What is the treatment for dermatomyositis?

Treatment of Dermatomyositis

The recommended first-line treatment for dermatomyositis is high-dose corticosteroids (oral or intravenous) combined with methotrexate. 1

Diagnostic Evaluation Before Treatment

Before initiating treatment, a thorough diagnostic evaluation should include:

• Muscle assessment:

  • Muscle strength and function testing using validated measures like MMT8 and CMAS 1
  • Muscle enzymes (CPK, LDH, AST, ALT, aldolase) 1, 2
  • MRI of muscles using T2-weighted/STIR sequences to detect inflammation 1
  • Muscle biopsy (especially in atypical presentations without rash) 1

• Skin assessment:

  • Formal Cutaneous Assessment Tool (CAT) 1
  • Nailfold capillaroscopy 1

• Systemic evaluation:

  • Pulmonary function tests with CO diffusion capacity 1
  • Echocardiography and ECG 1
  • Screening for calcinosis 1
  • Autoantibody testing (myositis-specific and myositis-associated antibodies) 1, 2

Treatment Algorithm

First-line Treatment

1. Corticosteroids:

   • Initial high-dose prednisone: 0.5-1 mg/kg/day for adults 2
   • For juvenile dermatomyositis: 2 mg/kg/day up to 60 mg/day 2
   • Gradual taper after 2-4 weeks based on clinical response 2

2. Methotrexate:

   • Start concurrently with corticosteroids 1
   • Helps as a steroid-sparing agent

3. Supportive measures:

   • Sun protection and routine use of sunblock 1
   • Safe and appropriate exercise program monitored by a physiotherapist 1
   • Multidisciplinary team approach including physiotherapist and specialist nurse 1

Second-line/Refractory Disease Treatment

For patients with inadequate response to first-line therapy:

1. Other Disease-Modifying Antirheumatic Drugs (DMARDs):

   • Azathioprine 2
   • Mycophenolate mofetil 2
   • Cyclosporine 2
   • Leflunomide 1

2. Intravenous Immunoglobulin (IVIG):

   • Recommended dose: 1-2 g/kg for 1-6 months 2
   • Particularly useful for refractory cases

3. Biologic agents:

   • Rituximab for severe, refractory cases or patients with interstitial lung disease 2
   • Consider TNF-α or IL-6 antagonists in selected cases 1

Special Considerations

Juvenile Dermatomyositis

• Presents in patients under 18 years with similar skin and muscle features as adult DM 1
• May have additional manifestations including Raynaud phenomenon, inflammatory arthritis, pneumonitis, vasculopathy of the gastrointestinal tract, and cardiomyopathy 1
• Can be classified based on disease course: monocyclic, polycyclic, chronic, and ulcerative disease 1
• Watch for macrophage activation syndrome, a severe life-threatening complication 1

Amyopathic and Hypomyopathic Dermatomyositis

• Amyopathic DM: Classic rash without evidence of muscle inflammation 1
• Hypomyopathic DM: No muscle weakness but evidence of muscle inflammation 1
• Both forms may have interstitial lung disease and associated malignancy 1
• Treatment should focus on skin manifestations and monitoring for systemic complications

Monitoring and Follow-up

• Regular assessment of muscle strength and enzymes to monitor disease activity 2
• Use of standardized tools like Disease Activity Score for ongoing assessment 1
• Annual assessment of disease damage using Myositis Damage Index 1
• Cardiac evaluation for patients at high risk (hypertension, high disease activity 1 year post-diagnosis, long-term high corticosteroid burden, chronic ongoing active disease) 1
• Monitoring for calcinosis, a common complication occurring on average 2.9 years after disease onset 1

Common Pitfalls and Caveats

• Delayed diagnosis: Early recognition is critical to avoid erosive joint damage and other complications 1
• Inadequate steroid tapering: Consider starting steroid-sparing agents earlier than with other conditions 1
• Overlooking associated conditions: Screen for interstitial lung disease and malignancy 1
• Neglecting skin care: Sun protection is essential to prevent skin flares 1
• Insufficient monitoring: Regular assessment of muscle strength, enzymes, and potential complications is necessary 2
• Overlooking swallowing function: Formal assessment of swallow function should be performed in every patient 1

By following this comprehensive approach to the treatment of dermatomyositis, clinicians can effectively manage both the cutaneous and muscular manifestations of the disease while monitoring for potential complications.