DNA structure, replication, and polymerases
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A 45-year-old man with HIV infection develops progressive difficulty climbing stairs and lifting objects over four months. He has received combination antiretroviral therapy for several years, and his plasma HIV RNA remains undetectable. Muscle biopsy shows numerous ragged-red fibers, and analysis of the specimen shows marked depletion of mitochondrial DNA. His strength improves over the following months after one component of his antiretroviral regimen is replaced.