(See also Overview of Vasculitis.)
Polymyalgia rheumatica affects adults > 55; the female:male ratio is 2:1.
Because polymyalgia rheumatica is closely associated with giant cell arteritis, some authorities consider the two disorders to be different aspects of the same process. Polymyalgia rheumatica appears to be more common. A few patients with polymyalgia rheumatica develop giant cell arteritis, but 40 to 60% of patients with giant cell arteritis have polymyalgia rheumatica. Polymyalgia rheumatica may precede, follow, or occur simultaneously with giant cell arteritis.
Etiology and pathogenesis of polymyalgia rheumatica are unknown. Ultrasound and MRI findings suggest that they probably result from low-grade axial synovitis and bursitis.
Polymyalgia rheumatica is characterized by bilateral proximal aching of the shoulder and hip girdle muscles and the back (upper and lower) and neck muscles. Stiffness in the morning is typical and lasts > 60 minutes. Shoulder symptoms reflect proximal bursitis (eg, subdeltoid, subacromial) and less often bicipital tenosynovitis or joint synovitis. Discomfort may awaken patients from sleep and is worse in the morning; occasionally it is severe enough to prevent patients from getting out of bed and from doing simple activities. The pain may make patients feel weak, but objective muscle weakness is not a feature of the disorder.
Polymyalgia rheumatica is suspected in older patients with typical symptoms, but other possible causes must be excluded.
Tests include erythrocyte sedimentation rate (ESR), C-reactive protein, complete blood count, thyroid-stimulating hormone levels, and CK. In > 80% of patients, ESR is markedly elevated, often > 100 mm/hour, usually > 50 mm/hour (Westergren method). C-reactive protein is also elevated. Electromyography, biopsy, and other tests (eg, rheumatoid factor), which are normal in polymyalgia rheumatica, are sometimes done to rule out other clinically suspected diagnoses.
The following findings in polymyalgia rheumatica distinguish it from
Rheumatoid arthritis: In polymyalgia rheumatica, chronic small-joint synovitis, erosive or destructive lesions, rheumatoid nodules, and rheumatoid factor are absent in about 80% (although some joint swelling may be present) of patients. Differentiation from rheumatoid arthritis may be difficult in the remaining 20%.
Autoimmune myositis: In polymyalgia rheumatica, pain rather than weakness predominates; muscle enzyme levels and electromyography and muscle biopsy results are normal.
Hypothyroidism: In polymyalgia rheumatica, thyroid function test results and muscle enzyme levels are normal.
Multiple myeloma: In polymyalgia rheumatica, monoclonal gammopathy is absent.
Fibromyalgia: In polymyalgia rheumatica, symptoms are more localized, ESR is typically elevated, and pain is present with palpation and range of motion (active and passive) of the shoulders, even when the patient is distracted.
Prednisone started at 15 to 20 mg orally once a day results in dramatic improvement, often very rapid (in hours or days), and this response can help support the diagnosis. If giant cell arteritis is thought to be present, the dose of corticosteroids should be higher, and temporal artery biopsy should be done.
Treatment effectiveness is monitored by symptoms, ESR, and C-reactive protein. As symptoms subside, corticosteroids are tapered to the lowest clinically effective dose, regardless of ESR. C-reactive protein is more helpful than ESR in guiding response to treatment because ESR may be persistently elevated in older patients because of other reasons. Some patients are able to stop corticosteroids in about 2 years, even sooner without relapse, whereas others require small doses for years. Nonsteroidal anti-inflammatory drugs (NSAIDs) are rarely sufficient.
Some patients who are unable to have their prednisone dose tapered and who have frequent recurrences may benefit from the addition of methotrexate (10 to 15 mg orally once a week), if renal function is normal. Adding a second drug in polymyalgia rheumatica is controversial because controlled randomized trials have shown minimal or no benefit. Trials using anti-tumor necrosis factor (TNF) drugs (infliximab and adalimumab) and rituximab have not shown benefit.
In older patients, physicians should watch for and treat complications of corticosteroid use (eg, diabetes, hypertension). Patients taking prednisone long term should be given a bisphosphonate to prevent osteoporosis.
Giant cell arteritis may develop at the onset of polymyalgia rheumatica or much later, sometimes even after patients appear cured of the disorder. Therefore, all patients should be instructed to immediately report headache, muscle pain during chewing, and, particularly, visual disturbances to their physician.
Polymyalgia rheumatica affects adults > 55, causing proximal myalgias and stiffness.
It is present in 40 to 60% of patients with giant cell arteritis.
Diagnose clinically, sometimes with supportive evidence of an elevated ESR and dramatic response to low to moderate doses of corticosteroids.
Treat with corticosteroids, eventually tapering if possible.
Warn patients about symptoms of giant cell arteritis.