Polymyalgia rheumatica

Recognition of polymyalgia rheumatica is straightforward and it is easily treatable.

Polymyalgia rheumatica (PMR) is an enigmatic condition, the pathology of which remains poorly understood.

However, recognition of the clinical presentation is often straightforward, and the diagnosis is supported by a rapid response to oral steroids, which is gratifying for both patient and doctor. Where the presentation is atypical or the response to steroids poor, further investigations and alternative diagnoses should be considered.

Who is affected?
The average age of onset of PMR is 70 years, but it virtually never occurs below the age of 50 years so that it would be wise to request a rheumatological opinion if the diagnosis is suspected in a younger person.

There is a female preponderance (approximately double that of males) and PMR has a relatively high prevalence in northern Europeans, suggesting a latitude effect, possibly indicative of an infectious trigger.

Presentation
Key symptoms are bilateral shoulder pain and stiffness, usually at their worst in the morning. Aching and stiffness of neck, lower back and thigh muscles are also likely to be reported.

In terms of function, patients have difficulty in raising their arms above their heads, turning over in bed, rising from sitting and getting up and down stairs. The history is often short: a few weeks or even days.

Systemic features including fatigue, mild fever, weight loss and low mood may be present.

Examination reveals tenderness of upper arm and neck muscles but retention of power. Ask the patient to mimic combing their hair and to stand up from sitting.

Differential diagnosis
A raised inflammatory ESR (or CRP) is supportive of the diagnosis of PMR but in a fifth of patients it falls within the normal range. So a normal ESR does not rule out the diagnosis of PMR.

Other blood tests that may be helpful in excluding other diagnoses include FBC, TFT, serum calcium, creatine kinase, RA latex, antinuclear antibody and serum and urine protein electrophoresis.

A normochromic, normocytic anaemia and raised alkaline phosphatase are consistent findings in PMR but creatine kinase is normal (in contrast to elevated levels in polymyositis, hypothyroidism and other muscle diseases).

The extent to which investigations will be undertaken will depend on the level of certainty of the diagnosis.

X-rays of cervical spine and shoulders may point toward a mechanical cause of symptoms. Investigations in secondary care might include autoantibody screening and muscle biopsy.

Treatment
There is no definitive treatment regimen for PMR but it is common practice to commence with a dosage of prednisolone 15mg daily. Arrange to review the patient a week after treatment initiation and if by this time symptoms have not been substantially eased then the diagnosis of PMR should be questioned.

Further investigation and/or referral on to a rheumatologist is appropriate, although if the clinical picture still strongly suggests PMR then the dosage of prednisolone may be increased to 30mg daily.

Treatment for PMR should be commenced urgently, as there is a risk of irreversible loss of vision because of the associated risk of giant cell arteritis (GCA), so treatment with steroids should not be withheld if the diagnosis is suspected.

The initial dosage of oral prednisolone 15mg daily is usually continued for around two weeks before reducing to 12.5mg daily for a further two weeks, and then reducing the dose further to 10mg daily.

Once a daily dosage of 10mg is reached then downward titration of prednisolone is slowed to 1mg every 6 to 8 weeks or so.

Follow-up and monitoring
Patients should be reviewed before each dosage reduction to ascertain whether or not symptoms of PMR have returned. Regular monitoring of ESR to assess disease activity is useful in conjunction with symptom assessment.

Even if dosage reduction proceeds smoothly it will be at least 18 months before a patient is free from oral steroids.

Often it will take longer then this as relapses are common, at which point the dosage of prednisolone needs to be increased (to perhaps double the dosage at which treatment failure occurred).

For some patients, complete withdrawal of oral steroids proves to be impossible and a long-term maintenance dosage has to be accepted.

If a high dosage of oral steroids is necessary to avoid symptoms then consideration should be given to using a steroid-sparing agent such as azathioprine and for this the patient should be referred to a rheumatologist. For those patients who successfully manage to withdraw from steroids arrange a review in three months with a preceding ESR.

Complications that might arise from long-term use of oral steroids include cataract formation, psychiatric reactions, hypertension, diabetes and osteoporosis. When reviewing patients for their PMR, periodically dipstick test the urine for glucose and check BP.

In view of the cumulative steroid dosage received, patients with PMR should receive bisphosphonate prophylaxis for osteoporosis (HRT may be an appropriate choice in perimenopausal women) along with calcium and vitamin D supplements from the outset of their diagnosis.

All patients prescribed steroids should receive a patient information leaflet and steroid card. Warn patients never to suddenly stop steroid therapy because of the risk of suppression of intrinsic adrenal corticosteroid production.

They should also be aware of the increased risk of infection and, in particular, the seriousness of contracting chicken pox or measles.

Giant cell arteritis
An estimated 20 per cent of patients with PMR have evidence of GCA and the two conditions are believed to have a similar pathogenic mechanism.

Symptoms suggestive of GCA include severe temporal (hence temporal arteritis) or occipital headaches, jaw claudication and scalp tenderness, as well as systemic disturbance.

If the condition is suspected prednisolone should be commenced at 40mg daily, most critically to prevent sudden loss of vision.

If visual disturbance has occurred an even higher dose of prednisolone should be commenced (60mg daily) and urgent ophthalmological review arranged with a view to temporal artery biopsy.

Dr Morris is a GP in Shrewsbury, Shropshire.

Differential Diagnoses
Mechanical

  •  Bilateral capsulitis or tendinitis of shoulder.
  • Osteoarthritis of neck or shoulder.

Connective tissue disease

  • Rheumatoid arthritis.
  • Polymyositis.
  • SLE.

Metabolic

  • Hypothyroidism.
  • Primary muscle disease.

Neoplastic

  • Myeloma.
  • Carcinoma.

Drug-induced

  • Statin myopathy.

Key Points

  • Suspect PMR in the elderly patient with bilateral shoulder ache and stiffness.
  • A raised ESR supports the diagnosis of PMR but a normal ESR does not exclude it.
  • Response to oral prednisolone should be rapid and profound. If this does not occur the diagnosis should be questioned.
  • Do not withhold treatment with oral steroids if PMR is suspected as there is a risk of sudden visual loss.
  • Down titration of oral steroids needs to be gradual and even then relapses are common.
  • Monitor patients for complications of steroid treatment and institute osteoporosis prophylaxis early after diagnosis.

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