9th June 2025

Dermatomyositis

Dermatomyositis is an inflammatory myopathy with characteristic cutaneous manifestations. The condition is often linked to cancer. 

Clinical features 

Approximately 80% of patients have myopathy, with patients exhibiting symmetrical, proximal muscle weakness. Dermatomyositis is, however, differentiated from polymyositis by the characteristic cutaneous signs:

• Gottron papules 
• Heliotrope oedema of the eyelids 
• Periungual telangiectasia 
• Poikiloderma
• Photo distributed erythema 
• Scaly alopecia
• Calcinosis cutis

Image Source: Wikimedia Commons (2018). Gottron Papules Dermatomyocitis, Licensed under a creative commons licence. Available for free at: https://commons.wikimedia.org/w/index.php?search=Gottron_papules_.dermatomyocitis.jpg&title=Special%3ASearch&profile=advanced&fulltext=1&ns0=1&ns6=1&ns12=1&ns14=1&ns100=1&ns106=1 (Accessed 23 May 2025).

Image Source: Wikimedia Commons (2017). Dermatomyocitis9, Licensed under a creative commons licence. Available for free at:  https://commons.wikimedia.org/wiki/File:Dermatomyositis9.jpg (Accessed 23 May 2025).

Dermatomyositis is associated with a 6 times increased risk of malignancy, with the following cancer types most reported:

• Ovarian
• Lung
• Pancreatic
• Breast
• Gastric
• Nasopharyngeal

Diagnosis

The diagnosis of dermatomyositis is complex with many criteria such as the “Bohan and Peter criteria” being proposed. In general, the following features are present:

• Symmetrical muscle weakness
• Elevation of muscle enzymes: High creatinine kinase levels is a sensitive but not a specific marker
• Presence of autoantibodies: in particular, Myositis Specific Antibodies being present in approximately 50% of all diagnoses
• Muscle biopsy evidence: Perivascular inflammation
• Cutaneous involvement
• Electromyographic/Magnetic resonance imaging evidence of disease activity 

Management 

The mainstay management for dermatomyositis is with glucocorticoids. A dose of 1 – 1.5mg/kg/day of prednisolone is typically the initial treatment. Steroid sparing agents such as methotrexate may also be used.

In patients with a severe/refractory disease intravenous immunoglobulin is added.