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Rheumatoid arthritis — USMLE Step 2 CK MCQ

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HardInternal MedicineRheumatoid arthritisUSMLE Step 2 CK

A 42-year-old man with advanced HIV has painful perianal ulcerations that persist after 14 days of correctly dosed intravenous acyclovir. Viral culture grows herpes simplex virus type 2 and phenotypic susceptibility testing confirms acyclovir resistance. Creatinine and electrolytes are normal, and there is no bacterial superinfection. Which antiviral treatment is most appropriate?

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Correct answer: D — Begin intravenous foscarnet with renal and electrolyte monitoring

The best answer is “Begin intravenous foscarnet with renal and electrolyte monitoring”. Acyclovir-resistant HSV generally has altered or absent viral thymidine kinase, producing cross-resistance to valacyclovir and usually famciclovir. Intravenous foscarnet directly inhibits viral DNA polymerase without requiring thymidine-kinase activation and is the CDC treatment of choice. Nephrotoxicity and electrolyte disturbances require close monitoring and infectious-disease consultation.

Reference: CDC STI Treatment Guidelines: Antiviral-Resistant HSV: https://www.cdc.gov/std/treatment-guidelines/herpes.htm