Polymyalgia rheumatica (PMR) is a rheumatic inflammatory disease that is clinically characterized by pain and morning stiffness in the shoulders, waist, hip and neck. It may be associated with another disease, giant cell arteritis (GCA), and the two disorders may represent different manifestations of a common disease process.
PMR is two to three times more common than GCA. PMR occurs in approximately 50% of patients with GCA, whereas approximately 15% to 30% of patients with PMR over time have GCA. Some patients have manifestations of both disorders at different times.
This disease is almost exclusively a disease of adults over 50 years of age, with a prevalence that progressively increases with age, affecting about 700 per 100,000 people in this age group, although the average age at diagnosis is over 70 years old. In addition, women are affected two or three times more often than men.
Causes of polymyalgia rheumatica
The cause of PMR is unknown, but environmental and genetic factors seem to play a role. In addition to the frequent clinical association between PMR and GCA, there is also evidence of pathogenic similarity between the two disorders. In some cases a cyclic pattern in the incidence is shown, suggesting an infectious trigger of the environment, such as Parvovirus B19, Mycoplasma pneumoniae and Chlamydia pneumoniae .
Symptoms of polymyalgia rheumatica
The most characteristic feature of the presentation of polymyalgia rheumatica is bilateral shoulder pain and stiffness of acute or subacute onset. Patients often also have concomitant pain and stiffness in the waist, hip, neck musculature. Muscle weakness is not a characteristic of the disease, although this may be difficult to assess in the presence of muscle pain; when symptoms are prolonged, muscular atrophy may occur due to disuse.
Also typical is stiffness after periods of rest and morning stiffness of more than one hour. The stiffness can be so deep that patients have great difficulty in turning in the bed, getting out of bed or a chair, or lifting their arms above shoulder height (for example, to comb their hair). They may have mild synovitis (inflammation of the tissue lining the inside of the joint capsule) in the wrists and knees, and rarely in the feet and ankles. Especially at the onset of the disease, most patients have systemic symptoms such as fatigue, loss of appetite, weight loss, low grade fever, and sometimes depression.
Diagnosis of polymyalgia rheumatica
The diagnosis is based mainly on the clinical characteristics described, in people older than 50 years, who present a duration of symptoms more than two weeks. The rheumatology physician should perform basic laboratory tests such as inflammatory markers (erythrocyte sedimentation rate and C-reactive protein), biochemical tests, blood count (number of different cell types in a given amount of blood), or urinalysis .
It is also important to perform imaging tests, including x-rays of inflamed joints, magnetic resonance imaging, ultrasound, scintigraphy, or positron emission tomography (PET-CT). The latter is the best method to thoroughly evaluate the inflammation of PMR and to rule it out from other diseases, such as rheumatoid arthritis, or occult neoplasms.
Treatment of polymyalgia rheumatica
Glucocorticoids are the only known effective treatment. The initial goal of treatment is to rapidly achieve symptomatic control with a relatively low dose of glucocorticoids. After a period of inactivity of the disease, the glucocorticoid dose will slowly begin to decrease. Treatment with glucocorticosteroids can often last for two to three years, although 10% of patients will relapse within 10 years of evolution and require longer treatments. The recommended dose of glucocorticoids is as low as possible to keep the symptoms relieved.
It is also important to prevent and monitor the side effects of glucocorticoids, such as osteoporosis, glucose intolerance and hypertension. If the required maintenance dose of glucocorticoids is high, a glucocorticoid sparing agent should be added to decrease the chance of side effects of glucocorticoids.
In most patients, the PMR has a self-limited course for months or years. However, some patients require long-term treatment and about 10% of patients relapse 10 years after the end of their initial treatment cycle. On the other hand, there is no evidence of increased mortality associated with PMR itself. Thus, all efforts must be made to control the symptoms with a minimum of glucocorticoid side effects.