الفهرس 
Keloids and hypertrophic scarsOnly 14 pages are availabe for public view
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Abstract
Keloids and hypertrophic scars are dermal fibroproliferative disorders that usually develop after healing of a skin injury, although keloids sometimes occur spontaneously.
Clinically, Keloids initially manifest as raised erythematous lesions that become pale as they age, extending beyond the original wound borders, do not usually regress spontaneously and tend to recur after excision. On the other hand, hypertrophic scars are raised erythematous fibrous lesions that remain within the confines of the original wound and usually undergo partial spontaneous resolution with time.
In addition to the clinical differences between keloids and hypertrophic scars, each has unique histological appearance. Keloids are characterized by haphazard deposition of thick, hyalinized eosinophilic collagen bundles within the dermis with abundant mucinous mucopolysaccharide ground substance. The collagen bundles form nodules that contain an abundance of eosinophils, mast cells, plasma cells and lymphocytes. Hypertrophic scars also demonstrate increased collagen bundles but are less clearly demarcated and lack the hyalinized appearance noted with keloids. Moreover, they remain parallel to the epithelial surface as observed with normal skin. In addition, hypertrophic scars show myofibroblasts with α smooth muscle actin expression believed to be important in the pathogenesis of contractures.
The aetiopathogenesis of keloids and hypertrophic scars is not completely understood. Predisposing factors include trauma, skin tension, foreign body, infection, immunological factors, hormonal factors, hypoxia and genetic predisposition. These result in increased fibroblasts proliferation; responsible for enhanced collagen production and excessive scarring.
Keloids and hypertrophic scars represent a major therapeutic dilemma to the dermatologists. As enhanced collagen production represents the main frame for the pathogenesis of both conditions, the various treatment methods aim at breakage or removal of the overformed collagen. These methods include surgical, non surgical as well as combined treatments. Surgical treatment includes surgical excision, cryotherapy and laser treatment. Non surgical treatment includes intralesional steroid, radiation therapy, silicon gel sheeting and pharmacological treatment. Combined treatment represents combination of intralesional steroid with surgery, cryotherapy or laser treatment.
Cryotherapy has been used to treat skin lesions for approximately 100 years. Liquid nitrogen is currently the most widely used cryogen. Tissue injury by freezing arises from direct cell injury caused by ice crystal formation, microcirculatory failure which occurs in the thawing period and stimulation of immune response. Over the last years, several studies have proved cryosurgery to be an effective and safe therapeutic regimen for keloids and hypertrophic scars either as monotherapy or in combination with other treatment regimens. The protocol used varied from one to three freeze-thaw cycles, 10-30 seconds each, with 1mm margin and with repetition of the session every 20-30 days when needed. The number of sessions and the duration of lesions correlate significantly with the results of the treatment.
Intralesional injection represents an important part of dermatologic therapy since first introduced in 1961. The rationale for intralesional therapy is to deliver a medication directly into a specific skin lesion to treat local tissues with minimal systemic effects. TAC is the most commonly used intralesional drug. Intralesional TAC has been claimed to be the most effective therapy in treatment of keloids and hypertrophic scars. It inhibits collagen synthesis in addition to its anti- inflammatory properties. It can be used either as monotherapy or in combination with other therapies in concentrations of 10-40 mg/ml, 3-4 weeks apart. Cryotherapy was advocated to be used prior to intralesional TAC in order to induce tissue oedema to facilitate intralesional injections. Combination of cryotherapy and intralesional steroid injection produced a higher success rate and a lower recurrence rate.
Advances in laser techniques over last years have increased both safety and popularity of laser use in dermatology. Skin-ablative laser systems as Er:YAG and CO2 lasers; as well as vascular destroying laser systems as PDL and Nd:YAG laser have established themselves in the treatment of keloids and hypertrophic scars.
The Er:YAG laser contains a YAG crystal doped with erbium gas and excited by a pulsed flashlamp that emits light at a shorter wavelength of 2490 nm which corresponds to a peak in water absorption. This property allows Er:YAG laser to be effective in treatment of keloids and hypertrophic scars. Moreover, Er:YAG laser has a very short pulse duration, which further limits damage to surrounding areas, in addition to finer ablation and shortened healing time in comparison to CO2 laser.
In our study, we compared cryotherapy combined with intralesional TAC with Er:YAG laser in treatment of keloids and hypertrophic scars. The comparison included clinical response, number of sessions, recurrence of lesions, side effects and feasibility of either technique.
The study included 10 patients (3 males and 7 females) with mean age 25.5±8 years (19-35). They had different sized keloids and hypertrophic scars. Five patients (group A) were subjected to cryotherapy with liquid nitrogen 15 seconds’ freeze-thaw cycle followed by intralesional injection of TAC 2mg/cm2. The other five patients (group B) were treated with ablative Er:YAG laser 2940 nm. Patients of the 1st group were subjected to 1-5 sessions three weeks apart, while patients of the 2nd group received 1-2 sessions four weeks apart.
A higher clinical response; evaluated by the comparison of patient׳s photographs, patient׳s satisfaction and reduction in the lesion thickness measured by an external caliber was found with cryotherapy combined with intralesional TAC. This may be related to the higher number of treatment sessions received by those patients. As regards Er:YAG laser; apart from one patient who performed 2nd session, the other four patients refused to be subjected to further sessions, due to the associated prolonged healing periods after the 1st session and the other complications encountered. No recurrence of the lesions was associated with cryotherapy combined with intralesional TAC while with Er:YAG laser, two patients showed recurrence of their lesions within three months of treatment. One of them showed 100% recurrence of the lesion and the other showed 50% recurrence of the lesion.
In conclusion to this study, we found that cryotherapy combined with intralesional TAC is a simple economic procedure that gives a higher clinical response, lower rate of recurrence and fewer side effects, making it an attractive option whenever available. On the other hand, laser needs a special apparatus, is associated with an open wound that necessitates special care and needs a higher cost.