Peyronie's disease is the formation of a hard lump on the penis, which forces the penis to bend during an erection. This bending may cause pain and make sexual intercourse difficult or impossible.

The lump that hardens and bends the penis is composed of fibrous tissues that grow in the penile lining. Experts don't know what causes this growth of fibrous tissue.

Peyronie's disease is an uncommon condition, affecting men age 40 and older. It sometimes improves on its own. If the condition does not improve or it gets worse, treatment to relieve pain and severe bending of the penis includes medicine, radiation therapy, or surgery.