From the Guidelines
Dermatomyositis has several distinct clinical variants, including classic adult dermatomyositis, juvenile dermatomyositis, amyopathic dermatomyositis, hypomyopathic dermatomyositis, cancer-associated dermatomyositis, anti-synthetase syndrome, inclusion body myositis with dermatomyositis features, and drug-induced dermatomyositis. The classic adult dermatomyositis presents with proximal muscle weakness and characteristic skin findings including Gottron's papules, heliotrope rash, and photosensitive eruptions 1. Juvenile dermatomyositis affects children under 18 years and often includes calcinosis cutis and vasculopathy, with diagnostic criteria under revision to incorporate new outcome tools, especially autoantibodies and biomarkers 1. Amyopathic dermatomyositis features typical skin manifestations without clinically significant muscle involvement, though these patients may have an increased risk of interstitial lung disease 1. Hypomyopathic dermatomyositis presents with minimal muscle weakness and normal or slightly elevated muscle enzymes 1. Cancer-associated dermatomyositis occurs in approximately 20-25% of adult cases and requires thorough malignancy screening 1. Anti-synthetase syndrome is characterized by myositis, interstitial lung disease, arthritis, mechanic's hands, Raynaud's phenomenon, and fever, associated with anti-aminoacyl-tRNA synthetase antibodies 1. Inclusion body myositis with dermatomyositis features combines inflammatory myopathy with inclusion bodies on muscle biopsy 1. Drug-induced dermatomyositis can be triggered by medications like hydroxyurea, statins, and TNF inhibitors 1. Some key points to consider in the management of these variants include:
- The use of high-dose corticosteroids concurrent with a steroid-sparing agent for adult patients with idiopathic inflammatory myositis 1
- The importance of treating skin disease aggressively in juvenile dermatomyositis, as it is associated with high morbidity 1
- The need for close monitoring of patients' disease status and well-being by an experienced multidisciplinary team for a good clinical outcome 1
- The potential use of novel biomarkers of disease activity, such as interleukin 6 and type 1 interferon-regulated genes, as indicators of disease activity in adult and juvenile myositis 1
From the Research
Clinical Variants of Dermatomyositis
The clinical variants of dermatomyositis include:
- Classic dermatomyositis
- Clinically amyopathic dermatomyositis (CADM)
- Paraneoplastic dermatomyositis
- Juvenile dermatomyositis
Characteristics of Each Variant
- Classic Dermatomyositis: characterized by skin features such as heliotrope rash and violaceous papules, and muscle involvement with symmetrical weakness of the proximal muscles 2
- Clinically Amyopathic Dermatomyositis (CADM): characterized by typical DM cutaneous manifestations but without myositis, with a relative paucity of characterized cases in the peer-reviewed medical literature 3
- Paraneoplastic Dermatomyositis: associated with a wide range of solid or hematologic malignancies, with distinct serotypes related to specific phenotypes and clinical features 2
- Juvenile Dermatomyositis: characterized by a higher frequency of neck muscle involvement, subcutaneous calcifications, and better outcomes compared to adult DM 4
Disease Progression and Outcomes
- Classic DM: 40% of patients may become postmyopathic, with continued muscle disease and moderate/severe skin disease 5
- CADM: low risk of progressing to muscle disease, with the extent of skin disease as a potential predictive factor 5
- Juvenile DM: better outcomes compared to adult DM, with distinctive characteristics such as higher frequency of neck muscle involvement and subcutaneous calcifications 4