Abstract

Adult and juvenile dermatomyositis share the hallmark features of pathognomic skin rash and muscle inflammation, but are heterogeneous disorders with a range of additional disease features and complications. The frequency of important clinical features such as calcinosis, interstitial lung disease and malignancy varies markedly between adult and juvenile disease. These differences may reflect different disease triggers between children and adults, but whilst various viral and other environmental triggers have been implicated, results are so far conflicting. Myositis-specific autoantibodies can be detected in both adults and children with idiopathic inflammatory myopathies. They are associated with specific disease phenotypes and complications, and divide patients into clinically homogenous subgroups. Interestingly, whilst the same autoantibodies are found in both adults and children, the disease features remain different within autoantibody subgroups, particularly with regard to life-threatening disease associations, such as malignancy and rapidly progressive interstitial lung disease. Our understanding of the mechanisms that underlie these differences is limited by a lack of studies directly comparing adults and children. Dermatomyositis is an autoimmune disease, which is believed to develop as a result of an environmental trigger in a genetically predisposed individual. Age-specific host immune responses and muscle physiology may be additional complicating factors that have significant impact on disease presentation. Further study into this area may produce new insights into disease pathogenesis.

Highlights

  • Dermatomyositis (DM) is an idiopathic inflammatory myopathy, characteristic features of which are inflammation of skeletal muscle causing weakness, and pathognomic skin rashes, including periorbital heliotrope discoloration and Gottron’s papules

  • juvenile DM (JDM) is the most common of the childhood idiopathic inflammatory myopathies, whereas in adults polymyositis is more common than DM in Caucasian populations

  • Whilst adult DM and JDM share the hallmark disease characteristics of classical rash and muscle weakness, the frequency of other disease features varies with age of onset

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Summary

Introduction

Dermatomyositis (DM) is an idiopathic inflammatory myopathy, characteristic features of which are inflammation of skeletal muscle causing weakness, and pathognomic skin rashes, including periorbital heliotrope discoloration and Gottron’s papules. Anti-MDA5 has been identified in Japanese children with JDM and rapidly progressive lung disease and was associated with a poor response to treatment and increased mortality [62]. This autoantibody has not been identified in JDM cohorts to date [63]. The association between the HLA 8.1 haplotype has been shown to be stronger in certain autoantibody subgroups, namely anti-Jo1 and anti-PmScl [81] These data show that genetic background modifies clinical presentation; results from a recently completed, genome-wide association study of adult DM and JDM may shed light on other important loci implicated in pathogenesis [33]. Given the potentially different aetiologies of malignancy-associated and non-malignancy-associated DM, it would be interesting to compare the genetic background of these two groups

Conclusion
Findings
Bendewald MJ
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