Causes
The cause of PMR is not well understood. The pain and stiffness result from the activity of inflammatory cells and proteins that are normally a part of the body's disease-fighting immune system, and the inflammatory activity seems to be concentrated in tissues surrounding the affected joints. During this disorder, the white blood cells in the body attack the lining of the joints, causing inflammation. Recent studies have found that inherited factors also play a role in the probability that an individual will develop polymyalgia rheumatica. Several theories have included viral stimulation of the immune system in genetically susceptible individuals.
Infectious disease may be a contributing factor. This would be expected with sudden onset of symptoms for example. In addition, appearance of new cases often appear in cycles in the general population, implying a viral connection. Studies are inconclusive, however several somewhat common viruses were identified as possible triggers for PMR. The viruses thought to be involved include the adenovirus, which causes respiratory infections; the human parvovirus B19, an infection that affects children; and the human parainfluenza virus.
People who have the HLA-DR4 type of human leucocyte antigen appear to have a higher risk of polymyalgia rheumatica.
One reported cause is food sensitivities. Sufferers often do not know they are affected by them, but medical tests exist to verify.
Read more about this topic: Polymyalgia Rheumatica