Wound healing leads to formation of granulation tissue, which includes blood vessels, fibroblasts and collagen. Over time the granulation tissue transforms into a well healed scar. In a scar we see mostly collagen and only few blood vessels, fibroblast left. The first collagen laid down by fibroblasts is T-III collagen, over time it changes into type I, which is strongest type of collagen. So scars consist of mostly collagen.
Keloid and hypertrophic scars, when wound healing gone stray:
Hypertrophic scars are characterized by an accumulation of myofibroblasts expressing smooth muscle actin and thin, randomly organized, collagen fibres, both usually arranged in nodules. In keloids myofibroblasts, expressing smooth muscle actin, are usually absent, the cellularity is less marked and the collagen bundles are thicker than in hypertrophic scars.
Hypertrophic scars are very protubering and raised, excessive production of granulation tissue, genetic factors are involved. Hypertrophic scars are raised, firm, erythematous scars formed as the result of overzealous collagen synthesis coupled with limited collagen lysis during the remodeling phase of wound healing. The result is the formation of thick, hyalinized collagen bundles consisting of fibroblasts and fibrocytes. Despite the obvious tissue proliferation, they tend to stay in their own boundaries and are limited to the borders of the initial injury..
A Keloid scar has genetic predisposition, more common in african-american population. Keloids tend to occur in earlobe, along the neck, the face and sometimes forearms as well. They can often produce this large masses of collagen. if you do a biopsy through this mass, you would see it's a scar, it's mostly pink collagen, large bundles of T-3 collagen. In a keloid scar wound healing has gone stray. Why? Because in normal wound healing it starts with collagen T-III and overtime it should mature to type I. In a keloid wound healing starts with T-III collagen and for many years it remains collagen III. Unlike a hypertrophic scar, keloids extend beyond wound margins and do not regress over time. They are also firmer than a hypertrophic scar. Keloids present as smooth, firm, irregularly shaped lesions. Keloids exhibit a prolonged, proliferative phase resulting in the appearance of thick hyalinized collagen bundles similar to those produced by hypertrophic scars, but extend beyond the margins of the inciting wound and do not regress over time. Although they can be seen in all skin types, keloids tend to appear most frequently in patients with darker skin tones and are related to an inherited metabolic alteration in collagen. Removal of hypertrophic scars and keloids is feasible using co2 and YAG laser. Indeed they are the best scar candidate for laser scar removal
Atrophic facial scars are dermal depressions most commonly caused by collagen destruction during the course of an inflammatory skin disease such as cystic acne or varicella. Scarring after inflammatory or cystic acne can manifest as atrophic, saucerized, ice pick, or boxcar scars. Treatment of scars of this type invloves certain considerations. While ice pick and boxcar scars respond best to dermal filler augmentation or punch excision, these types of scarring, atrophic scars, usually respond well to laser resurfacing.
Macules or "pseudo- scar" , see below, hyperpigmented skin and its treatment
Post-inflammatory pigmentation, see below, hyperpigmented skin and its treatment
Striae distensae
Striae, or stretch marks, are linear bands of atrophic or wrinkled skin. These horizontal bands appear whiter than the surrounding skin. Formation of stretch marks may be the result of rapid weight loss or weight gain in areas that are excessively stretched. So they are more commonly seen in breasts, abdomen, thighs and joint areas. Dermal inflammation and dilated capillaries mark the initial presentation, which results in an erythematous appearance with characteristic pink, lavender, and purple hues. Later, stretch marks appear hypopigmented and fibrotic. Pathogenesis remains unclear, although estrogen and mast cell degranulation with elastolysis may be contributing factors. The dermis seems to be looser and more floccular. They also show an increase in glycosaminogylcan content.
Removal techniques
Initiating treatment before the scarring process is complete is the best mode for treatment of striae. Considering the fact that more than 90% of pregnant women develop stretch marks, it would be wise to consider a preventive treatment before the pregnancy ends. Combination of 20% glycolic acid and 10% ascorbic acid seems to be as promising as application of 0.05 Retinoic acid and glycolic acid regimen. The result could persist one year after discontinuation of therapy. Laser is another modality to treat stretch marks. Treatment with pulsed dye laser shows significant improvement. This is associated with increase in dermal elastin and could be attributed to the observed improvement.
Deviations in wound healing, Keloid versus hypertrophic scar
