LAS VEGAS – Up to 30% of patients diagnosed with polymyalgia rheumatica actually have a different disease, according to Dr. Eric L. Matteson.
The proximal pain and stiffness syndrome, which is a commonly accepted phenotype of polymyalgia rheumatica (PMR), also occurs in many other rheumatologic and inflammatory illnesses, Dr. Matteson said at the annual Perspectives in Rheumatic Diseases. Laboratory tests are nonspecific, and there is significant overlap – in terms of pathobiology – with other forms of inflammatory diseases associated with synovitis and vasculitis. Further, multiple conditions can coexist – including osteoarthritis, rotator cuff lesions, secondary capsulitis, and other periarticular lesions – and several conditions can mimic PMR.
Dr. Matteson of the Mayo Clinic College of Medicine, Rochester, Minn., described one 73-year-old patient with “discitis” who was initially thought to have PMR. She was admitted to the hospital with acute stiffness in the shoulder and acute onset backache. In keeping with a PMR diagnosis, her C-reactive protein (CRP) level was 113 mg/L, and she responded to 20 mg of prednisolone.
Dr. Eric L. Matteson
Another case involved a 63-year-old man with metastatic cancer. He presented with typical symptoms of PMR, a CRP level of 150 mg/L, and an alkaline phosphatase level of 1.5 times the upper limit of normal. He did not respond to 15 mg/day of prednisolone but felt better on 30 mg/day, with alkaline phosphatase rising to three times the upper limit of normal.
A third case involved a patient with antineutrophil cytoplasmic autoantibody vasculitis who was initially thought to have PMR. The patient presented with constitutional symptoms and was started on 15 mg/day of oral prednisone. Hemoptysis occurred 4 weeks later.
In an effort to improve diagnosis, the American College of Rheumatology (ACR) and the European League Against Rheumatism (EULAR) developed consensus candidate classification criteria. An expert panel that included Dr. Matteson had recognized that opinions differ as to the definition of PMR and its treatment, and that classification criteria are needed. In pursuit of this goal, the panel identified seven core criteria that 70% of survey respondents agreed upon, including age of 50 years or older, duration of at least 2 weeks, bilateral shoulder and/or pelvic girdle aching, morning stiffness duration of more than 45 minutes, elevated erythrocyte sedimentation rate (ESR), elevated CRP level, and rapid corticosteroid response with greater than 75% global response within 1 week to 15-20 mg of prednisolone or prednisone daily.
In addition, more than 70% of survey respondents agreed on the importance of assessing shoulder pain and limitation and/or hip motion. Agreement was low for peripheral signs such as carpal tunnel syndrome, tenosynovitis, and peripheral arthritis (J. Rheumatol. 2008;35:270-7).
Dr. Matteson suggested a stepwise approach to diagnosis, which includes evaluating for inclusion criteria, evaluating for exclusion criteria, prescribing steroids and evaluating patient response, and confirming the diagnosis at follow-up.
Inclusion criteria include age of 50 years or older, bilateral shoulder or pelvic girdle aching, morning stiffness for at least 45 minutes, symptom duration of at least 2 weeks, and acute phase response with an ESR greater than 30 mm/hr or a CRP level greater than 10 mg/L. All of these features must be present, he said at the conference held by Global Academy for Medical Education.
The panel also found that typical findings of synovitis in the shoulder and hip regions can assist in the classification of PMR.
Core exclusion criteria include active infection, neoplasia, and giant cell arteritis. Other criteria that reduce the likelihood that PMR is present include rheumatoid arthritis, ankylosing spondylitis, systemic lupus erythematosus, and inflammatory myopathy.
Drug-induced myalgia, pain syndromes, endocrine disorders, and Parkinson’s disease are mimics of PMR and must be excluded.
Corticosteroid response should be carefully assessed in those thought to have PMR, and the response should be rapid, complete, and sustained. Especially high doses increase the probability of diagnostic error, and nonresponse is an indication for reevaluation of the diagnosis and reassessment of the disease, Dr. Matteson said.
A scoring algorithm that incorporates ultrasound findings is also useful in the evaluation of a patient with suspected PMR. In patients aged 50 years or older with bilateral shoulder aching and abnormal ESR/CRP levels, points are awarded as follows: 2 points for morning stiffness for more than 45 minutes, 1 point for hip pain or limited range of motion, 2 points for normal rheumatoid factor or anticitrullinated peptide antibodies (ACPAs), 1 point for the absence of other joint pain. Further, 1 point is awarded if ultrasound identifies subdeltoid bursitis, biceps tenosynovitis, or glenohumeral synovitis in at least one shoulder. Also, 1 point is awarded if ultrasound shows subdeltoid bursitis, biceps tenosynovitis, or glenohumeral synovitis in both shoulders.