Background Diagnostic criteria are used to identify a patient having a disease in a clinical setting, whereas classification criteria create a well-defined population for research purposes. The diagnosis and classification of amyopathic dermatomyositis (ADM) have not been recognized by most existing criteria for idiopathic inflammatory myopathies (IIMs). To address this, several criteria were proposed to define ADM either as a distinct disease entity or as a subset of the spectrum of IIMs. Objectives To discuss the diagnosis and classification of ADM and to assesses the available criteria in identifying cases of ADM and/or distinguishing it from dermatological mimickers such as lupus erythematosus. Methods We conducted an extensive literature search using the PubMed database from June 2016 to August 2018, using the search terms 'amyopathic dermatomyositis', 'diagnosis' and 'classification'. Results The European League Against Rheumatism (EULAR)/American College of Rheumatology (ACR) criteria, which are the only validated classification criteria for adult and juvenile IIM and their major subgroups, include three cutaneous items (G€ ottron sign, G€ ottron papules, heliotrope rash) to be able to classify ADM. This international and multispecialty effort is a huge step forward in the classification of skin-predominant disease in dermatomyositis. However, about 25% of the population with ADM do not meet two out of the three skin features and are misdiagnosed or classified as having a different disease entity, most commonly lupus erythematosus. Conclusions These gaps rationalize the continuous assessment and improvement of existing criteria and/or the development of validated, separate and skin-focused criteria for DM. What's already known about this topic?• The diagnosis and classification of amyopathic dermatomyositis (ADM) have not been recognized by most existing criteria for idiopathic inflammatory myopathies (IIMs).• The latest validated European League Against Rheumatism (EULAR)/American College of Rheumatology (ACR) criteria perform well in capturing the majority of the ADM population using three skin variables: G€ ottron sign, G€ ottron papules and heliotrope rash.• However, about 25% of patients with ADM do not meet two out of the three skin features and fail the classification.What does this study add?• The gaps in the existing classification and diagnostic criteria for IIMs rationalize the continuous assessment and improvement of existing criteria and/or the development of validated and skin-focused criteria for DM. Diagnosis and classification of amyopathic dermatomyositis, J.S.S. Concha et al. 1003Heliotrope rash, G€ ottron papules, G€ ottron sign Heliotrope rash (blue-purple discoloration on the upper eyelids with or without associated oedema) Erythematous rash on the face, neck, anterior chest (V-sign) or back and shoulders (shawl sign), knees, elbows and malleoli Mechanic's hands (rough and cracked lateral and palmar areas of the fingers) Photosensitivity and pruritus

Pemphigus, an autoimmune blistering disease that affects the skin and mucous membranes, adversely impacts patients' quality of life (QOL). While there are various QOL measurement tools that can be used in this disease, few studies have assessed how a patient's change in disease severity can affect their QOL. This study aims to identify which disease severity index correlates best with the change in QOL. Fifty pemphigus patients completed QOL surveys with disease severity scored over two visits. QOL was assessed with the Autoimmune Bullous Disease Quality of Life (ABQOL), Dermatology Life Quality Index (DLQI), Skindex-29, and Short Form Survey 36 (SF-36). Disease severity was scored with the Pemphigus Disease Area Index (PDAI) and Autoimmune Bullous Skin Disorder Intensity Score (ABSIS). Correlations between the change in QOL scores and change in disease severity were analyzed using Spearman's coefficient (r). The change in PDAI showed a strong correlation (r = 0.60–0.79) with changes in the ABQOL, Skindex-29 symptoms (Skindex-S), and Skindex-29 functioning (Skindex-F) subscales for all patients (n = 50). For patients with mucosal disease (n = 24), the change in PDAI showed a strong correlation with changes in the ABQOL and Skindex-S subscale. For patients without mucosal disease, the change in PDAI showed a strong correlation with the Skindex-S. The change in ABSIS showed a strong correlation with Skindex-S for all patients and patients with no mucosal involvement, but showed no strong correlations for patients with mucosal involvement. The changes in PDAI always had a stronger correlation than the changes in ABSIS scores to changes in the ABQOL, DLQI, and Skindex-29 subscales, except where the PDAI and ABSIS scores were about the same for the Skindex-S subscale in patients with no mucosal involvement (r = 0.76 and r = 0.77, respectively). PDAI is superior to ABSIS in its correlation with validated QOL tools. The QOL tools that appear to be of most use in clinical trials and patient management are the Skindex-S and ABQOL.

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.