Peyronie's disease occurs when a man's erection bends in one direction.
Men have balloon-like blood vessels in their penis that fill with blood when they have erections.
Sometimes scar tissue forms in the balloons. Scars cannot expand as much as balloons do, so the erected penis bends toward the scar side. Men with Peyronie's disease are usually told to live with it unless the erection becomes painful or the bend is so great that the man cannot engage in sexual relations. Then the usual treatment is to cut out the scar and replace it with a graft. Needless to say, this procedure doesn't always work.