Dermatomyositis

Dermatomyositis (DM) is a rare idiopathic inflammatory myopathy characterized by distinctive skin manifestations and symmetric proximal muscle weakness. It can occur in both children (juvenile dermatomyositis, ICD-10: M33.0) and adults (ICD-10: M33.1). The disease affects the skin, skeletal muscles, and potentially other organ systems including the lungs, heart, gastrointestinal tract, and joints. Hallmark cutaneous features include a heliotrope rash (violaceous discoloration of the eyelids), Gottron papules (erythematous or violaceous papules over the knuckles and extensor surfaces), the shawl sign, and V-sign rash on the anterior chest. Proximal muscle weakness typically manifests as difficulty climbing stairs, rising from a seated position, or lifting the arms overhead. Some patients develop clinically amyopathic dermatomyositis, where characteristic skin findings are present without significant muscle involvement. Dermatomyositis is considered an autoimmune condition in which the immune system attacks small blood vessels (capillaries) in the muscles and skin, leading to a complement-mediated microangiopathy. Myositis-specific autoantibodies (such as anti-Mi-2, anti-MDA5, anti-NXP2, anti-TIF1-gamma, and anti-SAE) are found in many patients and help define clinical subsets with distinct prognoses and complications. Interstitial lung disease is a significant complication, particularly in patients with anti-MDA5 antibodies. In adults, dermatomyositis is associated with an increased risk of malignancy, particularly in the first few years after diagnosis, necessitating age-appropriate cancer screening. Treatment typically involves systemic corticosteroids (such as prednisone) as first-line therapy, often combined with steroid-sparing immunosuppressive agents including methotrexate, azathioprine, mycophenolate mofetil, or intravenous immunoglobulin (IVIG). IVIG has demonstrated efficacy in randomized controlled trials and is increasingly used as a primary or adjunctive therapy. For refractory cases, rituximab and other biologic agents may be considered. Photoprotection and topical therapies are important for managing skin disease. Physical therapy and rehabilitation play a crucial role in maintaining muscle strength and function. With appropriate treatment, many patients achieve significant improvement, though the disease may follow a chronic or relapsing course.

Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.

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