Parker Posey, 40, has dropped out of the new off-Broadway show This at Mainstage Theater after being diagnosed with Lyme disease. The show will go on as planned, with previews beginning on November 6 and opening night on December 2, though a replacement for Posey has not yet been announced. Lyme disease, a tick-borne disease, is usually picked up in grassy or forested areas, and can lead to severe and chronic symptoms if untreated.