Peyronie's disease is characterized by the formation of hardened tissue (fibrosis) in the penis that causes pain, curvature, and distortion, usually during erection. The penis is the male organ for reproduction and urination. It is composed of two columns of erectile tissue (the corpora cavernosa); the corpus spongiosum, which contains the tube that carries urine and semen from the body (urethra); and the sheath that surrounds the erectile tissue (tunica albuginea). In Peyronie's disease, dense, fibrous scar tissue (plaque) forms in the tunica albuginea.
According to a report published in 1995 by the National Institutes of Health, Peyronie's disease occurs in about 1% of men. It is most common between the ages of 45 and 60, but it also occurs in young and elderly men. Prevalence may be higher because of reluctance to seek medical attention for the condition and failure to report in cases with mild symptoms.