From the Guidelines
Post viral myositis should be managed based on the severity of symptoms, with mild cases (G1) involving continuation of immune checkpoint inhibitors (ICPi) and oral corticosteroids if necessary, while moderate to severe cases (G2-4) require temporary or permanent discontinuation of ICPi and initiation of corticosteroids, with potential addition of other immunosuppressants or therapies as needed. The management of post viral myositis involves a step-wise approach, considering the grade of symptoms and the presence of elevated creatine kinase (CK) levels or other complications. For G1 symptoms, which include mild weakness with or without pain, the recommendation is to continue ICPi and consider oral corticosteroids starting at 0.5 mg/kg/day if CK and/or aldolase are elevated and the patient has muscle weakness, along with analgesia using acetaminophen or NSAIDs for myalgia if there are no contraindications 1.
Management by Symptom Severity
- For G2 symptoms, which involve moderate weakness with or without pain limiting age-appropriate instrumental activities of daily living (ADL), the approach is to hold ICPi temporarily and may resume upon symptom control, with the initiation of prednisone or equivalent at 0.5-1 mg/kg/day, and consideration of NSAIDs as needed, along with referral to a rheumatologist or neurologist 1.
- For G3-4 symptoms, characterized by severe weakness with or without pain limiting self-care ADL, the recommendation is to hold ICPi, consider hospitalization for severe cases, and initiate prednisone 1 mg/kg/day or equivalent, with potential use of high-dose corticosteroids, IVIG, and other immunosuppressants in severe or refractory cases 1.
Diagnostic Evaluation and Treatment
Diagnostic evaluation should include myositis-associated autoantibodies, MRI, and electromyogram (EMG) biopsy, with fasciitis frequently reported on MRI 1. The treatment approach is tailored to the severity of symptoms and the presence of complications, with the goal of eliminating organ inflammation, preventing disease complications, and restoring quality of life. High-dose corticosteroids are often initiated at diagnosis for severe cases, with the potential addition of steroid-sparing agents, and other therapies such as IVIG, plasma exchange, or selective separation for refractory cases or those with severe compromise 1.
Key Considerations
- The management of post viral myositis requires careful consideration of the severity of symptoms, the presence of elevated CK levels, and the potential for complications such as rhabdomyolysis or myocarditis.
- The use of corticosteroids and other immunosuppressants should be tailored to the individual patient's needs, with careful monitoring for response and potential side effects.
- Referral to a rheumatologist or neurologist is recommended for patients with moderate to severe symptoms or those who do not respond to initial treatment.
From the Research
Definition and Causes of Post-Viral Myositis
- Post-viral myositis refers to inflammation of the muscles that occurs after a viral infection 2.
- It can be triggered by various viruses, including influenza A/B, enteroviruses, and other viruses 2.
- The condition may lead to severe complications, such as rhabdomyolysis, which is the breakdown of muscle tissue 2.
Clinical Presentation and Diagnosis
- Patients with post-viral myositis may experience muscle weakness, pain, and inflammation [(3,4)].
- Laboratory tests may reveal elevated creatine kinase levels, indicating muscle damage 2.
- Muscle MRI and biopsy may also be used to diagnose the condition 5.
Treatment and Management
- Glucocorticoids are considered the mainstay of treatment for myositis, including post-viral myositis 4.
- Some patients may require add-on immunosuppressive therapy due to insufficient response to glucocorticoids or relapses 4.
- Non-steroidal anti-inflammatory drugs (NSAIDs) may not be effective in managing post-viral myositis, and their use should be cautious 6.
- Corticosteroids have been shown to be effective in treating post-infection myositis, with most patients having favorable prognoses 5.