What is Polymyalgia Rheumatica?
Polymyalgia rheumatica (PMR) is an autoimmune disease that causes an inflammatory reaction affecting the lining of joints, especially the shoulders and hips, and sometimes the arteries and some major branches of the aorta. It’s the second-most common rheumatic disease after rheumatoid arthritis, and is the most common inflammatory disease in the elderly.
What causes Polymyalgia Rheumatica?
Currently, the exact cause of PMR is unknown, but environmental and genetic factors are thought to be important.
How common is Polymyalgia Rheumatica?
Data from population-based studies estimate that about 59 out of 100,000 people over the age of 50 will develop PMR in a one-year period. The lifetime risk for developing PMR is about 2.4% in women and 1.7% in men.
Who gets Polymyalgia Rheumatica?
PMR is the most common form of new-onset inflammatory arthritis in the elderly. It occurs in people over age 50, and most commonly first shows up in people over the age of 70. PMR seems to be more common in rural than in urban regions, and more frequently occurs in people of Northern European ancestry. It’s rare in other ethnic groups like Asians and persons of African descent.
There is a close association between giant cell arteritis (GCA) and PMR. Although estimates vary somewhat, approximately 20% of patients with PMR will develop GCA, while about half of patients with GCA also have symptoms of PMR.
PMR primarily affects large joints and their surrounding structures such as the bursa, the small fluid-filled sacs that cushion joints. It causes severe stiffness and pain in the shoulders, hips and neck that’s worse in the morning and improves as the day goes on. Rarely, some patients may even have diffuse swelling of the hands, forearms and feet, and symptoms of carpal tunnel syndrome. Almost all patients with PMR have these symptoms of pain and stiffness in both shoulders. Not all of the other symptoms are present in every patient. The symptoms usually start suddenly, often from one day to the next. Common symptoms include:
• New pain and stiffness in both shoulders, hips, and neck
• New difficulty in raising the arms above the head, or even combing one’s hair
• Low-grade temperatures
• Mild weight loss and poor appetite
• New onset of depression
Diagnosis is based on one or more of the symptoms and physical findings listed above, as well as blood studies showing inflammation. Physical examination often reveals that patients are unable to raise their arms above their heads at the start of the disease. Blood tests can identify erythrocyte sedimentation rate and/or C-reactive proteins that abnormally high in most patients with PMR. In some cases, imaging of the shoulders and/or hips with ultrasound or magnetic resonance imaging may also help make a diagnosis.
PMR is very treatable. The only drug which is known to be a consistently effective therapy is prednisone (or another corticosteroid of the same family), which works by decreasing inflammation. Methotrexate, a medication commonly used to treat rheumatoid arthritis and some other rheumatic diseases, has been used to reduce disease flares, but is not of certain benefit. Blood tests — including the erythrocyte sedimentation rate or C-reactive protein — will be done every few weeks to months to determine if the inflammation is still active. Most people require about 3 years of treatment, but duration varies widely.
What are the complications?
The most common complications of PMR occur when patients develop GCA, which usually happens at the start of PMR. GCA symptoms include new onset headache, sometimes tenderness of the scalp, and vision changes that can progress to blindness. Rarely, patients can develop inflammation of vessels of the arms, legs, and aorta leading to narrowing of the blood vessel or to formation of aneurysms (widening or ballooning of the blood vessel). Some side-effects of prednisone use include osteoporosis, diabetes and cataracts.
The prognosis is generally good. Most patients have rather dramatic improvement of their pain and stiffness within 24 to 72 hours of starting prednisone treatment. The disease usually resolves by itself within 3 years, but it’s highly variable. Patients with PMR have a normal life expectancy. It’s important to be attentive to minimizing and managing the possible side-effects of prednisone therapy.
What’s new in Polymyalgia Rheumatica?
Other treatments are currently the subject of investigation. Recently, it has been recognized that patients with PMR are at higher risk for atherosclerosis, or hardening of the arteries, although life expectancy overall is not affected. Other investigations are being undertaken to identify the causes and the biology of PMR, which will improve treatment of this disease.
Revision: September 2012