If your doctor strongly suspects PMR, you will receive a trial of low-dose corticosteroids. Often, the dose is 10–15 milligrams per day of prednisone (Deltasone, Orasone, etc.). If PMR is present, the medicine quickly relieves stiffness. The response to corticosteroids can be dramatic. Sometimes patients are better after only one dose. Improvement can be slower, though. But, if symptoms do not go away after two or three weeks of treatment, the diagnosis of PMR is not likely, and your doctor will consider other causes of your illness.
Infectious disease may be a contributing factor. This would be expected with sudden onset of symptoms, for example. In addition, new cases often appear in cycles in the general population, implying a viral connection. Studies are inconclusive, but 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 .  Some sufferers attribute the onset of PMR to stress.