From the Guidelines
Myositis and rhabdomyolysis are two distinct conditions, with myositis being inflammation of the muscles and rhabdomyolysis being a severe and potentially life-threatening complication of myositis characterized by the breakdown of muscle tissue.
Key Differences
- Myositis is a rare complication of immune checkpoint inhibitor (ICPi) therapy, characterized by weakness, primarily in the proximal extremities, with difficulties in standing up, lifting arms, and moving around, and can be diagnosed with elevated creatine kinase (CK) levels, electromyography (EMG), and magnetic resonance imaging (MRI) 1.
- Rhabdomyolysis is a severe and potentially life-threatening complication of myositis, characterized by the breakdown of muscle tissue, leading to the release of muscle enzymes, such as CK, into the bloodstream, and can be diagnosed with elevated CK levels, EMG, and MRI 1.
Diagnostic Evaluation
- The diagnostic work-up for myositis and rhabdomyolysis should include a complete rheumatologic and neurologic history, muscle strength examination, and examination of the skin for findings suggestive of dermatomyositis 1.
- Blood testing should include CK, transaminases, lactate dehydrogenase, and aldolase, as well as inflammatory markers, such as erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) 1.
- EMG, imaging (MRI), and/or biopsy may be considered on an individual basis when diagnosis is uncertain and overlap with neurologic syndromes, such as myasthenia gravis, is suspected 1.
Treatment
- The treatment of myositis and rhabdomyolysis typically involves the use of high-dose corticosteroids, such as prednisone, and may require hospitalization for patients with severe weakness, respiratory compromise, or myocardial involvement 1.
- Plasmapheresis, intravenous immunoglobulin (IVIG) therapy, and other immunosuppressant therapy, such as rituximab, may be considered in patients with severe or refractory disease 1.
From the Research
Definition and Characteristics
- Myositis refers to inflammation of the muscles, which can be caused by various factors such as infection, injury, or autoimmune disorders.
- Rhabdomyolysis, on the other hand, is a clinical condition characterized by destruction of skeletal muscle with release of intracellular contents into the bloodstream 2, 3, 4, 5, 6.
Key Differences
- The primary difference between myositis and rhabdomyolysis is the extent of muscle damage. Myositis involves inflammation of the muscles, whereas rhabdomyolysis involves the breakdown of skeletal muscle cells, leading to the release of toxic intracellular material into the systemic circulation 4, 5, 6.
- Rhabdomyolysis can lead to more severe complications, such as acute renal failure, electrolyte disorders, and cardiac arrhythmias, due to the release of myoglobin and other intracellular contents into the bloodstream 2, 3, 4, 5.
Clinical Features and Complications
- Rhabdomyolysis can present with a range of symptoms, from asymptomatic elevations in bloodstream muscle enzymes to life-threatening acute kidney injury and electrolyte abnormalities 2, 3, 4, 5, 6.
- The management of rhabdomyolysis typically involves aggressive fluid administration, urine alkalization, and treatment of electrolyte and metabolic disorders 4, 5.