Lucan · Conditions

Polymyalgia rheumatica

Australian guidance: eTG Rheumatology — PMR + GCA

1. Definition and epidemiology

Polymyalgia rheumatica (PMR) is a chronic inflammatory condition characterised by bilateral aching and stiffness of the shoulder and hip girdle areas, caused by low-grade synovitis of the periarticular bursae and synovial joints. It occurs almost exclusively in adults aged 50 years and over, with incidence increasing with age; women are affected approximately twice as often as men. Approximately 15 per cent of patients with PMR also have concurrent giant cell arteritis (GCA), making it the most important associated condition to screen for at every clinical encounter.

2. Pathophysiology

Per Robbins Ch 26, PMR is driven by innate and adaptive immune activation targeting synovial structures of the shoulder and hip girdles rather than muscle fibres, which distinguishes it from inflammatory myopathy. Interleukin-6 (IL-6) is markedly elevated and is the primary driver of the acute phase response responsible for raised erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP). Imaging with ultrasound and PET demonstrates that the structural correlates of girdle pain are bilateral subacromial, subdeltoid, trochanteric, and iliopsoas bursitis, combined with glenohumeral and hip joint synovitis. CD4 positive T helper cells accumulate at synovial sites and secrete interferon gamma and IL-17, amplifying the IL-6 signal. Muscle biopsy is normal or shows only type 2 fibre atrophy from disuse, consistent with the clinical observation that strength is preserved throughout the illness. The close epidemiological and pathological overlap with GCA, a granulomatous large vessel vasculitis, suggests shared dendritic cell activation in susceptible individuals; HLA-DR4 is a recognised genetic risk factor. The exact environmental trigger remains unknown, though seasonal clustering implicates infectious exposures.

3. Clinical presentation and diagnostic criteria

PMR presents with bilateral aching and prominent morning stiffness lasting more than 45 minutes, primarily affecting the shoulder and hip girdle. Patients often report inability to turn over in bed and great difficulty rising from a low chair or raising the arms above the head. Stiffness characteristically improves after a hot shower and with activity. Onset may be sudden or insidious. Systemic features including fatigue, low-grade fever, anorexia, and unintentional weight loss occur in approximately one third of patients.

The 2012 ACR/EULAR provisional classification criteria use a points-based system: bilateral shoulder aching, raised ESR or CRP, morning stiffness exceeding 45 minutes, new hip pain or restricted range of motion, and absence of rheumatoid factor (RF) or anti-cyclic citrullinated peptide (anti-CCP) antibodies. A score of four or more points without ultrasound, or five or more points with ultrasound demonstrating bursitis at two or more sites, classifies PMR with reasonable specificity. PMR is overdiagnosed in patients younger than 50 years, in whom the diagnosis is almost always incorrect. Important mimics that must be actively excluded include rheumatoid arthritis, spondyloarthritis, crystalline arthropathy, autoimmune myositis, fibromyalgia, statin-induced myopathy, Parkinson disease, hypothyroidism, and occult malignancy or paraneoplastic syndrome.

4. Investigations and AU-specific cutoffs

Diagnosis is based on clinical presentation combined with elevated acute phase reactants; there is no pathognomonic test.

Acute phase reactants. ESR greater than 40 mm/hour and serum CRP greater than 10 mg/L are expected and support the diagnosis. PMR is unlikely if both are normal, but up to 20 per cent of patients have a normal ESR at initial presentation. If ESR and CRP are not clearly elevated and symptoms are recent, eTG Rheumatology recommends retesting in one to two weeks rather than making an alternative diagnosis prematurely.

Full blood examination. Normocytic normochromic anaemia of chronic disease is common; thrombocytosis reflects the acute phase response.

Creatine kinase and aldolase. Both are normal, distinguishing PMR from inflammatory myopathy. Creatine kinase should be measured whenever proximal weakness is a prominent feature, as weakness is not a feature of PMR.

Autoantibodies. RF and anti-CCP antibodies should be negative. Positive results raise the differential of seronegative rheumatoid arthritis presenting with proximal symptoms in an older person.

Thyroid stimulating hormone. Hypothyroidism mimics PMR and must be excluded at initial workup.

Liver function tests. Mild alkaline phosphatase elevation is a recognised non-specific feature and does not indicate hepatic disease.

Imaging. Ultrasound demonstrating bilateral subacromial or subdeltoid bursitis supports the diagnosis and is incorporated into the ACR/EULAR classification criteria with a specificity-boosting effect. CT-PET is not required for uncomplicated PMR but may be warranted when occult large vessel GCA involving the aorta is suspected.

Temporal artery biopsy. Not indicated for isolated PMR without clinical features of GCA.

5. Management

The cornerstone of treatment is a prolonged course of corticosteroid therapy. Rapid symptomatic response within 48 to 72 hours is itself a good diagnostic indicator; failure to respond promptly should prompt reconsideration of the diagnosis. eTG Rheumatology emphasises that a long course is essential, and that rapid tapering significantly increases the risk of relapse, which paradoxically results in greater cumulative steroid exposure.

Initial dose. The eTG-recommended starting regimen for uncomplicated PMR is prednisolone (or prednisone) 15 mg orally once daily in the morning for four weeks. This is then reduced by 2.5 mg every four weeks to reach 10 mg daily, then reduced by 1 mg every four to eight weeks according to symptom response and tolerability until cessation. When constitutional symptoms are prominent or hip girdle involvement is severe, starting doses of up to 25 mg are appropriate. If GCA is concurrently suspected, doses of 40 to 60 mg are required and urgent specialist referral is mandatory.

Tapering and duration. Total treatment duration is typically 12 to 24 months. eTG guidance is explicit that regimens which taper and stop within nine months are associated with substantially higher relapse rates and should be avoided. Smaller and more frequent dose reductions are more effective at preventing relapse than larger and less frequent reductions.

Monitoring inflammatory markers during taper. ESR and CRP should be checked monthly for the first three months of therapy, then every two to three months thereafter or as clinically indicated. Transient rises in these markers are expected as the dose reduces and do not automatically indicate relapse; the clinical picture must be assessed concurrently. If a patient with otherwise well-controlled disease has elevated markers, consider intercurrent infection and retest after four weeks before escalating corticosteroid.

Relapse management. Approximately 50 per cent of patients experience at least one relapse during treatment. If relapse is confirmed, revert to the previously effective dose and taper over four to eight weeks back to the dose at which relapse occurred. Re-evaluate for concurrent GCA at every relapse. Specialist referral is required if relapse is frequent, corticosteroid therapy is poorly effective or cannot be tapered, or is needed beyond 18 months.

Exercise. Patients should be encouraged to maintain gentle activity and gradually increase the duration of exercise over time.

6. Pharmacology and AU PBS notes

Prednisolone (Panafcort, generics). First-line oral corticosteroid; available as 1 mg, 5 mg, and 25 mg tablets to allow flexible dosing. Starting dose 15 mg once daily for PMR per eTG; up to 25 mg when severe; 40 to 60 mg when GCA is suspected concurrently. PBS listed under general corticosteroid Authority prescribing.

Methotrexate (Methofar, Ledertrexate, generics). Steroid-sparing second-line agent for patients who relapse, require prolonged therapy, or develop early or severe corticosteroid adverse effects. The eTG-recommended dosage is 10 to 25 mg orally or subcutaneously once weekly on a specified day, combined with folic acid 5 to 10 mg orally once weekly on a different day. Oral bioavailability of methotrexate plateaus above 15 mg; subcutaneous administration is preferred at higher doses to improve absorption and reduce nausea. Evidence for methotrexate in PMR is conflicting but international guidelines support its use in practice. PBS streamlined Authority code 4185 covers methotrexate for severe resistant inflammatory conditions under specialist initiation.

Calcium and vitamin D. Mandatory co-prescription with any corticosteroid course expected to exceed three months. Calcium 600 mg twice daily with vitamin D 1000 IU daily; combination products such as Caltrate Plus are convenient. PBS listed under general calcium/vitamin D listings.

Bisphosphonate. Alendronate 70 mg once weekly (Fosamax, generics) or risedronate 35 mg once weekly (Actonel, generics) should be initiated when bone density is already reduced at baseline or when corticosteroid therapy is expected to exceed three months in patients aged 65 years or over. PBS streamlined code 4021 covers alendronate for prevention of glucocorticoid-induced osteoporosis.

Biological DMARDs. eTG Rheumatology does not recommend bDMARDs for PMR; evidence suggests they are less effective than methotrexate for corticosteroid dose reduction. Tocilizumab (anti-IL-6 receptor; 162 mg subcutaneously weekly or 8 mg/kg intravenously every four weeks) has shown promising results in some PMR trials but is not currently PBS listed for isolated PMR. It is PBS listed for GCA under streamlined Authority code 10982.

7. Complications and monitoring

Giant cell arteritis. The most serious associated condition. New-onset headache, scalp tenderness, jaw claudication, tongue claudication, diplopia, and transient or permanent visual loss must be screened for at every review. Anterior ischaemic optic neuropathy causing irreversible visual loss is the most feared complication of unrecognised GCA. When GCA is clinically suspected, high-dose corticosteroid and urgent specialist referral must not be delayed pending temporal artery biopsy.

Glucocorticoid-induced osteoporosis. Risk is proportional to cumulative corticosteroid exposure. Baseline DEXA scan is recommended; repeat at 12 months. Bisphosphonate and calcium/vitamin D should be initiated early in the treatment course.

Metabolic complications. Blood glucose monitoring is required in all patients, with increased frequency in those with pre-existing diabetes or impaired fasting glucose. Blood pressure should be checked regularly given that corticosteroids can exacerbate hypertension. Steroid-associated cataracts, mood disturbance, and skin fragility are recognised but less frequent adverse effects.

Relapse. Occurs in approximately 25 to 50 per cent of patients during taper. Patients should be counselled that transient aching and influenza-like symptoms are expected as the dose reduces and, unless advised otherwise by their treating doctor, they should persist with planned dose reductions unless symptoms persist beyond a few days or are associated with significantly elevated inflammatory markers.

Monitoring schedule. Review at four to six weeks after starting treatment, then every one to three months during active tapering, and every three to six months once a stable maintenance dose is achieved. Each review should include ESR and CRP, direct questioning for GCA symptoms, blood pressure, blood glucose, and clinical assessment for corticosteroid adverse effects.

Written for Australian practice and grounded in the guidance named above. Study material only — not medical advice. Always check against current guidelines.