6. Needle-free electronically-controlled jet injector treatment with bleomycin and lidocaine is effective and welltolerated in patients with recalcitrant keloids. 147 6. INTRODUCTION Keloids are hyperproliferative scars that extend beyond the confines of the original wound or trauma and are caused by chronic localized dermal inflammation.1, 2 Keloids can cause both physical and psychosocial distress.3 The Quality of Life (QoL) of patients can be severely affected by symptoms such as pain, pruritus, functional impairment and physical appearance.4 Keloidal scars are characterized by an overproduction of extracellular matrix components, including collagen, elastin, fibronectin, and proteoglycans.5 The pathogenesis of keloid scars is not completely understood and entails a combination of genetic and environmental factors, with a higher incidence observed among individuals with darker skin tones.6-8 Current hypotheses suggest that the reticular dermis plays a vital role in the development of these scars.9 Trauma or inflammation of the skin can trigger a chronic low grade inflammatory response within this part of the dermis.2 This inflammatory response involves activation of fibroblasts and a number of cytokines, including IL-6, IL-8, and IL-10, alongside several growth factors. Subsequently, the activation of fibroblasts induces neovascularization and increased deposition of collagen, ultimately leading to keloid formation.10 The first line treatment of keloids consists of intralesional needle injections with corticosteroids.11 Unfortunately, these injections often cause significant procedure related pain and are unsuitable for patients with needle phobia, which occurs in up to 30% of young adults.9 Furthermore, the firm consistency of the keloid can hamper the intralesional delivery of drugs and may lead to reduced effectiveness.12 Although treatment with corticosteroids is effective in most patients, there is a high risk for recurrences, which are reported to occur in up to 50% of patients after 12 months.13 Finally, some patients do not respond to intralesional corticosteroid injections.14 These limitations underline the need for more effective, safe, and patientfriendly treatment options with long-lasting benefit in this difficult to treat population. Needle-free electronically controlled pneumatic jet injectors (EPI) are an innovative and less painful alternative for intralesional injections with conventional needles.15 These devices create a high-velocity fluid stream that penetrates the epidermis to inject drugs
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