A new proposal for phenotypic classification and outcome assessment of dermatomyositis based on clinical manifestations and serological testing.

BACKGROUND: Dermatomyositis (DM) is an infrequent disease subgroup of idiopathic inflammatory myopathies characterized by distinct skin lesions. However, high heterogeneity makes clinical diagnosis and treatment of DM very challenging. OBJECTIVES: Unsupervised classification in DM patients and analysis of key factors related to clinical outcomes. METHODS: This retrospective study was conducted between 2017 and 2022 at the Department of Rheumatology, Xiangya Hospital, Central South University. 162 DM patients were enrolled for unsupervised hierarchical cluster analysis. In addition, we divided the clinical outcomes of DM patients into four subgroups: withdrawal, stabilization, aggravation, and death, and compared the clinical profiles amongst the subgroups. RESULTS: Out of 162 DM patients, three clusters were defined. Cluster 1 (n = 40) was mainly grouped by patients with prominent muscular involvement and mild Interstitial Lung Disease (ILD). Cluster 2 (n = 72) grouped patients with skin rash, anti-Melanoma Differentiation Associated protein 5 positive (anti-MDA5+), and Rapid Progressive Interstitial Lung Disease (RP-ILD). Cluster 3 (n = 50) grouped patients with the mildest symptoms. The proportion of death increased across the three clusters (cluster 3 < cluster 1 < cluster 2). STUDY LIMITATIONS: The number of cases was limited for the subsequent construction and validation of predictive models. We did not review all skin symptoms or pathological changes in detail. CONCLUSIONS: We reclassified DM into three clusters with different risks for poor outcome based on diverse clinical profiles. Clinical serological testing and cluster analysis are necessary to help clinicians evaluate patients during follow-up and conduct phenotype-based personalized care in DM.

The diagnosis and classification of amyopathic dermatomyositis: a historical review and assessment of existing criteria.

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 (Göttron sign, Göttron 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.

Classifying idiopathic inflammatory myopathies: comparing the performance of six existing criteria.

OBJECTIVES: Various criteria have been proposed to classify the inflammatory myositides (IIMs) polymyositis (PM) and dermatomyositis (DM). However, none have received universal acceptance. Our aim was to assess the performance of the main criteria used to classify IIM. Specialist consultant diagnosis was considered the gold standard. METHODS: Patients attending King's College Hospital (KCH) or Reggio Emilia Hospital (REH) since 1990 with a diagnosis of IIM or non-inflammatory myopathy were identified, and their records and laboratory investigations retrospectively reviewed. Where the complete data required for the classification criteria or a final physician diagnosis was unavailable, patients were excluded. 52 patients with a specialist diagnosis of PM, DM, inclusion body myositis (IBM) or non-inflammatory myopathy were included. Agreement between specialist consultant diagnosis and classification criteria was measured using Cohen's kappa (κ) statistics. Sensitivity and specificity were also calculated. RESULTS: The Dalakas (2003) criteria demonstrated substantial agreement with specialist diagnosis: κ=0.69, sensitivity 77%, specificity 99%. The European Neuromuscular Centre criteria (ENMC) demonstrated fair agreement: κ=0.49, sensitivity 71%, specificity 82%. Other criteria performed less well. In particular, the Bohan and Peter criteria demonstrated a specificity of only 29%. CONCLUSIONS: The criteria of Dalakas (2003) agreed best with specialist consultant diagnosis. The criteria of Bohan and Peter demonstrated very poor specificity. Prospective studies are required to develop improved classification criteria.

Review of the classification and assessment of the cutaneous manifestations of the idiopathic inflammatory myopathies.

Adult and juvenile dermatomyositis, polymyositis and myositis overlapping with another connective tissue disease are rare systemic autoimmune diseases with a primary feature of weakness and muscle inflammation. Cutaneous findings specific to the underlying condition are present in many patients with these disorders. Some lesions are highly characteristic of the idiopathic inflammatory myopathies (IIM), especially in dermatomyositis. Some cutaneous findings are common but not specific to the IIM and others are less frequently observed in patients with these illnesses. Many of these manifestations also have different grades of disease activity or damage. This photoessay reviews the classification and assessment of the cutaneous manifestations of the IIM and presents example photographs of many of the lesions of adult and juvenile IIM accumulated from the clinical experience of international experts in these conditions. The purpose of this work is to facilitate better recognition of the diverse cutaneous manifestations associated with these inflammatory myopathies.