Normal Tunica Albuginea Function
A dual-layer collagen sheath lets the penis lengthen straight under pressure.
- 2 mm: Tunica thickness (bilayer collagen sheath)
- ~100 mmHg: Erect pressure (intracavernosal peak)
- 98%: Elastic recoil (baseline tissue compliance)
- ~1 in 11: Prevalence Peyronie's (men over 40)
Two-layer collagen architecture
Outer longitudinal fibers, inner circular fibers, both elastic.
Erectile filling mechanics
Corpora cavernosa fill, sheath stretches evenly, shaft stays straight.
Why symmetry matters
Even wall tension on both sides keeps curvature near zero.
Microtrauma & Inflammatory Phase
Repetitive bending microtears the tunica, triggering localized healing.
- Buckling injury: Onset trigger (often unnoticed at the time)
- 6–18 mo: Acute phase length (active inflammatory window)
- TGF-β1: Cytokine driver (key fibrotic signal)
- ~35%: Pain during phase (of patients report it)
Microvascular injury
Small tears in the septum trigger a local clotting and healing cascade.
Inflammatory infiltrate
Fibroblasts and immune cells accumulate at the injury site.
Aberrant healing
TGF-β1 overdrives collagen deposition instead of normal repair.
Fibrous Plaque Formation
Disorganized collagen hardens into a stiff, inelastic plaque patch.
- Dorsal >> ventral: Plaque location (typical distribution)
- I & III excess: Collagen type shift (disorganized bundles)
- ~30%: Calcification rate (of chronic plaques)
- >12 months: Chronic phase onset (stable, non-tender plaque)
Collagen disorganization
Randomly cross-linked fibers replace the ordered elastic weave.
Localized stiffening
The plaque patch stops stretching while surrounding tissue still does.
Calcified nodules
Long-standing plaques can harden further with calcium deposits.
Curvature Develops
A one-sided stiff patch forces the erect shaft to bow toward it.
- 15°–90°: Curvature range (mild to severe cases)
- >30°: Surgery threshold (often considered for repair)
- ~50%: Erectile dysfunction (co-occurring in patients)
- ~65%: Shortening reported (of Peyronie's patients)
Asymmetric expansion
The plaque side resists stretch, the healthy side elongates freely.
Angle measurement
Curvature is graded during a pharmacologically induced erection.
Functional impact
Severe bends can make penetration painful or impossible.
Collagenase Injection Treatment
Clostridium histolyticum enzyme injections break down plaque collagen.
- CCH: Drug name (collagenase clostridium histolyticum)
- Up to 4 cycles: Typical course (2 injections per cycle)
- ~34%: Curvature reduction (average trial improvement)
- 2013: FDA approval (brand name Xiaflex)
Enzymatic collagen cleavage
Collagenase enzymes target and digest the excess plaque collagen.
Modeling & stretching
Manual penile modeling after injection helps realign remaining fibers.
Weeks-to-outcome timeline
Improvement builds gradually over the injection weeks that follow.