What is the treatment for body myositis?

Treatment for Body Myositis

For body myositis (inclusion body myositis), the recommended treatment includes a trial of prednisone combined with methotrexate, though treatment response is generally poor and there is no established therapy that significantly improves, arrests, or slows disease progression. 1, 2

Diagnostic Evaluation

Before initiating treatment, a thorough diagnostic evaluation should include:

• Assessment of muscle strength using validated measures (MMT8)
• Laboratory tests:
  • Muscle enzymes (CK, LDH, AST, ALT, aldolase)
  • Inflammatory markers (ESR, CRP)
  • Myositis-specific and myositis-associated autoantibodies
  • Troponin (to evaluate myocardial involvement)
• Imaging: MRI of affected muscles using T2-weighted/STIR sequences
• Consider EMG and muscle biopsy (especially important for inclusion body myositis diagnosis)
• Systemic evaluation including pulmonary function tests and cardiac testing

Treatment Approach for Body Myositis

First-Line Treatment

• Trial of oral prednisone (0.5-1 mg/kg/day) combined with methotrexate 1, 2
• This approach is warranted in selected patients, though response is typically limited

Treatment for Different Types of Inflammatory Myopathies

1. Inclusion Body Myositis (IBM):

   • Limited response to immunosuppressive therapy
   • Trial of prednisone with methotrexate may be attempted in selected patients
   • No established treatment has been proven to improve, arrest, or slow progression 2

2. Dermatomyositis and Polymyositis:

   • High-dose corticosteroids (prednisone 0.5-1 mg/kg/day) combined with immunosuppressive agents:
     • Methotrexate (preferred first-line steroid-sparing agent)
     • Azathioprine (alternative)
     • Mycophenolate mofetil 3, 1, 4

3. Necrotizing Autoimmune Myopathy:

   • High-dose corticosteroids combined with immunosuppressive agents 1

Management of Refractory Cases

For patients with inadequate response to initial therapy:

1. Consider IVIG therapy (particularly effective for dermatomyositis) 3, 4
2. Consider rituximab for refractory cases 3, 4
3. Other options for resistant cases:
   • Mycophenolate mofetil
   • Tacrolimus
   • Cyclosporine 3, 4, 5
4. For severe cases with significant weakness:
   • Consider hospitalization
   • IV methylprednisolone (1-2 mg/kg) or higher-dose bolus for severe compromise 3
   • Consider plasmapheresis in selected cases 3

Supportive Care

• Physical therapy and appropriate exercise program monitored by a physiotherapist 1
• Symptomatic management of pain with acetaminophen or NSAIDs if no contraindications 3

Monitoring and Follow-up

• Regular assessment of muscle strength and enzymes (CK, ESR, CRP)
• Monitor for treatment-related adverse effects:
  • Steroid-related myopathy
  • Osteoporosis
  • Infections
• Annual assessment of disease damage using validated indices
• Cardiac evaluation for patients at high risk

Important Caveats

1. Treatment Expectations for IBM: Unlike other inflammatory myopathies, inclusion body myositis typically responds poorly to immunosuppressive therapy. High-dose prednisone may actually worsen strength while decreasing inflammation but increasing amyloid accumulation 2.

2. Early Intervention: Early initiation of therapy is associated with better functional outcomes in inflammatory myopathies, though this benefit is less clear in inclusion body myositis 6.

3. Steroid-Sparing Approach: Most patients require early introduction of steroid-sparing agents to facilitate tapering of prednisone and minimize adverse effects 4, 6.

4. Treatment Duration: The optimal duration of therapy remains unclear, and long-term management often requires balancing disease control with medication side effects 6.

5. Novel Approaches: For inclusion body myositis specifically, alternative targets for intervention and novel treatment strategies are needed as conventional immunosuppression has limited efficacy 2.

In summary, while treatment options for inflammatory myopathies like dermatomyositis and polymyositis are relatively well-established, inclusion body myositis remains challenging with limited therapeutic options and poor response to conventional immunosuppression.