What are the symptoms and treatment of juvenile dermatomyositis?

Juvenile Dermatomyositis: Symptoms and Treatment

Juvenile dermatomyositis (JDM) requires early aggressive treatment with high-dose corticosteroids (2 mg/kg/day up to 60 mg daily) combined with methotrexate (15 mg/m² weekly) as first-line therapy to prevent long-term complications and improve outcomes. 1

Clinical Presentation and Symptoms

Characteristic Skin Manifestations

• Pathognomonic skin findings:
  • Heliotrope rash (purplish discoloration of the eyelids)
  • Gottron papules (erythematous, scaly papules over knuckles)
  • Gottron sign (erythematous patches over extensor surfaces)
  • Periungual telangiectasias
  • Photosensitive rash with poikiloderma

Muscle Involvement

• Symmetric proximal muscle weakness (develops over weeks to months)
  • Primarily affects proximal muscles of upper and lower extremities
  • Neck flexors often weaker than extensors
  • Proximal leg muscles weaker than distal muscles
  • May lead to difficulty climbing stairs, rising from sitting position, or lifting arms

Other Clinical Manifestations

• Calcinosis cutis (more common in JDM than adult dermatomyositis)
• Cutaneous vasculitis and ulcerations
• Dysphagia or esophageal dysmotility
• Constitutional symptoms (fever, fatigue, weight loss)
• Nailfold capillary changes (detected by capillaroscopy)

Extramuscular Manifestations

• Gastrointestinal vasculopathy
• Interstitial lung disease (in approximately 8% of patients)
• Cardiac involvement (pericarditis, arrhythmias, systolic/diastolic dysfunction)
• Lipodystrophy
• Osteoporosis

Diagnostic Approach

Laboratory Evaluation

• Elevated muscle enzymes:
  • Creatine kinase (CK)
  • Lactate dehydrogenase (LDH)
  • Aspartate aminotransferase (AST)
  • Aldolase
• Inflammatory markers (ESR, CRP)
• Myositis-specific autoantibodies (anti-TIF1γ most common in JDM)

Imaging

• MRI with T2-weighted fat suppression techniques is preferred for detecting muscle inflammation 1
• Helps identify appropriate muscle biopsy site and monitor treatment response

Functional Assessment

• Childhood Myositis Assessment Scale (CMAS)
• Manual Muscle Testing (MMT)
• Pulmonary function tests to assess for lung involvement

Treatment Algorithm

Initial Treatment for Uncomplicated JDM

1. Corticosteroids:

   • Begin with prednisone 2 mg/kg/day (maximum 60 mg/day) 1
   • Taper after 2-4 weeks depending on clinical response

2. Concurrent Steroid-Sparing Agent:

   • Methotrexate 15 mg/m² subcutaneously once weekly 1

For Severe Disease

1. High-dose intravenous methylprednisolone plus one or more of:
   • Intravenous immunoglobulin (IVIG)
   • Cyclophosphamide (for major organ involvement/extensive ulcerative skin disease)
   • Rituximab (for refractory disease, noting it may take up to 26 weeks to work)
   • Cyclosporine 1

For Methotrexate Intolerance

• Switch to alternative DMARDs:
  • Cyclosporine A
  • Mycophenolate mofetil 1

For Refractory Disease

• Anti-TNF therapies (infliximab or adalimumab preferred over etanercept) 1
• Intensify immunosuppressive therapy if calcinosis develops 1

Adjunctive Skin-Directed Therapy

• Topical tacrolimus (0.1%) or topical steroids for localized skin disease, particularly for symptomatic redness or itching 1
• Sun protection and photoprotection

Treatment Duration and Monitoring

• Regular assessment of disease activity using validated tools:

  • Muscle strength (CMAS, MMT)
  • Cutaneous assessment tools (CAT)
  • Nailfold capillaroscopy

• Consider treatment withdrawal if:

  • Patient has been off steroids and in remission on methotrexate for minimum of 1 year 1

Important Considerations and Pitfalls

1. Early diagnosis and aggressive treatment are crucial for preventing long-term complications such as calcinosis, which typically develops 1-3 years after onset of muscle weakness 2

2. Multidisciplinary care is essential, involving rheumatology, dermatology, and physical therapy. Notably, dermatology is often underutilized despite the characteristic skin findings 3

3. Beware of atypical presentations - some patients may present with skin manifestations months or years before muscle weakness develops 4

4. Monitor for steroid-related complications including hypertension, growth delay, and osteoporosis 1

5. Pulmonary assessment is important even in asymptomatic patients, as ILD can be clinically silent but contribute to morbidity and mortality 1