Myalgia

Overview
Myalgia means "muscle pain" and is a symptom of many diseases and disorders. The most common cause for myalgia is either overuse or over-stretching of a muscle or group of muscles. Myalgia without a traumatic history is often due to viral infections. Longer-term myalgias may be indicative of a metabolic myopathy, some nutritional deficiencies or chronic fatigue syndrome.

Differential diagnosis of causes of myalgia
The most common causes of myalgia are overuse, injury or stress. However, myalgia can also be caused by diseases, disorders, medications, as a response to vaccination and withdrawal syndromes.

Overuse
Overuse of a muscle is using it too much, too soon and/or too often. Examples are:
 * Repetitive strain injury.

Injury
The most common causes of myalgia by injury are: sprains and strain (injury).

Infectious
Trichinosis, Typhoid fever, Upper respiratory tract infection, Viral pneumonia, Influenza, Common cold, Community-acquired pneumonia, Coccidioidomycosis, Dengue, Endemic typhus, HIV, Infectious mononucleosis, Legionellosis, Leptospirosis, Lyme disease, Malaria, Marburg virus, Meningitis, Monkeypox, Pharyngitis, Pneumonia, Prostatitis, Psittacosis, Q fever, Rabies, Rift Valley fever, Severe acute respiratory syndrome (SARS), Toxic shock syndrome, West Nile, Chikungunya

Autoimmune
Multiple sclerosis, Myositis, Lupus erythematosus, Familial Mediterranean fever, Polyarteritis nodosa, Devic's disease, Morphea

Metabolic defect
Carnitine palmitoyltransferase II deficiency, Conn's syndrome, Adrenal insufficiency

Other
Chronic fatigue syndrome, Hypokalemia, Exercise intolerance, Mastocytosis, Peripheral neuropathy, Eosinophilia myalgia syndrome, Fibromyalgia, Barcoo Fever, Delayed onset muscle soreness

Medications
Aldara, Acrylamide, Darbepoetin, Isotretinoin, Procainamide, Quinupristin/dalfopristin, Spiriva, Sumatriptan, Vardenafil, Statins, Zetia, Zomig, Boniva

As a Response to Vaccination
A moderate occurrence (25-35%) of myalgia in recipients of tetanus vaccination is identified in the US; it presents in the large muscle groups and at the subcutaneous injection site. When a patient returns with these symptoms (which include fever, poor appetite and lethargy), a clinician who fails to notice the recent tetanus vaccination on the patient's chart is in danger of making a life-threatening misdiagnosis.
 * An item of note is that in heart patients using selective β1-blockers such as metoprolol, incidence of myalgia after tetanus vaccination is significantly higher.

Withdrawal Syndromes
Sudden cessation of opioids, barbiturates, benzodiazepines, or alcohol can induce myalgia.

Myalgia Video

 * Video on Myalgia

Related chapters

 * Delayed onset muscle soreness
 * Myopathy
 * Myelitis

Resources

 * NEUROMUSCULAR DISEASE CENTER Washington University

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