From the Guidelines
Elevated Creatine Phosphokinase (CPK) levels after influenza in pediatric patients are often caused by viral myositis, a temporary inflammation of muscle tissue, and usually resolve on their own with monitoring and supportive care. Key points:
- No specific treatment is usually required for mildly elevated CPK post-flu, as stated in the general guidelines for managing influenza complications 1.
- Ensure adequate hydration with oral fluids or IV if necessary, to prevent dehydration and potential kidney damage.
- Monitor CPK levels every 2-3 days until they return to normal, to assess the resolution of muscle inflammation.
- Advise rest and avoiding strenuous physical activity until CPK normalizes, to prevent further muscle damage. If CPK levels are significantly elevated (>5000 U/L) or accompanied by muscle pain, weakness, or dark urine:
- Consider hospital admission for IV hydration and close monitoring, as recommended for severe cases of influenza and its complications 1.
- Check renal function and urine myoglobin, to rule out rhabdomyolysis and potential kidney damage.
- Consult pediatric neurology or rheumatology if levels remain persistently high, to investigate underlying conditions that may be contributing to elevated CPK levels. Justification: Elevated CPK post-flu is often due to viral myositis, a temporary inflammation of muscle tissue, which can be caused by the flu virus directly damaging muscle fibers, leading to CPK release 1. Most cases are self-limiting, but monitoring is important to rule out more serious conditions like rhabdomyolysis, which can lead to kidney damage if severe and untreated. The provided evidence does not directly address the cause of elevated CPK after influenza in pediatric patients, but general guidelines for managing influenza complications and supportive care can be applied to this scenario 1.
From the Research
Causes of Elevated Creatine Phosphokinase (CPK) after Influenza in Pediatric Patients
- Elevated CPK levels in pediatric patients after influenza infection can be attributed to influenza-associated myositis (IAM), a rare and poorly recognized complication of influenza virus infection in children 2, 3, 4.
- IAM typically occurs in school-aged children, with a 2:1 male predominance, and is characterized by acute onset of severe pain in the lower extremities and a refusal to ambulate walk 2, 4.
- The calf muscles are often involved, alone or together with other muscle groups, and blood CPK concentration is invariably elevated 2, 4.
- Influenza B and A viruses have been identified in IAM cases, with influenza B being more common in some studies 2, 4.
- Elevated CPK levels have also been reported in patients with influenza A infection, with muscle biopsies showing focal necrosis and myopathic changes 5.
- The involvement of skeletal muscle in influenza infection may contribute to elevated CPK levels, which can be a useful diagnostic marker for IAM 5, 6.
- The clinical and laboratory findings of IAM are highly characteristic and allow for rapid diagnosis during the influenza season, with supportive measures and early diagnosis being crucial in managing children with viral myositis 2, 3, 4.