The pain of FMS and PMR can be similar and difficult to distinguish. Both can have diffuse joint and soft tissue tenderness and stiffness. The joint examination in both generally does not show any swelling or restriction in range of motion. However active PMR is associated with a high sed rate and responds well to prednisone and other anti-inflammatories. FM does not respond to prednisone. Neither FM nor PMR has the rash you describe. In general, PMR should be more responsive to the doses of prednisone and MTX you mention.
Polymyalgia AND Fibromyalgia
My wife has been diagnosed with Polymyalgia and Fibromyalgia (high sed. rate, trigger points, pain in arms, legs, groin & etc.) She has been on prednisone for apprx. 9 mo. and methotrexate for 6 mo, now up to 15 mg. She has never been able to get below 15 mg. prednisone along with MTX without huge pains. Below 12 mg. pred. her sed. rate goes up. Now the bicep area of one of her arms is swollen with red splotches apprx. 5 places that have kinda combined into one red area about the size of a teacup, it looks like it has a deep bleeding in it. She says at times it feels as though the meat is being pulled from the bone. It has a continual dull toothache like ache in it. Is this commom to PMR/FMS? MTX makes her nauseous and weak for about four days, but she continues to take it and hope.