Polymyalgia rheumatica (PMR) is an inflammatory disorder. It results in muscle pain and stiffness in the body. The effects are most common in the shoulders, arms, hips, and thighs. About 15% of people with PMR will also develop giant cell arteritis (GCA). GCA is an inflammation of the lining of the arteries, the blood vessels that carry blood away from the heart.

Giant Cell Arteritis
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The exact cause is not known. Inflammatory conditions may be due to some problem with the immune system. Some evidence suggests that certain viruses could be responsible for PMR. Genetic factors may also play a role.