From the Guidelines
The diagnosis and treatment of myositis should prioritize the use of high-dose corticosteroids, such as prednisone, starting at 1 mg/kg/day, and may include the addition of immunosuppressants like methotrexate, azathioprine, or mycophenolate mofetil for patients who do not respond adequately or to reduce steroid dependency, as recommended by the most recent guidelines 1.
Diagnosis of Myositis
Myositis is an inflammatory condition affecting the muscles, characterized by muscle weakness, pain, and fatigue. It includes several subtypes such as dermatomyositis, polymyositis, and inclusion body myositis. The diagnosis of myositis involves a combination of clinical evaluation, laboratory tests, and imaging studies. Key diagnostic features include:
- Muscle weakness, particularly in the proximal muscles
- Elevated muscle enzymes, such as creatine kinase (CK)
- Abnormal electromyography (EMG) findings
- Characteristic findings on muscle biopsy
Treatment of Myositis
The treatment of myositis typically involves the use of corticosteroids, such as prednisone, to reduce inflammation and suppress the immune system. The initial dose of prednisone is usually 0.5-1 mg/kg/day, with a gradual taper over several weeks or months. For patients who do not respond adequately to corticosteroids or who experience significant side effects, immunosuppressants such as methotrexate, azathioprine, or mycophenolate mofetil may be added to the treatment regimen.
Management of Severe Myositis
In cases of severe myositis, particularly those with life-threatening manifestations such as myocarditis or respiratory failure, more aggressive treatment may be necessary. This may include:
- High-dose corticosteroids, such as methylprednisolone
- Intravenous immunoglobulin (IVIG)
- Plasmapheresis
- Other immunosuppressant therapies, such as rituximab or cyclophosphamide
Monitoring and Follow-up
Regular monitoring of patients with myositis is essential to assess treatment response, adjust the treatment regimen as needed, and prevent complications. This includes:
- Regular blood tests to check muscle enzymes and medication effects
- Periodic assessment of muscle strength and function
- Monitoring for side effects of medications, including increased infection risk
Recent Guidelines and Recommendations
Recent guidelines and recommendations for the diagnosis and treatment of myositis emphasize the importance of early diagnosis and treatment to prevent irreversible muscle damage and improve long-term outcomes 1. These guidelines also highlight the need for a multidisciplinary approach to care, involving rheumatologists, neurologists, and other specialists as needed.
From the Research
Diagnosis of Myositis
- The diagnosis of myositis involves a combination of clinical assessment, laboratory investigations, and muscle biopsy 2, 3, 4.
- Symptoms such as symmetrical proximal muscle weakness, elevated creatine kinase, CRP or ESR, and electromyography and muscle biopsy provide important diagnostic clues 2.
- Pharyngeal, respiratory, cardiac, and neck muscles may also be affected, and pulmonary function tests should be part of the diagnostic workup 2.
- Cutaneous manifestations, such as skin lesions, can be a characteristic and crucial diagnostic criterion for dermatomyositis 2.
Treatment of Myositis
- Corticosteroids are the therapy of choice in myositis, with a dosage of 1-2 mg/kg 2.
- Additional immunosuppressive therapy, such as azathioprine or methotrexate, is frequently required 2, 3, 5.
- In case of insufficient therapeutic response, the use of intravenous immunoglobulins or rituximab may be justified 2, 3, 5.
- Acute therapeutic management is usually followed by low-dose maintenance therapy for one to three years 2.
- Topical corticosteroids and calcineurin inhibitors may be effective in treating skin lesions, while systemic therapies such as antimalarial agents, methotrexate, and corticosteroids may also be helpful 2.
Special Considerations
- Approximately 30% of patients with dermatomyositis may develop interstitial lung disease, and pulmonary function tests should be part of the diagnostic workup 2.
- About 30% of adult dermatomyositis cases are associated with a malignancy, but this should not delay the treatment of severe myositis 2.
- HIV-associated myositis occurs at any stage of HIV infection and has a relatively good prognosis, responding well to immunosuppressive therapy 6.
- A thorough clinical assessment, including a detailed family history, complemented by electromyography and creatine kinase measurements, should be undertaken in any patient with presumed idiopathic inflammatory myopathy 4.