Many possible Peyronie’s causes, few proven ideas

While the cause of Peyronie's disease is not well understood, it is generally thought to be the result of an excessive response to wound healing, or exaggerated internal scar formation at the site of injury.  The traumatic cause of Peyronie’s disease is said to be repeated minor trauma to the penis that occurs during sexual activity; from my experience it is often from significant or major injury during sexual activity in which the penis is suddenly bent during sexual intercourse or during aggressive foreplay of various types.   This type of injury can also occur during a work related or sports accident.

Factors that influence causes of Peyronie's Disease

• Inherited weakness – a genetic predisposition is thought to exist because Peyronie's disease is seen to be more common in men with family members who also have  PD, or Dupuytren’s contracture, or Ledderhose disease, or systemic lupus erythematosus, (SLE, a connective tissue disorder).   This is supported by a commonly found inherited abnormality of the human leukocyte antigen B27 (HLA-B27).
• Injury – Peyronie's disease can sometimes start after trauma to the penis in which localized bleeding occurs.   Sufficient injury may happen during  an accident related to sexual intercourse, a medical procedure such as catheterization in which a tube or catheter is passed through the urethra of the penis, or unusual events like falling forward on the ice or even prolonged bicycle riding.
• Vitamin E deficiency – some evidence this makes Peyronie's disease easier to occur after injury.
• Drug side-effects – Peyronie’s disease is a rare side effect of blood pressure medications that belong to a group called beta blockers (Inderal).
• Diabetes – Prolonged diabetes can predispose to damage to the internal lining of blood vessels, including the penis, making either trauma, vitamin E deficiency or genetic factors easier to trigger an occurrence of Peyronie's disease.
• Infection – When inflammation occurs secondary to an infection it sometimes can spread to the blood vessel walls (vasculitis) causing a reduced blood flow because the response is very similar to a direct trauma to the penis.

Peyronie’s disease and wound healing
Two things you need to know about Peyronie’s penis anatomy is that the penis is made of three long tube-shaped cylinders of tissue – two larger ones called the corpus cavernosae, and one smaller one called the corpus spongiosum; both are filled with a blood-filled type of tissue that resembles a sponge. And the other is that these three tissue structures are wrapped by a layer of tough but delicate tissue called the tunica albuginea.   During sexual arousal or when erection occurs nerve impulses from the higher centers are sent down to chambers signal that they should fill with blood, resulting in the penis being able to expand, straighten and stiffen, causing trouble with sexual activity.

The two corpus cavernosae are surrounded by a sheath of thin elastic tissue called the tunica albuginea, which very slightly stretches during an erection.  During penile injury the tunica can become damaged, causing inflammation.

When Peyronie's disease develops – especially easily in men who are genetically predisposed, but in other men as well when the injury is more significant – normal wound-healing process does not occur because the internal scar tissue becomes excessive.  When this happens the area of the tunica albuginea with the internal scar is no longer flexible and expandable, and the ability to develop an erection in Peyronie’s disease is reduced totally or partially.   When erect, the Peyronie’s penis is distorted and often painful.

For more information, cause of Peyronie’s disease.