Peyronie's disease is a medical condition characterized by the development of a lump on the shaft of the penis. This lump is a scar (plaque) that forms on the lining (tunica) of the erectile body (corpus cavernosum) and is believed to be the result of injury to the penis during sexual relations. Early on following the trauma, an inflammatory reaction occurs, often bringing a man's attention to the problem because of pain associated with erection. With time, the inflammation progresses and a scar develops. The time to develop this scar and the degree to which it occurs varies from patient to patient. Often the process heals itself over the first 12 months after the scar forms. In some cases, however, the scar formation is severe. In these cases, the scar becomes progressively harder and more obvious, causing the penis to curve during erection. While the scar is benign (non-cancerous), the resulting curvature may lead to the inability to have sexual intercourse.