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.
About Alan Matsumoto, M.D.
Part-time Faculty, Division of Rheumatology
Johns Hopkins University