A 34-year-old woman with HIV and a CD4 count of 516 cells/mm³ comes to clinic for routine follow-up. She was diagnosed with secondary syphilis 6 months ago, at which time she had a rapid plasma reagin (RPR) titer of 1:256 and received appropriate treatment for syphilis. At this time, the RPR titer has declined to 1:16. She reports one new sex partner since her last visit but denies any genital lesions, rash, fever, lymphadenopathy, ocular symptoms, headache, hearing difficulties, or other symptoms. A complete examination, including a neurologic examination, is unremarkable.