Polymyalgia rheumatica (PMR) is an inflammatory rheumatic condition characterized clinically by aching and morning stiffness in the shoulders, hip girdle, and neck. It can be associated with giant cell (temporal) arteritis (GCA), and the two disorders may represent different manifestations of a shared disease process.
PMR is two to three times more common than GCA. PMR occurs in about 70 percent of patients with GCA, while approximately 15 percent of patients with PMR eventually develop GCA. Some patients have manifestations of both disorders occurring at different times.
Polymyalgia rheumatica (PMR) is almost exclusively a disease of adults over the age of 50, with prevalence that increases progressively with advancing age. The average age at diagnosis is over 70 years. PMR is relatively common, with a prevalence of about 700 per 100,000 persons over 50 years of age. Women are affected two to three times more often than are men.
The cause of PMR is unknown; both environmental and genetic factors appear to play a role. In addition to the frequent clinical association between PMR and GCA, there is also evidence of a pathogenetic similarity between the two disorders. Although pathological findings in PMR are less prominent than in GCA, a mild synovitis characterized by macrophages and CD4+ T lymphocytes has been described in synovial membranes from involved joints. Evidence of subclinical arterial inflammation can be detected in some patients, including the presence of activated dendritic cells, interleukin-1, and interleukin-6. However, unlike GCA, interferon gamma producing T cells are not prominent.
PMR is typically characterized by the subacute or chronic onset of aching and morning stiffness in the shoulders, hip girdles, neck, and torso in patients over the age of 50. The symptoms are usually symmetric. The following features can be seen:
- Stiffness — Morning stiffness typically lasts at least 30 minutes. Difficulty with activities related to the shoulder and hip stiffness may be described by the patient as trouble dressing (eg, fastening a bra normally, donning a shirt or jacket, or pulling on stockings). In some patients, stiffness may be so severe that rising from or turning over in bed represent major obstacles.
- Pain — Shoulder pain is more common at presentation (70 to 95 percent of patients) than is hip and neck involvement (50 to 70 percent). Pain is worse with movement and may interfere with sleep.
- Synovitis and bursitis — About half of patients exhibit distal musculoskeletal manifestations. Palpable synovitis appears to occur in more peripheral joints, such as the knees, wrists, and metacarpophalangeal joints. Synovitis is usually mild and nonerosive, and may be asymmetric.
- Swelling and tenosynovitis — Some patients develop swelling and pitting edema of the hands, wrists, ankles, and top of the feet. The edema usually occurs with other signs of PMR, but can be the presenting symptom. It appears to represent tenosynovitis and synovitis in regional structures.
- Decreased range of motion — There may be decreased active, and sometimes passive, range of motion of the shoulders, neck, and hips.
- Muscle tenderness — Despite the implications of the name "polymyalgia," muscle tenderness is not a prominent feature, and what tenderness there may be about the shoulders is more likely due to synovial or bursal inflammation than muscle involvement.
- Laboratory findings — The characteristic laboratory finding in PMR (and in GCA) is an erythrocyte sedimentation rate (ESR) that is above 40 mm/h (78 to 93 percent in some series), with some patients having values that can exceed 100 mm/H. Some evidence suggests that an elevated serum C-reactive protein (CRP) level is more common than a high ESR.
A normocytic anemia may be present, and the white blood cell and platelet counts are usually normal. In some patients, however, the platelet count is increased as part of a general inflammatory response. Serologic tests, such as antinuclear antibodies, rheumatoid factor, and cyclic citrullinated peptide antibodies are typically negative. Some patients experience an increase in liver enzymes, especially alkaline phosphatase, although this is more common in patients with GCA than PMR alone.
In the absence of any pathognomonic test, we use the presence of each of the following three criteria for the clinical diagnosis of PMR:
- Age 50 years or older at disease onset;
- Bilateral aching and morning stiffness (lasting 30 minutes or more) persisting for at least one month. The stiffness should involve at least two of the following three areas: neck or torso, shoulders or proximal regions of the arms, and hips or proximal aspects of the thighs;
- Erythrocyte sedimentation rate (Westergren) ≥40 mm/h
Symptoms are generally 50 to 70 percent better within three days in patients with PMR started on.
In younger patients, inflammatory rheumatic diseases that may mimic PMR are more prevalent than PMR itself; the diagnosis in these patients thus necessitates careful consideration of alternative diagnoses.
Asymmetric symptoms may be present especially early in disease, beginning in one shoulder or hip, but soon become bilateral in most patients.
Evaluation for GCA
There is considerable overlap in the diagnoses of PMR and GCA. Patients with "pure" PMR lack the classic findings of GCA such as temporal artery tenderness, headache, jaw pain, visual loss, and evidence of noncranial ischemia (such as arm claudication or cerebral ischemia). In the absence of such signs or symptoms, we do NOT routinely perform a temporal artery biopsy, since a positive result is rare in this setting.
Patients with a marked inflammatory response, such as a high fever (at least 39ºC) or a lack of response to 20 mg/day of prednisone may have an abnormal temporal artery biopsy if performed. However, we do not routinely biopsy such patients since they seldom develop ischemic complications.