Excessive collagen formation during the remodeling phase of wound healing can result in a keloid or hypertrophic scar.

Keloids and hypertrophic scars consist of connective tissue rich in fibroblasts, myofibroblasts, and bundles of collagen fibers that are arranged in a disorganized fashion in keloids and in parallel in hypertrophic scars.

PDGF and transforming growth factor-beta (TGF-beta) plays a major role during proliferative phase

If persistently elevated -> hypertrophic or disfiguring scars

In addition, the fibroblasts in hypertrophic scars often have altered TGF-beta signaling due to increased TGF-beta receptor expression.