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HIV Clinical Care Question Bank

Evaluation and Management of Virologic FailureQuestion 4/10

A 64-year-old man has an extensive past history of taking antiretroviral medications, including 2 years of zidovudine monotherapy, 1 year of zidovudine-lamivudine, and 3 years of stavudine, lamivudine, and indinavir. For the past 4 years, he has maintained virologic suppression on a regimen of darunavir-cobicistat, fostemsavir, and maraviroc. The clinical notes in his chart repeatedly state that his genotype shows thymidine analog mutations (TAMs).

Which one of the following best defines the group of mutations known as thymidine analog mutations (TAMs)?

Figure 1. Thymidine Analog Mutations (TAMs)
Illustration by David H. Spach, MD
The NRTI drugs inhibit HIV replication by blocking the extension of the elongating primer chain in a process referred to as chain termination. Resistance associated with TAM mutations occurs as a result of primer unblocking (enhanced pyrophosphorolytic removal of the chain terminating drug).
Figure 2. Mechanism of Resistance Mechanisms Associated with TAM Mutations
The NRTI drugs inhibit HIV replication by blocking the extension of the elongating primer chain in a process referred to as chain termination. Resistance associated with TAM mutations occurs as a result of primer unblocking (enhanced pyrophosphorolytic removal of the chain terminating drug).
Source: Illustration by David H. Spach, MD
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Question Last Updated
January 28th, 2025

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