What is the treatment for orbital myositis?

Treatment of Orbital Myositis

High-dose systemic corticosteroids are the first-line treatment for orbital myositis, with immunosuppressive agents recommended for recurrent or steroid-dependent cases. 1

Diagnostic Evaluation

Before initiating treatment, confirm the diagnosis with:

• Complete ophthalmologic examination assessing:

  • Orbital and periorbital pain
  • Restricted eye movements
  • Diplopia
  • Proptosis
  • Eyelid swelling
  • Conjunctival hyperemia

• Laboratory testing:

  • CK, AST, ALT, LDH levels
  • Inflammatory markers (ESR, CRP)
  • Myositis-associated antibodies
  • Thyroid function tests (to rule out thyroid eye disease)

• Imaging:

  • MRI of orbits (preferred) showing enlarged extraocular muscles
  • CT scan as alternative
  • Ultrasound may be helpful

Treatment Algorithm

Acute Phase Treatment

1. First-line: Systemic Corticosteroids

   • Prednisone 0.5-1 mg/kg/day (typically 40-60 mg daily) 1
   • For severe cases with bulbar symptoms or significant inflammation:
     • IV methylprednisolone 1-2 mg/kg/day or higher dose bolus 1

2. Response Assessment

   • Most patients respond within days to corticosteroids 1
   • Continue initial dose until clinical improvement (typically 1-2 weeks)
   • Then gradually taper over 4-6 weeks

For Recurrent or Steroid-Dependent Cases

Factors associated with recurrence include 2:

• Male gender
• Multiple or bilateral extraocular muscle involvement
• Horizontal muscle involvement
• Lack of proptosis
• Poor response to initial steroid treatment

Treatment options:

1. Steroid-Sparing Immunosuppressants 1, 3

   • Methotrexate: Start at 15 mg weekly, increase to target 25 mg weekly
   • Azathioprine: Start at 25-50 mg/day, target 2 mg/kg
   • Mycophenolate mofetil: Start at 500 mg twice daily, increase to 1000 mg twice daily

2. Biological Agents 1

   • For refractory cases:
     • Rituximab (anti-CD20)
     • TNF-α inhibitors (if associated fasciitis)
     • IL-6 receptor antagonists

3. Intravenous Immunoglobulin (IVIG) 3, 4

   • Dosage: 1-2 g/kg divided over 1-2 days
   • Repeat monthly for 1-6 months
   • Particularly effective for recurrent cases
   • Check serum IgA levels before administration

4. Plasmapheresis 1

   • Consider for severe or acute disease
   • Particularly if poor response to other therapies
   • Note: Should not be performed immediately after IVIG

Monitoring and Follow-up

• Regular assessment of:

  • Muscle strength and eye movements
  • Visual acuity
  • Inflammatory markers
  • Side effects of medications

• Frequency of follow-up:

  • Every 1-2 weeks during acute phase
  • Every 1-3 months during maintenance therapy

Important Considerations

• Radiotherapy (20 Gy) has been used historically but appears ineffective in preventing recurrences 5
• NSAIDs alone may be sufficient for very mild cases but are generally inadequate for moderate to severe disease 1, 2
• Chronic or recurrent orbital myositis may require long-term immunosuppression 6, 7
• Monitor for potential complications of long-term corticosteroid or immunosuppressant use

Prognosis

Over 80% of patients experience favorable clinical outcomes with appropriate treatment, though recurrence rates can be as high as 50-56% 1, 5. Early aggressive treatment in patients with risk factors for recurrence may improve long-term outcomes.