Definition and Epidemiology

Polymyalgia rheumatica (PMR) is a treatable, chronic systemic inflammatory condition of unknown cause seen in the elderly. Most patients are Caucasian, and, in general, PMR does not occur in patients younger than age 50. It is characterized by diffuse aching and stiffness of the shoulder girdle, neck, and pelvic girdle and is associated with elevated erythrocyte sedimentation rate (ESR) and/or C-reactive protein (CRP). There are no specific laboratory tests for PMR, and the diagnosis is made on clinical grounds and after exclusion of other inflammatory conditions.¹

The incidence of PMR increases progressively with age, peaking 70 to 80 years. Women are affected two to three times more often than men. A population-based study in the United States found prevalence as high as 1 per 133 persons older than age 50 years.²

Pathophysiology

The cause of PMR is not known; however, genetic, immune, and environmental influences are believed to be important factors. Human leukocyte antigen HLA-DRB1 genotypes and polymorphisms in genes involved in immunity, including those involved with tumor necrosis factor-α (TNF-α) and interleukin-1 (IL-1), are associated with increased susceptibility and/or severity of PMR. The higher incidence of PMR during winter months and the known variation in geographic distribution of the disease in the same country, including a higher prevalence in rural areas than in urban communities, implies a role for environmental factors.³ The possible role of infectious agent(s) as a trigger of the disease has been suspected; however, no definite proof has been found.

Clinical Presentation

The most remarkable features are the stiffness and aching of the shoulder girdle, pelvic girdle, and neck. Inflammatory in origin, the pain tends to be worse at night and may radiate distally to the elbows and the knees. Morning stiffness lasting longer than 1 hour and often all morning is common. The onset can be acute, such that the patient may remember the day and the hour of the onset. In most patients the onset is subacute and insidious. About half of patients experience systemic symptoms such as low-grade fever, depression, fatigue, malaise, and weight loss. About 25% of patients have inflammatory arthritis involving primarily the knees and wrists and less frequently the metacarpal joints. It can be mistaken for rheumatoid arthritis; however, in PMR the inflammatory arthritis is non-erosive, asymmetric, self-limiting, and highly responsive to systemic corticosteroids.^1,4 Tenosynovitis of the extensor tendons of the hands and feet can be seen in association with peripheral arthritis. Remitting seronegative symmetric synovitis with pitting edema syndrome (RS3PE) seen in 12% of PMR patients is characterized by pitting edema of the dorsum of the hands and wrists and sometimes on the dorsum of the feet.¹

Physical examination reveals painful active motion of the shoulders and hips with limited range of motion. No signs of synovitis are present except in those with peripheral arthritis. True muscle weakness is absent; however, muscle strength is often difficult to assess because of the pain.

Diagnostics

When PMR is suspected on clinical grounds, the following initial laboratory tests are recommended:

Differential Diagnosis

Nonrheumatic medical conditions that may mimic PMR in a patient aged 50 years or older include active malignancy such as lymphoma and multiple myeloma, active bacterial or viral infections, hypothyroidism, and drug-induced syndromes such as statin myopathy.⁶

Rheumatic diseases that should be in the differential diagnosis include elderly onset RA, late-onset seronegative spondyloarthropathies, late-onset systemic lupus erythematosus (SLE), inflammatory myopathies, calcium pyrophosphate arthritis, and chronic pain syndromes such as osteoarthritis of the neck and shoulders. Giant cell arteritis (GCA) may occur concomitantly with PMR (see later). Elderly onset RA differs from PMR with the presence of subcutaneous nodules, anti-CCP antibodies, and rheumatoid factor in the latter. Moreover, the clinical response to steroid therapy is more dramatic in PMR.

Management

Systemic corticosteroids remain the standard drug therapy, although there have been no placebo-controlled trials. Low-dose prednisone typically induces a rapid response within a few days of initiation of therapy. The usual starting dose is 15 mg to 20 mg of prednisone (or equivalent) daily. A higher dose of prednisone (60 mg daily) is used when there is evidence of concomitant GCA (see later).

The 2015 EULAR recommendations include an initial dose of 12.5 to 25 mgs of prednisone daily with strong recommendations against using doses higher than 30 mg/day. Begin tapering doses by 5 mgs a week after 4-8 weeks of therapy and continue using the lowest effective dose.⁷ Nonsteroidal anti-inflammatory agents are not recommended.

There is no optimal corticosteroid regimen for every patient; thus the regimen should be flexible and individualized. There is variation not only in severity, but also in the presentation and course of the illness.

A marked overall clinical improvement within a week of corticosteroid therapy is expected, and laboratory abnormalities should improve within 4 to 8 weeks. The patient should be monitored for pain, morning stiffness, functional disability, osteoporosis risk, adverse drug reaction, and an alternative diagnosis. The majority of PMR patients are continued on low-dose corticosteroids for 1 to 2 years. PMR patients with concomitant GCA appear to require a longer duration of corticosteroid therapy.

Complications

Despite good clinical response to drug therapy, disease relapses are common and are seen in 50% of cases. Factors associated with high relapse rate include persistently elevated inflammatory markers, female sex, and rapid taper of corticosteroid dose.⁸

Adverse drug side effects including osteoporosis, fragility fractures, diabetes, hypertension, and cardiovascular events are not uncommon. Sixty-five percent of PMR patients treated with corticosteroid alone and 80% of those who receive corticosteroids and NSAIDS experience at least one adverse event.⁹ Patients with long-standing PMR, especially those with high risk for corticosteroid side effects, should be maintained at the lowest dose possible. In addition, the use of a steroid-staring agent such as methotrexate, leflunomide, or azathioprine may be considered.

Bone protective measures (calcium, vitamin D, and bisphosphonates) are recommended for patients on chronic corticosteroid therapy.

The overall life survival of PMR patients appears to be better than that of the general population, and this may be in part a result of improved surveillance and medical follow-up.¹⁰

Indications for Referral

Patients with PMR should be referred to a rheumatologist for definitive diagnosis and a prescription regimen. Follow-up can be managed by primary care providers with access to rheumatologists for questions or for patients not responding to usual regimens. Any patients with symptoms suggestive of temporal arteritis (see later) should also be referred to an ophthalmologist.