From the Guidelines
Myalgia is most commonly caused by overexertion, injury, tension, or stress on muscles, but can also be triggered by viral infections, bacterial infections, autoimmune disorders, fibromyalgia, certain medications such as statins, electrolyte imbalances, dehydration, and poor circulation. The causes of myalgia can be diverse, ranging from physical factors like overexertion and injury, to infections such as influenza and COVID-19, which can trigger widespread muscle pain as the immune system responds to the infection 1. Autoimmune disorders, including lupus, rheumatoid arthritis, and polymyalgia rheumatica, involve the immune system attacking healthy tissues, resulting in muscle pain. Fibromyalgia is another significant cause, characterized by widespread pain and tenderness, affecting approximately 2% of the general population 1. Certain medications, particularly statins used to lower cholesterol, can cause muscle pain as a side effect, with myalgias occurring in 1% to 5% of patients in randomized controlled trials (RCTs) and up to 10% in observational studies and clinical settings 1. Electrolyte imbalances, especially low levels of potassium, calcium, or magnesium, may lead to muscle cramping and pain, while dehydration and poor circulation can also contribute to muscle pain. Chronic conditions like hypothyroidism can manifest with muscle pain as a symptom. Treatment depends on identifying and addressing the underlying cause, which may involve rest, hydration, anti-inflammatory medications, or specific treatments for the primary condition. In cases of immune-related adverse events, such as those associated with immune checkpoint inhibitor therapy, management of myositis and other musculoskeletal symptoms may require temporary or permanent discontinuation of the therapy, along with the use of corticosteroids, synthetic or biologic disease-modifying antirheumatic drugs, and other supportive measures 1. It is essential to conduct a thorough assessment of symptoms, evaluate for non-statin etiologies, assess predisposing factors, and perform a physical exam to determine the cause of myalgia and guide appropriate treatment.
From the Research
Myalgia Causes
- Myalgia is a common symptom of various neuromuscular disorders, including metabolic muscle diseases, inflammatory muscle diseases, dystrophic myopathies, and myotonic muscle disorders 2
- Drugs can also cause myalgias and myopathies through various mechanisms, with statin-induced myopathy being one of the most commonly recognized and studied myopathies 3
- Myalgia can be associated with many diseases, including fibromyalgia, neurodegenerative diseases, and degenerative spine diseases, with a lifetime prevalence of 60-85% 4
- Tissue acidosis is a known source of muscle pain, with experimental muscle pain induced by intramuscular infusion of a buffered acidic solution in humans 4
- Oxidative stress can also activate proton-sensing ion channels and trigger fibromyalgia-like pain in mice 4
Factors Contributing to Myalgia
- Inflammatory etiologies, such as dermatomyositis, can cause myalgia 2
- Endocrine disorders, such as hypothyroidism, can also contribute to myalgia 2
- Genetic predisposition can increase the risk of statin-induced myopathy 3
- Concomitant use of other drugs metabolized by the cytochrome P450 system can also increase the risk of myopathy 3
Diagnosis and Treatment
- Basic diagnostic workup for myalgia includes a detailed medical history, full neurologic assessment, laboratory tests, EMG, and nerve conduction studies 2
- Muscle imaging, genetic testing, and muscle biopsy may be required to make a diagnosis 2
- Treatment for myalgia should aim to improve or correct the underlying cause, such as inflammation or hypothyroidism 2
- Symptomatic therapy for myalgia can include medications such as mexiletine, carbamazepine, phenytoin, pregabalin, gabapentin, or amitriptyline 2