What is the treatment for inclusion body myositis?

Treatment for Inclusion Body Myositis

Currently, there is no known effective treatment for reversing or minimizing the progression of inclusion body myositis (IBM). 1 Despite various treatment attempts targeting both inflammatory and atrophic features of this condition, no therapy has been proven to halt disease progression.

Disease Characteristics

IBM is characterized by:

• Symmetric or asymmetric weakness of insidious onset affecting proximal and/or distal muscles
• Typically occurs after age 50 years with a male to female ratio of 3:1
• Classic atrophy of forearm flexors, finger flexors, and quadriceps muscles
• Dysphagia may be a prominent feature leading to poor outcomes
• Minimally elevated muscle enzyme levels (CK)
• Muscle biopsy showing inflammatory mononuclear cell infiltrate with rimmed vacuoles and congophilic deposits 2

Evidence on Treatment Options

Immunosuppressive Therapies

• Corticosteroids: Not effective for IBM, unlike other inflammatory myopathies 2, 3
• Methotrexate (MTX): Moderate-quality evidence shows MTX does not arrest or slow disease progression 1
• Interferon beta-1a: Moderate-quality evidence indicates no important difference compared to placebo 1
• Intravenous Immunoglobulin (IVIG): Insufficient evidence to support efficacy 1
• Azathioprine with MTX: Inconclusive evidence 1

Other Approaches

• Anti-T lymphocyte immunoglobulin (ATG) with MTX: Very low-quality evidence suggesting potential benefit compared to MTX alone 1
• Oxandrolone: Inconclusive evidence 1
• Arimoclomol: Complete analysis pending data publication 1
• Bimagrumab: Studies ongoing 1

Management Approach

Given the lack of disease-modifying treatments, management should focus on:

1. Multidisciplinary Care:

   • Include physiotherapist and specialist nurse 3
   • Implement individualized and supervised exercise programs to improve muscle performance 3

2. Symptomatic Management:

   • Pain control with acetaminophen or NSAIDs if no contraindications 3
   • For severe pain/spasms, consider stronger interventions under medical supervision 3

3. Monitoring:

   • Regular assessment of muscle strength
   • Serial creatine kinase (CK) measurements
   • Functional status evaluation
   • Annual assessment of disease damage using validated indices 3

4. Complication Prevention:

   • Monitor for dysphagia and consider interventions to prevent aspiration pneumonia 2
   • Assess for cardiac complications including arrhythmias 3
   • Monitor for respiratory complications 3

Important Considerations

• IBM is distinct from other inflammatory myopathies in its poor response to immunosuppressive therapies
• Clinical trials have been limited by small sample sizes, short duration, and heterogeneous outcome measures 1
• The pathogenesis remains unclear, with debates about whether it's primarily an autoimmune inflammatory myopathy or a degenerative myopathy with secondary inflammation 4
• Early diagnosis is important for appropriate management expectations and to avoid prolonged ineffective immunosuppressive treatments

Future Directions

More research is needed, including:

• Larger, longer-duration randomized controlled trials
• Standardized and responsive outcome measures
• Further investigation into the pathophysiological mechanisms to identify new therapeutic targets 5, 6

While awaiting more effective treatments, management should focus on maintaining function through appropriate exercise and addressing complications to optimize quality of life.