The skin myositis Delphi group puts the details in 'skin-predominant' dermatomyositis.

In this issue of the BJD, the Skin Myositis Delphi Group describes the efforts of physicians who have united to resolve an important dermatological question – what really defines skin‐predominant dermatomyositis?1 Acceptance of skin‐predominant/amyopathic dermatomyositis (ADM) as a true dermatomyositis (DM) subtype has taken a considerable amount of time and effort on the part of dermatologists.2 However, the perseverance of a dedicated group of dermatologists has culminated in ADM being included as a recognized DM subtype in the recently validated 2017 European League Against Rheumatism/American College of Rheumatology (EULAR/ACR) classification criteria for idiopathic inflammatory myopathies (IIM).3 The 2017 EULAR/ACR criteria include three DM‐associated skin manifestations to classify ADM: Göttron sign, Göttron papules and heliotrope rash. By using the EULAR/ACR classification criteria, patients with these pathognomonic skin manifestations of juvenile and adult DM were accurately classified without including muscle biopsy data.

Although the inclusion of ADM is a huge victory for dermatologists and other specialists who frequently diagnose and/or treat these patients, the 2017 EULAR/ACR IIM criteria for ADM are not perfect. Recent work by Dr Victoria Werth, has shown that up to 26% of patients with ADM still fail to meet the diagnostic criteria set forth in the 2017 EULAR/ACR IIM classification.4 Additional work has also shown a significant percentage of patients with skin‐predominant ADM are misdiagnosed as having cutaneous lupus erythematosus.5, 6 Failure to appropriately diagnose these patients as having DM is concerning for several reasons. For one, a misdiagnosis may lead to significant delays in screening appropriate patients for associated underlying comorbid conditions, including interstitial lung disease or visceral malignancies. Secondly, misdiagnosis implies that more than 25% of patients with skin‐predominant DM may fail to be included in research efforts, including clinical trials, aiming to better understand and treat patients with DM.

To improve the classification criteria for skin‐predominant DM and minimize the chances of misdiagnosis, the Skin Myositis Delphi Group, led by Dr Werth and several others, developed an extensive list of items seen in patients with DM in terms of distribution, morphology, symptoms, antibodies, histology and contextual factors, and invited 50 dermatologists and rheumatologists with expertise in DM from around the world to participate in several Delphi rounds to determine a consensus concerning those factors which are thought to be most important for a classification criteria in diagnosing skin‐predominant DM. These efforts, which are detailed in this issue of the BJD, have resulted in a list of 25 potential criteria in the above categories that will be subjected to further validation in prospective testing.1

The findings in this manuscript represent a tremendous amount of work over several years by Dr Werth and colleagues, all in the name of ensuring that this subset of patients with DM have the same opportunities for screening, therapeutic intervention and enrolment in clinical trials testing cutting‐edge medications as patients with classic DM. Importantly, the goal is not to replace the 2017 EULAR/ACR criteria, which are adequate in classifying ADM, but, if prospectively validated, these classification criteria may be complementary and utilized if there is a high index of suspicion of DM in a patient who does not meet the EULAR/ACR criteria for ADM. This work is yet another example of the positive impact that dermatologists from around the world can have on patients with systemic diseases that may be seen and treated by a variety of medical specialists. These efforts not only should be of interest to those who treat patients with DM, but also will hopefully stimulate similar work by dermatologists for other diseases that may be systemic in nature, but have skin‐predominant subtypes.

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