Dermatomyositis (DM) is a rare, chronic autoimmune disease that systemically affects the skin and skeletal muscles. It can occur in both juvenile and adult forms and is characterized by a combination of muscle weakness and distinctive skin rashes. In adults, especially older individuals, DM is sometimes associated with underlying malignancies or interstitial lung disease (1).

Symptoms

The most common symptom is symmetrical proximal muscle weakness, making activities such as climbing stairs, rising from a chair, or lifting arms overhead difficult (1).

Skin signs often appear early and may include:

• Heliotrope rash (purple discoloration around the eyes)
• Gottron’s papules (scaly red or violet bumps on the knuckles)
• Shawl sign (rash on the upper back and shoulders)
• Photosensitive rashes on the chest and upper limbs (2)

Causes

The exact cause of dermatomyositis remains unknown, but it is believed to involve:

• Autoimmune mechanisms, where the immune system attacks its own tissues
• Genetic predisposition
• Environmental triggers, such as infections or drug reactions
• In adults, it may occur paraneoplastically (as a response to an underlying tumor) (2)

Risk Factors

• Age: More common in adults aged 40–60 and children aged 5–15
• Gender: Higher prevalence in females
• Genetic susceptibility
• Presence of other autoimmune disorders
• Cancer, particularly in newly diagnosed adult cases (2)

Diagnosis

Diagnosis is based on a combination of clinical signs, lab results, and imaging/biopsy findings:

• Blood tests showing elevated CK, LDH, and aldolase
• Positive ANA and myositis-specific antibodies like anti-Mi-2 or anti-MDA5
• EMG, MRI, or biopsy showing perifascicular atrophy and perivascular inflammation
• Skin biopsy may also support the diagnosis
• Cancer screening is essential in adults due to the risk of malignancy-associated DM (3)

Treatment Options

• Corticosteroids
• Immunosuppressants such as methotrexate or azathioprine
• Biologic agents like rituximab
• IVIG for severe or resistant cases
• Physical therapy is important to preserve muscle strength
• Treating any associated malignancy can improve outcomes in paraneoplastic cases (3)

Living With Dermatomyositis / Prevention

Although DM is a chronic illness, many patients can achieve remission or maintain long-term disease control with timely treatment.

Lifestyle strategies include:

• Regular follow-ups and lab monitoring
• Sun protection to prevent rash flare-ups
• Staying physically active through guided physiotherapy
• Emotional support or counseling to manage chronic fatigue or mood effects

There is currently no known prevention for DM, but early detection and management are key to reducing complications (3).

Reference

1. Dalakas, M.C. (2006). Inflammatory Muscle Diseases. New England Journal of Medicine.

2. Lundberg, I.E., et al. (2016). 2017 EULAR/ACR Classification Criteria for Idiopathic Inflammatory Myopathies. Annals of the Rheumatic Diseases.

3. Rider, L.G., & Miller, F.W. (2011). Deciphering the clinical spectrum of adult and juvenile dermatomyositis. Current Opinion in Rheumatology.