Several risk factors are associated with polymyalgia rheumatica (PMR). These risk factors, as well the possible causes of PMR are described below.
- Advanced age. The risk of PMR is known to increase with age. The condition is rarely seen in people under 50 years of age. Most cases involve people 75 years and older.1
- Female sex. Women are approximately 2 to 3 times more likely to be affected by PMR than men.2
- Northern European descent. People of any ethnicity can develop PMR. However, Caucasian people of northern European descent appear to be at a significantly higher risk.3
Not everyone with these risk factors will develop PMR. The presence of these risk factors only increases the likelihood of developing PMR.
Possible Causes of Polymyalgia Rheumatica
Several potential causes for PMR are being investigated. Some of the theories put forward by researchers include:
- Genetic predisposition. A specific gene called HLA-DR4 that is associated with rheumatoid arthritis is also present in many cases where PMR and giant cell arteritis occur together. Experts speculate this gene triggers the condition, although this is not a conclusive cause in PMR.4-5
- Immunology. Blood tests indicate immune system cells penetrating the synovial membrane of joints and tendons, resulting in inflammation. This is similar to the autoimmune process in which the body tissues are attacked by its own immune system.4
- Infection. The sudden start of PMR and the nature of the symptoms like joint pain, fever, and malaise, are suspected to be a result of infections caused by viruses.4
- Environmental factors/exposure to sunlight. Damage of superficial arteries by over exposure to ultra violet radiation from the sun is another proposed cause for the development of PMR. Some studies suggest the elastic fibers present in the arteries and synovial membranes are damaged by ultra violet rays. These damaged tissues may get infected by viruses that remain dormant for a long time and may get reactivated later, causing PMR.4
These same risk factors and possible causes are also seen in giant cell arteritis. Expert analysis indicates 40% to 60% of giant cell arteritis cases eventually develop PMR. There is also a 9% to 20% risk of PMR cases developing giant cell arteritis.6 Diagnostic tests of blood samples and genetic components reveal similar findings for PMR and giant cell arteritis, leading experts to see these conditions as two ends of the same disease spectrum.