What is the initial management of fever in patients with polymyositis?

Initial Management of Fever in Patients with Polymyositis

For patients with polymyositis presenting with fever, high-dose corticosteroids (prednisone 2 mg/kg/day up to 60 mg/day) should be initiated as first-line treatment, with consideration of bolus administration in severe cases. 1

Diagnostic Evaluation

Before initiating treatment, a thorough evaluation should be performed to identify the cause of fever:

1. Rule out infections:

   • Complete blood count (CBC)
   • Blood cultures
   • Urinalysis and urine culture
   • Chest radiography to rule out pneumonia (especially aspiration pneumonia, which is a common complication in polymyositis) 2

2. Assess disease activity:

   • Muscle enzymes (CK, LDH, AST)
   • Inflammatory markers (ESR, CRP)
   • Myositis-specific antibodies 1

3. Consider alternative causes:

   • Medications
   • Malignancy (polymyositis can be associated with malignancies) 3
   • Other systemic autoimmune diseases 3

Treatment Algorithm

Step 1: Determine if fever is due to disease flare or infection

• If clinical and laboratory evidence suggests active polymyositis (elevated muscle enzymes, worsening weakness):

  • Initiate high-dose corticosteroids (prednisone 2 mg/kg/day up to 60 mg/day) 1
  • In severe cases with significant inflammation, consider IV pulse methylprednisolone 4

• If evidence suggests infection:

  • Initiate appropriate antimicrobial therapy based on suspected source
  • Hold immunosuppressive medications temporarily if infection is severe
  • Resume immunosuppression once infection is controlled

Step 2: For disease flare with fever

• Monitor response to corticosteroids within 2-4 weeks 1
• If inadequate response:
  • Add steroid-sparing agent (methotrexate 15-25 mg weekly is preferred) 1
  • Consider azathioprine or mycophenolate mofetil as alternatives, especially if there is concern for interstitial lung disease with methotrexate 1, 5

Step 3: For refractory cases

• Consider IVIG (1 g/kg divided over 1-2 days, repeated monthly) 1
• For severe cases, intensive combined therapy with high-dose glucocorticoids, tacrolimus, and IVIG may be necessary 1
• Rituximab may be effective in approximately 62% of patients with refractory disease 1

Special Considerations

• Pulmonary involvement: Patients with polymyositis are at risk for interstitial lung disease, aspiration pneumonia, and hypoventilation, which can present with fever 2

  • Perform high-resolution CT and pulmonary function tests if respiratory symptoms are present

• Cardiac involvement: Cardiac muscle inflammation can lead to arrhythmias and heart failure, which may present with fever 3

  • Consider ECG and echocardiogram in the evaluation

• Dysphagia: Weakness of upper esophageal muscles can lead to aspiration pneumonia 3

  • Evaluate swallowing function if aspiration is suspected

Monitoring

• Regular assessment of muscle strength and CK levels, with target CK levels in the low-normal range 1
• Monitor for treatment-related complications, particularly with long-term corticosteroid use
• Assess functional status improvement and ability to taper corticosteroids 1

Common Pitfalls

• Failure to distinguish between infection and disease flare: Both can present with fever and elevated inflammatory markers. Careful evaluation is essential before escalating immunosuppression.

• Overlooking aspiration pneumonia: Patients with polymyositis may have subtle dysphagia leading to aspiration, which can cause fever and respiratory symptoms 2, 3

• Inadequate initial corticosteroid dosing: Underdosing may lead to persistent inflammation and fever. High-dose therapy is recommended initially with subsequent tapering based on response 1

• Neglecting to screen for malignancy: Polymyositis can be associated with underlying malignancies that may contribute to systemic symptoms including fever 3