References1 Concha JSS, Pena S, Gaffney RG et al.; Skin Myositis Delphi Group. Developing classification criteria for skin-predominant dermatomyositis: the Delphi process. Br J Dermatol 2020; 182: 410-7. 2 Concha JSS, Tarazi M, Kushner CJ et al. The diagnosis and classification of amyopathic dermatomyositis: a historical review and assessment of existing criteria. Br J Dermatol 2019; 180:1001-8. 3 Lundberg IE, Tj€ arnlund A, Bottai M et al.; International Myositis Classification Criteria Project Consortium, the Euromyositis Register, and the Juvenile Dermatomyositis Cohort Biomarker Study and Repository (UK and Ireland). 2017 European League Against Rheumatism/American College of Rheumatology Classification Criteria for adult and juvenile idiopathic inflammatory myopathies and their major subgroups. Arthritis Rheumatol 2017; 69:2271-82. 4 Patel B, Khan N, Werth VP. Applicability of EULAR/ACR classification criteria for dermatomyositis to amyopathic disease. J Am Acad Dermatol 2018; 79:77-83.e1. 5 Gerami P, Schope JM, McDonald L et al. A systematic review of adult-onset clinically amyopathic dermatomyositis (dermatomyositis sine myositis): a missing link within the spectrum of the idiopathic inflammatory myopathies. References 1 Kim HS, Lee S, Kim JH. Real-world evidence versus randomized controlled trial: clinical research based on electronic medical records. J Korean Med Sci 2018; 33:e213. 2 Suvarna VR. Real world evidence (RWE)are we (RWE) ready? Perspect Clin Res 2018; 9:61-3. 3 de Wijs LEM, Bosma AL, Erler NS et al. Effectiveness of dupilumab treatment in 95 patients with atopic dermatitis: daily practice data. Br J Dermatol 2020; 182:418-26. 4 Simpson EL, Bieber T, Guttman-Yassky E et al. Two phase 3 trials of dupilumab versus placebo in atopic dermatitis. N Engl J Med 2016; 375:2335-48.

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Summary Background The European League Against Rheumatism/American College of Rheumatology classification criteria for inflammatory myopathies are able to classify patients with skin‐predominant dermatomyositis (DM). However, approximately 25% of patients with skin‐predominant DM do not meet two of the three hallmark skin signs and fail to meet the criteria. Objectives To develop a set of skin‐focused classification criteria that will distinguish cutaneous DM from mimickers and allow a more inclusive definition of skin‐predominant disease. Methods An extensive literature review was done to generate items for the Delphi process. Items were grouped into categories of distribution, morphology, symptoms, antibodies, histology and contextual factors. Using REDCap™, participants rated these items in terms of appropriateness and distinguishing ability from mimickers. The relevance score ranged from 1 to 100, and the median score determined a rank‐ordered list. A prespecified median score cut‐off was decided by the steering committee and the participants. There was a pre‐Delphi and two rounds of actual Delphi. Results There were 50 participating dermatologists and rheumatologists from North America, South America, Europe and Asia. After a cut‐off score of 70 during the first round, 37 of the initial 54 items were retained and carried over to the next round. The cut‐off was raised to 80 during round two and a list of 25 items was generated. Conclusions This project is a key step in the development of prospectively validated classification criteria that will create a more inclusive population of patients with DM for clinical research. What's already known about this topic? Proper classification of patients with skin‐predominant dermatomyositis (DM) is indispensable in the appropriate conduct of clinical/translational research in the field. The only validated European League Against Rheumatism/American College of Rheumatology criteria for idiopathic inflammatory myopathies are able to classify skin‐predominant DM. However, a quarter of amyopathic patients still fail the criteria and does not meet the disease classification. What does this study add? A list of 25 potential criteria divided into categories of distribution, morphology, symptomatology, pathology and contextual factors has been generated after several rounds of consensus exercise among experts in the field of DM. This Delphi project is a prerequisite to the development of a validated classification criteria set for skin‐predominant DM.

CLASI activity measurement showed excellent inter- and intrarater reliability in paediatric CLE and superiority over the PGA. These results demonstrate that the CLASI is a reliable and valid outcome instrument for paediatric CLE.