What are the treatment options for Myositis (inflammation of the muscles)?

From the Guidelines

Myositis treatment should be tailored to the specific type and severity of the condition, with corticosteroids like prednisone being the first-line treatment, and immunosuppressants and other therapies added as needed based on clinical response and severity. The treatment approach for myositis is guided by the severity of the condition, which can range from mild to severe, and is often classified based on grading such as G1, G2, G3-4, as outlined in the management guidelines 1. For mild cases (G1), treatment may involve continuing immune checkpoint inhibitor (ICPi) therapy, with the option to add oral corticosteroids like prednisone at a dose of 0.5 mg/kg/day, along with analgesia for myalgia and consideration of holding statins 1. In moderate cases (G2), temporary holding of ICPi, referral to a rheumatologist or neurologist, and initiation of prednisone or equivalent at 0.5-1 mg/kg/d may be necessary, with the possibility of permanent discontinuation of ICPi in cases with severe muscle involvement 1. For severe cases (G3-4), immediate action is required, including holding ICPi, considering hospitalization, urgent referral to specialists, and initiating high-dose prednisone or equivalent, with options for plasmapheresis, IVIG therapy, and other immunosuppressant therapies like rituximab, methotrexate, azathioprine, or mycophenolate mofetil 1. Regular monitoring of muscle enzymes, muscle strength, and medication side effects is crucial, and physical therapy plays a significant role in maintaining muscle strength and preventing contractures throughout treatment 1. Given the potential for severe complications, including myocarditis, and the importance of early recognition and management, a high index of suspicion for myositis is necessary, especially in patients treated with immune checkpoint inhibitors, with prompt initiation of appropriate therapy to improve outcomes 1.

From the FDA Drug Label

1. Collagen Diseases During an exacerbation or as maintenance therapy in selected cases of: Systemic lupus erythematosus Systemic dermatomyositis (polymyositis)

• Myositis treatment: The drug label indicates that prednisone is used in the treatment of Systemic dermatomyositis (polymyositis), which is a type of myositis.
• The use of prednisone for myositis treatment is specifically mentioned as an adjunctive therapy for short-term administration or as maintenance therapy in selected cases. 2

From the Research

Myositis Treatment Overview

• Myositis, or idiopathic inflammatory myopathy, is a group of autoimmune diseases with broad-spectrum clinical presentations, commonly presenting with muscle weakness and inflammation 3.
• The management of myositis presents significant challenges due to the rarity and variability of the disease and lack of large-scale, randomised controlled trials 3.

Current Treatment Options

• Glucocorticoid (GC) in high doses is still the first-line treatment of patients with myositis 4.
• There is a general recommendation to combine GCs with another immunosuppressive agent in the early phase of disease to better control disease activity and possibly to reduce the risk for GC-related side effects 4.
• Combining pharmacological treatment with individualized and supervised exercise can be recommended based on evidence 4.
• Immunosuppressive treatment in combination with exercise is recommended for patients with myositis to reduce disease activity and improve muscle performance 4.

Treatment Guidelines and Recommendations

• Most patients with dermatomyositis or polymyositis require treatment with oral high-dose prednisone combined with azathioprine or methotrexate to facilitate early tapering of prednisone 5.
• In case of treatment failure, intravenous immunoglobulin can be tried, followed by rituximab, mycophenolate mofetil, or tacrolimus depending on the specific clinical situation 5.
• A treatment trial with oral prednisone combined with methotrexate is advised in a subgroup of patients with inclusion body myositis 5.
• Glucocorticoids are still considered the mainstay of treatment of myositis but some patients require add-on immunosuppressive therapy because of insufficient response to glucocorticoids, relapses when glucocorticoids are tapered, or because they incur glucocorticoid-related side effects 6.

Future Directions

• There is a need to develop multidisciplinary consensus-driven guidelines which appropriately reflect the diverse and complex nature of the disease 3.
• Subgrouping of patients into clinical and serological subtypes may be a way to identify biomarkers for response to specific immunosuppressive and biological agents and should be considered in future trials 4.
• Novel agents are being tried for refractory manifestations of myositis 6.