PMR is a diagnosis of exclusion. As many diseases associated with a systemic inflammatory response can produce muscle and joint pains, careful clinical assessment of a patient presenting with such symptoms is required.
Typically however a patient with PMR presents with either the acute or subacute onset of upper and lower limb girdle pain and stiffness. The pain and stiffness may start asymmetrically or just involve the upper or lower limb girdle.
The patient is generally over the age of 50 and symptoms are usually associated with an elevation in either ESR or CRP. CRP is arguably more sensitive and certainly more specific than the ESR in demonstrating serological evidence of inflammation.
Generally PMR responds to low dose prednisone 15-20 mg per day and this response is seen by many as supporting the diagnosis. In contrast response to high dose prednisone 40-60 mg per day or greater has no clinically discriminatory value. Typically a steroid dose that results in symptom resolution is maintained for 2-4 weeks before gradual reduction. There is no agreed steroid reduction regimen but if a patient starts on 20 mg per day it would be continued for 2 weeks, reduced to 15 mg per day for a further 2-4 weeks, 12.5 mg for 2-4 weeks, then to 10 mg per day with subsequent reduction by approximately 1 mg per month.
It is often necessary to maintain a patient on low dose prednisone, 5-7.5 mg daily, for a period of 6 months or more before complete steroid withdrawal at 1 mg per month. A Synacthen test may be considered at 5 mg daily, to guide further withdrawal.
In those patients suffering relapse the steroid dose should be increased to that required to control symptoms and further attempts made at steroid reduction and withdrawal.
If there are continued relapses and the steroid dose cannot be reduced to below 10 mg per day consideration should be given to the introduction of methotrexate. Referral to a Rheumatologist is recommended in this circumstance.
On average, steroid therapy is maintained for 2-2½ years and therefore there is a risk of steroid induced side effects, in particular osteoporosis. Care should be given to ensuring the patient receives an adequate calcium and vitamin D intake and serum vitamin D levels may need to be measured to ensure no deficiency exists. Patients requiring higher or prolonged doses of prednisone should be referred for a baseline bone density study and consideration of bisphosphonates (see Osteoporosis).