Treatment of Viral Myositis in Children
Viral myositis in children is a benign, self-limited condition that requires only supportive care with rest, hydration, and analgesics—no immunosuppressive therapy or antivirals are needed in uncomplicated cases. 1, 2
Distinguishing Viral Myositis from Conditions Requiring Aggressive Treatment
Before initiating treatment, it is critical to confirm you are dealing with true viral myositis and not a condition requiring urgent intervention:
Viral myositis presents with bilateral lower extremity pain, refusal to walk or tiptoe gait, recent viral illness (typically influenza A or B), normal or mildly elevated CPK (<10x normal, typically 1000-3000 U/L), no rash, and preserved muscle strength (pain-related limitation only, not true weakness). 1, 3, 2
Rule out immune-mediated necrotizing myopathy, which requires high-dose corticosteroids plus steroid-sparing agents and presents with markedly elevated CPK (>10x normal), true muscle weakness, and subacute onset. 1
Rule out infectious necrotizing myositis, which requires immediate surgical debridement and broad-spectrum antibiotics (mortality 36.5% even with treatment) and presents with severe systemic toxicity, asymmetric involvement, and rapid progression. 1
Rule out juvenile dermatomyositis, which requires immunosuppression with corticosteroids and methotrexate and presents with characteristic rash (heliotrope, Gottron papules), proximal muscle weakness, and elevated muscle enzymes. 4
Supportive Management Protocol
For confirmed viral myositis, implement the following supportive measures:
Pain management: Acetaminophen or NSAIDs for myalgias and calf pain (no contraindications in viral myositis). 1
Hydration: Ensure adequate fluid intake, particularly if CPK is elevated, to prevent potential renal complications from myoglobinuria. 5, 3, 6
Rest: Activity restriction until symptoms resolve, typically 3-7 days. 2
Fever management: Antipyretics as needed for comfort. 5
When to Consider Antiviral Therapy
Oseltamivir may be considered if the child presents within 48 hours of influenza symptom onset, though viral myositis itself does not require antiviral treatment. 6 The decision should be based on influenza treatment guidelines, not the presence of myositis.
Monitoring and Follow-Up
Most cases resolve within 3-7 days without complications:
CPK typically normalizes within 7 days (median time to normalization). 3
Clinical symptoms (pain, walking difficulty) usually resolve within 3 days. 2
No routine laboratory monitoring is needed for uncomplicated cases seen in the outpatient setting. 2
Indications for Hospital Admission
Consider admission for:
Severe CPK elevation (≥5000 U/L) with risk of rhabdomyolysis and acute kidney injury. 3
Myoglobinuria detected on urinalysis. 2
Dehydration requiring intravenous fluids. 6
Inability to ambulate with inadequate home support. 5
Recurrent episodes warranting screening for underlying metabolic or muscular disorders. 3
Critical Pitfalls to Avoid
Do not initiate corticosteroids or immunosuppressive therapy for viral myositis, as this is a self-limited condition that does not benefit from immunomodulation and such treatment could be harmful. 1, 2 Corticosteroids are only indicated for inflammatory myopathies (juvenile dermatomyositis, immune-mediated necrotizing myopathy), not viral myositis.
Do not perform extensive investigations (muscle biopsy, EMG, autoantibody panels) in typical presentations, as this increases cost, patient anxiety, and delays appropriate supportive care. 5, 3
Reassure parents that this condition is benign and self-resolving, as the dramatic presentation (refusal to walk) often causes significant parental anxiety despite the excellent prognosis. 5, 7
Special Considerations
Emerging viral associations: While influenza A and B remain the most common causes, SARS-CoV-2 has been identified as a new potential trigger for viral myositis. 3 The clinical presentation and management remain identical regardless of the viral etiology.
Asymmetric weakness or true muscle weakness (not just pain-related limitation) indicates inflammatory myopathy rather than viral myositis and requires urgent evaluation and consideration of immunosuppressive therapy. 1
Presence of rash indicates dermatomyositis requiring immunosuppression with corticosteroids (2 mg/kg/day up to 60 mg daily) plus subcutaneous methotrexate (15 mg/m² weekly), not viral myositis. 4