Systemic sclerosis complicated with localized scleroderma-like lesions induced by Köbner phenomenon

Background: Scleroderma is a chronic disease of unknown etiology characterized by skin fibrosis and is divided into two clinical entities: systemic sclerosis (SSc) and localized scleroderma (LSc). In general, LSc is rarely complicated with SSc, but a certain portion of SSc patients manifests bilateral symmetric LSc-like lesions on the trunk and extremities. Objective: We investigated SSc patients with LSc-like lesions to clarify the underlying pathophysiology. Methods: Nine SSc cases complicated with LSc-like lesions were clinically and histologically characterized. Results: SSc patients with LSc-like lesions exhibited multiple progressive hyper- and/or hypo-pigmented plaques with mild sclerosis symmetrically distributed on the trunk and extremities, especially abdominal region. In histological assessment, epidermal IL-1α expression was elevated in both forearms and LSc-like lesions of these patients to a greater extent than in forearms of control patients (SSc patients without LSc-like lesions). Of note, the infiltration and degranulation of mast cells were evident throughout the dermis of LSc-like lesions, while detectable to a lesser extent in forearms of SSc patients with LSc-like lesions and control patients. Conclusion: The epidermis of SSc patients with LSc-like lesions seems to possess an inflammatory phenotype, leading to the activation of mast cells in the dermis of mechanically stressed skin. Köbner phenomenon may be involved in the induction of LSc-like lesions in a certain subset of SSc.