Syphilis is a sexually transmitted disease caused by the spirochete Treponema pallidum. A chancre usually develops initially. Organ involvement and neurological complications may occur, sometimes several years after the initial exposure. We managed two patients with syphilis responsible for joint or neurological manifestations, diagnosed in 2008. One patient presented with oligoarthritis involving the knees and right elbow, coinciding with a maculopapular and pustular eruption. In the other patient, meningoradiculitis involving the T8, T9, and T10 metameres prompted a test for Lyme disease, which was weakly positive, leading to evaluation for false-positivity due to a cross-reaction. Neither patient was infected with the HIV.