] inhibitor.


Educational Objective:
|EducationalObjectives=
Cerebral toxoplasmosis causes a clinical syndrome of fever, headache, and new-onset seizures typically in an HIV-positive patient with CD4 count < 100 cells/µL per year.  Treatment of cerebral toxoplasmosis includes pyrimethamine, a dihydrofolate reductase inhibitor, and sulfadiazine, a sulfa drug that is a dihydropteroate synthetase inhibitor.
Cerebral toxoplasmosis, frequently occurring in HIV-positive individuals  with CD4 count < 100 cells/µL per year, often manifests with a fever, headache, and new-onset seizures.   
Treatment of [[cerebral toxoplasmosis]] includes [[pyrimethamine]], a [[dihydrofolate reductase inhibitor]], and [[sulfadiazine]], a [[sulfa drug]] that is a [[dihydropteroate synthetase]] inhibitor.
|AnswerA=Inhibition of heme polymerase activity
|AnswerA=Inhibition of heme polymerase activity
|AnswerAExp=[[Chloroquine]], an antimalarial drug, is a plasmodium heme polymerase inhibitor.
|AnswerAExp=[[Chloroquine]], an antimalarial drug, is a plasmodium heme polymerase inhibitor.
|AnswerB=Inhibition of dihydrofolate reductase activity
|AnswerB=Inhibition of dihydrofolate reductase activity
|AnswerBExp=[[Pyrimethamine]], a drug used to treat [[toxoplasmosis]], is a dihydrofolate reductase inhibitor.
|AnswerBExp=[[Pyrimethamine]], a drug frequently used to treat [[toxoplasmosis]], is a dihydrofolate reductase inhibitor.
|AnswerC=Free radical toxicity of organism’s DNA
|AnswerC=Free radical toxicity of organism’s DNA
|AnswerCExp=[[Metronidazole]], an [[antibiotic]] and antiprotozoal, forms free radical metabolites that are toxic to bacterial DNA.
|AnswerCExp=[[Metronidazole]], an [[antibiotic]] and antiprotozoal, forms free radical metabolites that are toxic to bacterial DNA.
|AnswerD=Blockade of peptide bond formation at 50S ribosomal subunit
|AnswerD=Blockade of peptide bond formation at 50S ribosomal subunit
|AnswerDExp=Several [[antibiotics]], including [[chloramphenicol]], [[macrolides]], [[clindamycin]], [[streptogramins]], and [[linezolid]], block peptide bond formation at 50S ribosomal subunit.
|AnswerDExp=Several [[antibiotics]], including [[chloramphenicol]], [[macrolides]], [[clindamycin]], [[streptogramins]], and [[linezolid]], block peptide bond formation at the 50S ribosomal subunit.
|AnswerE=Inhibition of DNA polymerase activity
|AnswerE=Inhibition of DNA polymerase activity
|AnswerEExp=Antiviral medications, such as [[acyclovir]], [[ganciclovir]], [[foscarnet]], and [[cidofovir]] are DNA polymerase inhibitors.
|AnswerEExp=Antiviral medications, such as [[acyclovir]], [[ganciclovir]], [[foscarnet]], and [[cidofovir]] are DNA polymerase inhibitors.
|RightAnswer=B
|RightAnswer=B
|WBRKeyword=Toxoplasma gondii, toxomplasmosis, HIV, seizure, ring enhancing lesion, pyrimethamine, dihydrofolate reductase inhibitor
|WBRKeyword=Toxoplasma gondii, toxomplasmosis, HIV, seizure, ring enhancing lesion, pyrimethamine, dihydrofolate reductase inhibitor
|Approved=No
|Approved=Yes
}}
}}

Revision as of 14:44, 22 July 2014
Author [[PageAuthor::Rim Halaby, M.D. [1], Alison Leibowitz [2] (Reviewed by Alison Leibowitz)]]
Exam Type ExamType::USMLE Step 1
Main Category MainCategory::Microbiology
Sub Category SubCategory::Neurology
Prompt [[Prompt::A 28-year-old HIV-positive female presents to the emergency room with a high grade fever, headache, weakness, and tonic-clonic seizures. The patient has a recent history of anorexia. Laboratory work-up reveals CD4 count = 80 cells/µL per year. Head computer tomography (CT) scan demostrates multiple ring enhancing lesions in the frontal lobes. The patient requires treatment with a medication that uses which of the following mechanisms of action?]]
Answer A AnswerA::Inhibition of heme polymerase activity
Answer A Explanation [[AnswerAExp::Chloroquine, an antimalarial drug, is a plasmodium heme polymerase inhibitor.]]
Answer B AnswerB::Inhibition of dihydrofolate reductase activity
Answer B Explanation [[AnswerBExp::Pyrimethamine, a drug frequently used to treat toxoplasmosis, is a dihydrofolate reductase inhibitor.]]
Answer C AnswerC::Free radical toxicity of organism’s DNA
Answer C Explanation [[AnswerCExp::Metronidazole, an antibiotic and antiprotozoal, forms free radical metabolites that are toxic to bacterial DNA.]]
Answer D AnswerD::Blockade of peptide bond formation at 50S ribosomal subunit
Answer D Explanation [[AnswerDExp::Several antibiotics, including chloramphenicol, macrolides, clindamycin, streptogramins, and linezolid, block peptide bond formation at the 50S ribosomal subunit.]]
Answer E AnswerE::Inhibition of DNA polymerase activity
Answer E Explanation [[AnswerEExp::Antiviral medications, such as acyclovir, ganciclovir, foscarnet, and cidofovir are DNA polymerase inhibitors.]]
Right Answer RightAnswer::B
Explanation [[Explanation::Cerebral toxoplasmosis, caused by Toxoplasma gondii, is an opportunistic parasitic infection that frequently infects HIV-positive patients with CD4 counts < 100 cells/µL per year. Toxoplasmosis manifest with fever, headache, and new-onset seizures. Multiple ring-enhancing lesions upon cranial CT scan are characteristic. Treatment of cerebral toxoplasmosis includes pyrimethamine, a dihydrofolate reductase inhibitor, and sulfadiazine, a sulfa drug that is a dihydropteroate synthetase inhibitor.

Educational Objective: Cerebral toxoplasmosis, frequently occurring in HIV-positive individuals with CD4 count < 100 cells/µL per year, often manifests with a fever, headache, and new-onset seizures. Treatment of cerebral toxoplasmosis includes pyrimethamine, a dihydrofolate reductase inhibitor, and sulfadiazine, a sulfa drug that is a dihydropteroate synthetase inhibitor.
References: ]]

Approved Approved::Yes
Keyword WBRKeyword::Toxoplasma gondii, WBRKeyword::toxomplasmosis, WBRKeyword::HIV, WBRKeyword::seizure, WBRKeyword::ring enhancing lesion, WBRKeyword::pyrimethamine, WBRKeyword::dihydrofolate reductase inhibitor
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