WBR1502

Author	PageAuthor::William J Gibson
Exam Type	ExamType::USMLE Step 2 CK
Main Category	MainCategory::Internal medicine
Sub Category	SubCategory::Neurology
Prompt	[[Prompt::A 43 year old man presents with three weeks of severe dysphagia to solids resulting in a 25 pound weight loss. He has oral candidiasis and is admitted for inpatient workup. EGD reveals esophageal stricture. The patient reports that since the onset of his dysphagia, he has stopped taking his anti-retroviral regimen due to difficulty swallowing. On day 4 of his admission, he reports headaches and his mental status begins deteriorating. An MRI with contrast is performed (shown below). What is the most appropriate therapy to address the cause of this patient's neurological symptoms?]]
Answer A	AnswerA::Methotrexate
Answer A Explanation	AnswerAExp::Methotrexate is the preferred first line therapy for primary CNS lymphoma. The presence of multiple enhancing lesions in this patient's MRI make the diagnosis of primary CNS lymphoma less likely than Toxoplasmosis.
Answer B	AnswerB::Dexamethasone
Answer B Explanation	[[AnswerBExp::Dexamethasone is a corticosteroid used to decrease inflammation that may be associated with increased inctracranial pressure. While this patient may have some increased intracranial pressure from his toxoplasma infection, dexamethasone would not be the definitive therapy.]]
Answer C	AnswerC::Trimethoprim-Sulfamethoxazole
Answer C Explanation	AnswerCExp::Trimethoprim-Sulfamethoxazole (TMP-SMX) is often used as a second agent in regimens against Toxoplasmosis. TMP-SMX is synergistic in combination with Pyrimethamine. However, TMP-SMX is not recommended as a monotherapy against Toxoplasmosis.
Answer D	AnswerD::Pyrimethamine
Answer D Explanation	AnswerDExp::Pyrimethamine is the drug of choice in treating Toxoplasmosis.
Answer E	AnswerE::Azithromycin
Answer E Explanation	AnswerEExp::Azithromycin is not considered an active agent against Toxoplasmosis. There are some reports of its efficacy against toxoplasma, but the literature on it is scant and conflicting.
Right Answer	RightAnswer::D
Explanation	[[Explanation::The patient in this vignette has cerebral toxoplasmosis. The differential for CNS lesions in HIV patients should include: toxoplasmosis, progressive multifocal leukoencephalopathy, and primary CNS lymphoma. The MRI in this patient shows multiple, contrast enhancing lesions. The most anterior of these lesions produces a small midline shift from mass effect. Typically primary CNS lymphoma would present with a solitary intracranial mass (the primary tumor), making this diagnosis unlikely. The presence of a mass effect in this scan makes progressive multifocal leukoencephalopathy, a demyelinating disease caused by JC virus, a less likely diagnosis. The imaging and symptoms in this patient are most consistent with cerebral toxoplasmosis. Given the diagnosis of cerebral toxoplasmosis, the best definitive treatment is pyrimethamine, an antibiotic that inhibits dihydrofolate reductase, the bacterial enzyme responsible for folic acid synthesis. Because of its mechanism of action, patients are also treated with folic acid to protect against myelosuppression. Pytimethamine has been a controversial drug in the media lately, as its manufacturer (Turing Pharmaceuticals) raised its price by 5000%. In reality, the approach to HIV patients with CNS lesions is complicated by the fact that they can sometimes have more than one active process occuring. In one study of HIV patients undergoing brain biopsy, 6% had histologic evidence for more than one diagnosis. Educational Objective: Multiple ring enhancing lesions in the brain of an HIV infected patient is highly concerning for cerebral Toxoplasmosis. Pyrimethamine is the preferred therapy. References: Blueprints Neurology 3E page 91. Gildenberg PL, Gathe JC, Kim JH. Stereotactic biopsy of cerebral lesions in AIDS. Clin Infect Dis. 2000;30(3):491-9.]]
Approved	Approved::No
Keyword	WBRKeyword::MGHRDA, WBRKeyword::Neurology, WBRKeyword::HIV, WBRKeyword::Toxoplasma, WBRKeyword::Toxoplasmosis, WBRKeyword::Antibiotics, WBRKeyword::Infection, WBRKeyword::Intracranial mass
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