Corticosteroids in Viral Myositis: Why They Are Contraindicated
Corticosteroids should not be given to a teenager with viral myositis because they suppress immune function and can exacerbate viral infections, increase the risk of disseminated infection, and mask signs of ongoing infection—all while the condition is self-limited and resolves without immunosuppressive therapy. 1
Key Distinction: Viral vs. Autoimmune Myositis
The critical issue here is distinguishing viral myositis from idiopathic inflammatory myopathies (IIM) such as dermatomyositis or polymyositis:
- Viral myositis (benign acute childhood myositis) is a self-limited syndrome associated with viral infections, most commonly influenza, that resolves spontaneously without immunosuppressive treatment 2
- Idiopathic inflammatory myopathies are autoimmune conditions where corticosteroids are the mainstay of therapy 3, 4, 5
Why Corticosteroids Are Harmful in Viral Myositis
Immunosuppression Risks
Corticosteroids fundamentally suppress the immune system, which creates multiple dangers in active viral infection 1:
- Reduce resistance to infections and allow viral replication to continue unchecked 1
- Exacerbate existing infections by impairing the body's natural antiviral response 1
- Increase risk of disseminated infections as the virus spreads beyond the initial site 1
- Mask signs of infection, making it difficult to monitor disease progression 1
Evidence from Viral Myocarditis
The Cochrane review on corticosteroids for viral myocarditis (a related viral muscle condition) found that corticosteroids do not reduce mortality and the evidence for any benefit is of low quality 6. This reinforces that immunosuppression during active viral infection provides no mortality benefit and carries theoretical harm 6.
Natural Course of Viral Myositis
Benign acute childhood myositis has an excellent prognosis without immunosuppression 2:
- All patients in a large series had normal neurological examinations 2
- No patients developed myoglobinuria or renal failure 2
- No patients had residual muscular impairment 2
- The condition is self-limited, typically resolving within days with supportive care only 2
Appropriate Management of Viral Myositis
The correct approach for a teenager with viral myositis includes 2:
- Hydration to prevent complications from elevated creatine kinase 2
- Rest to allow muscle recovery 2
- Analgesics (NSAIDs or acetaminophen) for pain control 2
- Careful follow-up to monitor CK levels and ensure resolution 2
- No immunosuppression is indicated 2
Critical Pitfall to Avoid
The major clinical error is misdiagnosing viral myositis as an autoimmune inflammatory myopathy and initiating corticosteroids inappropriately. Key distinguishing features 3, 2:
- Viral myositis: Acute onset, recent viral illness (especially influenza), symmetric lower extremity pain, self-limited course, affects school-aged children 2
- Autoimmune myositis: Subacute to chronic onset, proximal muscle weakness (not just pain), elevated muscle enzymes persisting beyond acute viral illness, may have extramuscular manifestations like rash (dermatomyositis) or interstitial lung disease 3, 7
When Corticosteroids ARE Indicated
Corticosteroids are the cornerstone of treatment only for autoimmune inflammatory myopathies 3, 4, 5:
- High-dose corticosteroids (1-2 mg/kg/day prednisone) are initiated for idiopathic inflammatory myopathies like dermatomyositis, polymyositis, or immune-mediated necrotizing myopathy 3
- For juvenile dermatomyositis specifically, prednisone 2 mg/kg up to 60 mg/day is recommended 3
- These are autoimmune conditions, not viral infections, where immune suppression targets pathologic autoimmunity rather than impairing antiviral defense 3, 4
Corticosteroid Dosing Threshold for Immunosuppression
The FDA label specifies that prednisone ≥20 mg/day for ≥14 days causes sufficient immunosuppression to raise serious concerns about infection risk 3, 1. Even at lower doses during active viral infection, the risk-benefit ratio favors avoiding corticosteroids entirely when the underlying condition is self-limited 1, 2.