Inflammation's Impact on Muscle

Harmful Effects of Inflammation on Muscle

Muscle inflammation can lead to muscle weakness and elevated muscle enzymes, potentially endangering life, especially when respiratory or cardiac muscles are affected, according to the American College of Oncology 1
Inflammatory myopathies, such as polymyositis and dermatomyositis, are characterized by symmetric proximal muscle weakness with CD8+ cytotoxic T-cell invasion of non-necrotic muscle fibers, as stated by the Mayo Clinic 2
Muscle weakness is more typical of myositis than pain, which is an important characteristic for clinical diagnosis, as noted by the American College of Oncology 3
Systemic inflammatory response syndrome affects all related metabolic pathways, including changes in protein metabolism, fat and muscle mass loss, and increased acute-phase protein production, according to Clinical Nutrition 4
Severe muscle mass depletion is closely related to mortality, surgical complications, and chemotherapy dose-limiting toxicity in cancer patients, as reported by Clinical Nutrition 5

For moderate to severe myositis, immediate initiation of prednisone 0.5-1 mg/kg or equivalent corticosteroid therapy is recommended, as stated by the American College of Oncology 1
In cases of severe weakness with or without pain, limiting self-care ability, hospitalization and initiation of prednisone 1 mg/kg or equivalent should be considered, according to the American College of Oncology 3
Immune checkpoint inhibitor-induced myositis is rare but potentially fatal, with a mortality rate of up to 20%, primarily due to concomitant myocarditis, and requires immediate discontinuation of immune therapy and initiation of high-dose corticosteroids, IVIG, and/or plasma exchange, as noted by the American College of Oncology and other sources, but the non-Praxis source is 3
For newly diagnosed uncomplicated inflammatory myopathies, immediate initiation of high-dose corticosteroids, usually prednisone 1 mg/kg/day, along with steroid-sparing agents such as methotrexate, azathioprine, or mycophenolate, is suggested, as recommended by the Mayo Clinic 7
Due to the potential need for long-term treatment, physicians should consider initiating steroid-sparing agents earlier than for other immune-related adverse events, according to the American College of Oncology 1