Importance: Numerous classification systems for morphea subtypes exist, but none have been systematically evaluated for their ability to categorize patients with morphea into demographically and clinically coherent groups. Although some subtypes, such as linear morphea, are present across all the classification schemes, others list unique subtypes. This creates confusion among investigators and practitioners and impairs accurate categorization of patients for study and clinical evaluation. Objective: To evaluate how frequently the commonly used morphea classification systems categorize patients with morphea into clinically relevant subtypes using cross-sectional analysis of 2 large patient cohorts. Design, Setting, and Participants: This cross-sectional study comprised 944 adults and children from 2 prospective cohorts - the Morphea in Adults and Children at the University of Texas Southwestern Medical Center (Dallas, Texas), which enrolled participants from July 20, 2007, to September 21, 2018, and the National Registry for Childhood-Onset Scleroderma at the University of Pittsburgh (Pittsburgh, Pennsylvania), which enrolled participants from October 23, 2002, to November 13, 2018. Main Outcomes and Measures: Patient demographic characteristics, morphea subtype, quality-of-life measures, disease activity, and damage as measured by Localized Scleroderma Cutaneous Assessment Tool scores during initial visits. Results: A total of 944 participants (444 patients with adult-onset morphea and 500 patients with pediatric-onset morphea; 741 female participants [78%]; median age at onset, 16 years [interquartile range, 8-44 years]) were included in this study. Most participants were White (723 [77%]) and had the linear (474 [50%]) or generalized subtype of morphea (244 [26%]). With the use of the previously published Padua criteria, most patients were classified to have linear morphea (474 [50%]), followed by generalized morphea (244 [26%]), plaque morphea (141 [15%]), mixed morphea (38 [4%]), and pansclerotic morphea (3 [0.3%]). Overall, the Padua criteria successfully classified 900 patients (95%) in comparison with the Peterson criteria (533 [56%]) and the European Dermatology Forum classification (487 [52%]). Conclusions and Relevance: In this cross-sectional study of morphea subtype classification systems, the Padua criteria performed best in classifying patients into subgroups with cohesive demographic and clinical features, supporting its widespread use. However, they have ambiguities that might lead to misclassification, particularly in terms of generalized and pansclerotic morphea and descriptors such as morphea profunda. Consensus-based approaches are needed to address these ambiguities and develop a unified classification scheme..
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