Polymyalgia rheumatica

Practical management of PMR in primary care.

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By  Healthcare Middle East Published  November 6, 2006

Polymyalgia rheumatica (PMR) is an inflammatory condition of unknown cause characterised by aching and morning stiffness in the cervical region and shoulder and pelvic girdles.

First identified by Bruce in 1888, who named it “senile rheumatoid gout” in a reference to its occurrence in the elderly, PMR is unusual in those younger than 50 years. The annual incidence of PMR in those aged over 50 is between 12 and 50 per 100,000, with Caucasians afflicted more commonly than those of African or Asian ancestry.

PMR affects women twice as often as men and its incidence peaks between 70 and 80 years of age.

If left untreated, PMR can last for months to years before gradually subsiding. However, once identified, most straightforward cases can be managed within a primary care setting. PMR can be a challenge to diagnose but is often a rewarding condition to treat, largely because of its typically quick response to corticosteroids (CS) and favourable prognosis.

Although much has been learned about PMR since it was first described, its cause remains unknown. However, there is a growing body of evidence to suggest that its etiology, onset, and severity are multifactorial, resulting from a combination of age, environmental, and genetic factors (it is associated with certain HLA antigens).

The often acute onset of symptoms, resembling those of an infectious disease, suggests a possible viral element.

Clinical features of PMR include symmetric aching and stiffness in the shoulder girdle, neck and pelvic girdle regions, possibly accompanied by concurrent pain in the upper arms and thighs.

Shoulder pain is the most common complaint, reported by up to 95% of sufferers, with hip and neck discomfort affecting between 50 and 70%. Pain and stiffness is usually most severe in the first hour after waking or after a period of inactivity, but nocturnal symptoms are not unusual, with discomfort causing restlessness.

Musculoskeletal pain may worsen with movement of the affected area, meaning patients experience difficulty in performing daily activities, such as dressing, brushing hair or rising from a seated position. However, while examination may reveal a limited range of motion due to pain, passive range of motion is usually normal (barring the comorbidity of true arthritis).

Distal manifestations are present in up to half of patients and may include modest swelling of the knees, wrists or metacarpophalangeal joints, or carpal-tunnel syndrome. Pitting oedema of the dorsum of the hands, ankles and feet may also occur, but is uncommon.

Aside from musculoskeletal complaints, patients may present with systemic symptoms such as low-grade fever, fatigue and weight loss. In patients who experience a more insidious onset of symptoms, rather than the ‘sudden onset’ mentioned previously, systemic features may be more prominent (patients often describe these symptoms as being “flu-like”), making diagnosis more complex.

“PMR diagnosis is generally dependent on having a high index of suspicion, supported by history, examination, elimination of differential diagnoses and supportive laboratory findings.”

In the absence of any specific diagnostic tests, there is no definitive means of diagnosing PMR. Diagnosis is generally dependent on having a high index of suspicion, supported by history, examination, elimination of differential diagnoses and supportive laboratory findings.

Nevertheless, a variety of clinical diagnostic criteria sets have been suggested over the last 25 years, all of which have featured a combination of age, clinical features and an elevated erythrocyte sedimentation rate.

While none have received universal acceptance in the rheumatological community, a recent study comparing these criteria found the guidelines developed by Bird et al (1979) performed best with a sensitivity of 99.5%. The criteria are easy to apply in a primary care setting.

Of note, a primary finding in PMR is that treatment with low doses of CS (10 to 20 mg prednisone a day) produces prompt relief of symptoms. This response has proved so dramatic that a number of authors consider it a diagnostic criterion in its own right.

The most characteristic laboratory finding in PMR is an elevated erythrocyte sedimentation rate (ESR), also referred to as a sed rate. In more than 90% of PMR, the ESR is greater than 40 mm/hr (a normal ESR is 1–25), providing a strong indicator, in association with wider symptoms, for the condition.

Additional laboratory findings of systemic inflammation may also be noted, including an elevated C-reactive protein (CRP), normocytic normochromic anaemia, elevated platelet count, and elevated alkaline phosphatase. Myocyte damage is not a feature of PMR and consequently muscle enzymes such as creatine kinase are normal.

Because the clinical features of PMR are common, diagnosis partially rests on the exclusion of other diseases. Conditions such as elderly onset RA can show a PMR-like onset with prevalent involvement of the girdles, high ESR values, and good response to steroid treatment, so care must be taken to exclude more sinister conditions at the outset. Differential diagnostic conditions include:

- malignancies
- multiple myeloma
- rheumatoid arthritis
- fibromyalgia
- osteoarthritis
- myopathy
- myositis
- hypothyroidism
- shoulder problems (e.g. capsulitis or tears of the rotator cuff).

Should patients present atypically or if response to CS therapy is suboptimal, the diagnosis of PMR should be reevaluated.

“PMR occurs in about 50% of people who have GCA, and 15% of people with PMR will also develop GCA.”

While PMR is not dangerous in itself, it is closely related to a more serious condition; giant-cell (temporal) arteritis (GCA).

GCA is an inflammatory disease of unknown etiology that affects large- and medium-sized arteries of the extracranial branches of the aorta, originating from the aortic arch.

Inflammation of the arteries causes intimal hyperplasia, which leads to luminal occlusion and manifestations of GCA such as temporal headaches, intermittent claudication, scalp tenderness, and partial or complete loss of vision.

PMR occurs in about 50% of people who have GCA, and 15% of people with PMR will also develop GCA.

The precise nature of this association is poorly understood. As with PMR, the onset of GCA symptoms can be sudden or insidious and rarely occurs in patients younger than 50 years.

Patients with milder GCA features may complain only of generalised musculoskeletal discomfort and unusual fatigue, leading to a diagnosis of polymyalgia rheumatica. In any patient who presents with PMR, it is prudent to ask about headache, scalp tenderness and jaw claudication, as a consequence of untreated GCA is irreversible blindness, which can be prevented by prompt treatment with steroids.

The American College of Rheumatology criteria (1990) for the diagnosis of GCA are:

- age at onset of 50 years
- new headache
- abnormalities of the temporal arteries
- erythrocyte sedimentation rate (ESR) of 50 mm/h
- positive results of a temporal artery biopsy.
The presence of three or more of these five criteria gives a sensitivity of 93.5%.

Treatment of GCA usually involves high doses of corticosteroids, typically 40-60 mg of prednisone per day. This dose is usually maintained for one month and then slowly decreased.

The speed at which the dose is lowered may require adjustment if there are recurring symptoms of GCA of if the ESR rate shows significant rises. In most cases, the prednisone dose can be reduced to 5-10 mg per day over several months and discontinued completely after one to two years.

As with GCA, the cornerstone of therapy for polymyalgia rheumatica is corticosteroids.

Treatment typically starts at 10 to 15 mg daily, with the resolution of many symptoms within a few days to one week of therapy (a lack of improvement should prompt reconsideration of the diagnosis).

If improvement is shown, the initial dose is usually maintained for two to four weeks, then gradually reduced each week or two weeks by a maximum of 10% of the total daily dose. If the doses of CS are reduced too quickly, a relapse or recurrence of symptoms may occur, requiring a temporary escalation in therapy.

However, it should be noted that up to 50% of patients experience a PMR flare independently of the corticosteroid regimen. Regular assessment of clinical features and laboratory findings are a useful way of monitoring the situation.

Despite widespread agreement on the beneficial effects of corticosteroid treatment, data concerning the optimal duration of therapy is lacking. Most patients require six months to two years of low-dose CS therapy, but for some, prolonged corticosteroid treatment, sometimes for several years, may be necessary to maintain clinical improvement.

With adequate treatment, most patients are able to remain symptom-free. However, because long-term corticosteroid use can be associated with various adverse events, particularly in PMR’s generally elderly population, it is important to maintain follow-up.

Monitoring for potential omplications, including induction of osteoporosis, diabetes mellitus and infection, should be ongoing and several studies recommend giving calcium and vitamin D supplementation alongside CS therapy.

As PMR has been shown to precede the development of GCA, physicians should also remain vigilant for the development of symptoms. Any new headaches or visual symptoms should prompt immediate investigation.

While most cases of PMR can be contained within primary care, in some diagnosis and management can be difficult and these cases should be referred to a rheumatologist. Such patients may include those who show an inadequate response to steroids, who have repeated relapses or in whom the diagnosis is unclear.

At a glance: Bird et al criteria for diagnosing PMR (1979) Age over 65*

- ESR over 40 mm/hr
- Bilateral upper arm tenderness
- Morning stiffness of more than one hour
- Onset of illness less than two weeks
- Depression and/or weight loss.

The presence of any three of these criteria gives a sensitivity of 92% and a specificity of 80% for the diagnosis of PMR (Bird H, 2001). If an additional criterion of a rapid response to oral steroid therapy is added, sensitivity rises to 99% (Bird H, 2001).

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