The cause of Peyronie's disease is not well understood. Nonetheless, research findings that shed light on this question are of interest to patients as well as to medical scientists.

Consider a more specific question: What causes the erect penis to bend? The answer lies in the functioning of the erection mechanism, the corpora cavernosa. These cigar shaped, paired balloon-like chambers must inflate with blood to create an erection. Their connective tissue wall, or tunica albuginea, produces rigidity only when maximally stretched. It is elastic to a point, but unlike the flimsy wall of a balloon, tunica albuginea is interlaced with strong connective tissue fibers. These fibers control expansion, determine the shape of the erect penis, and translate internal filling into structural rigidity.

Peyronie's disease is a disorder of the tunica albuginea. By producing firm areas, or plaques, it focally interferes with the expansion of this normally pliant material. Plaques can be either regions of reversible inflammation in early phases of the disease, or permanent scars later on. Regardless of their composition, they alter the shape of the distended corpora cavernosa and distort the resulting erection. Like a piece of cellophane tape on the wall of a balloon, they cause uneven inflation and bending out of column.

The real question is, what produces these plaques? Early on as painfully swollen patches of inflammed tunica albuginea, or later in the disease as the site of inelastic and permanently disfiguring scars, they are at the heart of the problem.

Microscopic and chemical studies have shown that plaques represent stages in the wound healing process, whether early or late. Whatever brings on Peyronie's disease appears to do so by inappropriately turning on this normally healthful process.

More accurately, wound healing may not be inappropriate in all cases. We know that one cause of Peyronie's disease is overt trauma to the erect penis. This can range from painful unexpected angulation during sex, to actual rupture of the corpora cavernosa, an even that produces immediate loss of the erection and subsequent severe swelling. The fact is, most men with Peyronie's relate no such occurences.

Probably, all sexually active men experience some degree of wear and tear on particular vulnerable areas of the erection mechanism. Both the structural arrangement of the corpora and the inherent elasticity of its connective tissues counteract the strong mechanical stresses imposed by active intercouse. But by the time men reach their mid fifties, inherent connective tissue elasticity is on the wane. The median age for the appearance of Peyronie's disease is fifty-five.

Peyronie's plaques most commonly appear along the top of the penis. It is this region between the paired corpora, along the upper edge of the "inflatable I-beam"created by their inflation, that is vulnerable to stress-induced delamination . This is the region where fibrin, a protien involved in activating wound healing, can be found in men with Peyronie's disease.

Autopsy studies on men have shown that the earliest microscopic changes thought to be evidence of Peyronie's disease are acutally a common finding. Though many men develop these changes, they evolve into Peyronie's plaques in a very small percentage of cases. So what causes normal wear and tear to abnormally activate wound healing? At this point there is no clear answer. Peyronie's disease is more common in diabetics and in men with gout, two condtions that can affect connective tissue healing. It is also more common in the presence of Dupuytren's contractures. These scars of the fascial covering of the finger tendons in the palm of the hand can be inherited, and may reflect an abnormal tendency toward scar formation in other areas.