LSS The Skin
Alexandra Burke-Smith
Diabetes In diabetes, glucose molecules are attached to all types of protein – a process called non-enzymatic glycosylation This makes proteins less active, including proteins important for the defence against bacterial infection Healing thus takes much longer in diabetics, and the risk of infection is high Keloids
These are dermal fibrotic lesions that a variation of the normal wound healing process They usually occur during healing of a deep skin wound, because of excessive production of ECM proteins, collagen, elastin + proteoglycans – i.e. the result of a prolonged inflammatory response in the wound Formation can occur within a year after injury, and enlarge well beyond the original scar margin The most frequently involved sites are areas subjected to high skin tension e.g. anterior chest, should, anterior neck (+ any wounds that cross skin tension lines)
Hypertrophic scars These are raised, erythematous, fibrotic lesions that usually remain confined within the borders of the original wound. They occur within months of the initial trauma and have a tendency to remain stable or regress with time Risk factors/Causes The most important risk factor for the development of abnormal scars is a wound healing by secondary intention, especially if the healing time is >3 weeks o Wounds subjected to a prolonged inflammation, whether due to a foreign body, infection, burn or inadequate wound closure o Areas of chronic inflammation, e.g. earring site o Also, rare spontaneous keloids without history may occur After the initial insult to the skin + formation of a clot, the balance between granulation tissue degradation + tissue biosynthesis = key to adequate healing o Keloids have an increased blood vessel density, a thickened epidermal layer, and increased mucous ground substance o The presence of myofibroblasts are also important for contraction of scars, and these a few/not present in keloids The collagen fibrils in keloids are more irregularly + abnormally thick o Biochemical differences in collagen content in normal scars + keyloids have been examined in numerous studies o Collagen synthesis is 20x > normal scars, but cross links in normal scars > keloids (scars are less stable) These changes seem to be mediated by cytokines: o Keloids demonstrate an amplified production of TNF-alpha, INF-beta + IL-6 o Also diminished production of INF-alpha, INF-gamma + TNF-beta The abnormal cytokine production is possibly due to genetic predispositions involving HLA + blood group A; however there is no consistent pattern NB: Why do foetuses heal without scarring? Sterile amniotic fluid Rapid epithelialization More HA Nonsulfated GAGs TGF 3 isoform More fibroblast migration High proportion PCIII 33