[libribook.com] Traumatic Scar Tissue Management 1st Edition

Keloids are typically pink to purple in color and may be accompanied by
hyperpigmentation. The borders of the keloid are well demarcated but irregular
in outline. A hypertrophic scar has a similar appearance but is usually linear, if
following a surgical scar, or papular or nodular if following inflammatory and
ulcerating lesions. Both lesions are commonly pruritic, but keloids may be the
source of significant pain and hyperesthesia (excessive physical sensitivity,
especially of the skin) (Gauglitz et al. 2011).
In most cases, hypertrophic scarring develops in wounds at anatomic locations
with high tension (joints), such as shoulders, neck, knees and ankles, whereas
anterior chest, shoulders, earlobes, upper arms and cheeks have a higher
predilection for keloid formation. Eyelids, cornea, palms, mucous membranes,
genitalia and soles are generally less affected. Keloids tend to recur following
excision, whereas new hypertrophic scar formation is rare after excision of the
original hypertrophic scar (Gauglitz et al. 2011).
Histologically, both hypertrophic and keloid scars contain an overabundance of
dermal collagen. Hypertrophic scars comprise primarily Type III collagen that lie
parallel to the epidermal surface with abundant nodules containing
myofibroblasts (MFBs), large extracellular collagen filaments and plentiful
(acidic) mucopolysaccharides (Slemp & Kirschner 2006). Keloid tissue, in
comparison, primarily comprises disorganized Type I and III collagen,
containing hypocellular collagen bundles with no nodules or excess MFBs
(Slemp & Kirschner 2006).
Both scar types overproduce multiple fibroblast proteins, including fibronectin,
suggesting either pathological determination of wound healing signals or a
failure of the appropriate regulation of wound-healing cells (Gauglitz et al. 2011,
Chapelle & Bove 2013).