Recent Advances in Localized Scleroderma

Localized scleroderma (LSc), or morphea, is an autoimmune connective tissue disease causing inflammation and fibrosis of the skin and underlying tissues. While distinct from systemic sclerosis, its clinical presentation is highly diverse. This review summarizes recent advances in the understanding and management of LSc. Pathophysiological insights have evolved significantly; the somatic mosaicism hypothesis is now supported by the observation of all six of Happle’s classic lesion patterns in LSc. Furthermore, recent single-cell RNA sequencing has elucidated key cellular mechanisms, revealing an IFN-γ-driven pro-fibrotic crosstalk between T cells, dendritic cells, and specific inflammatory fibroblast subpopulations. The discovery of a rare monogenic form of LSc caused by a STAT4 gain-of-function mutation provides a powerful human model, solidifying the critical role of the JAK-STAT pathway. Clinically, LSc is classified into subtypes such as circumscribed, linear, and generalized morphea. Extracutaneous manifestations are common, particularly in juvenile LSc, and are associated with higher disease activity and reduced quality of life, necessitating a multidisciplinary approach. Management is becoming standardized, with methotrexate as the first-line systemic therapy for severe disease. For refractory cases, targeted treatments including abatacept, tocilizumab, and JAK inhibitors are emerging as promising options. In addition, reconstructive therapies like autologous fat grafting are crucial for managing atrophic sequelae. These recent advances are paving the way for more effective, targeted therapies to improve outcomes for patients with this complex disease.